Momus Design Cnc Router Manual Version 2.1

MomusDesign

BENCHTOP CNC ROUTER PLANS v.2.1

Version 2.1 © copyright 2013 All rights reserved release date: March 30, 2013 www.momuscnc.com

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preface introduction machine specifications design goals CNC basics CAD/CAM workflow electronics enclosure design alterations structural design bill of materials parts list & schedules exploded views drawing sheets wood parts fabrication wood parts assembly metal parts fabrication metal parts assembly epoxy bed levelling cover installation electronics installation The purchaser of this document has express permission from the author to print a hardcopy for personal use only. This document may not be resold, distributed, or used for commercial gain. Commercial sale of components or assemblies derived from the information herein is forbidden without prior licensing agreement with Momus Design. IF THIS DOCUMENT HAS BEEN PURCHASED FROM ANY SELLER OTHER THAN MOMUS CNC, IT HAS BEEN AN UNAUTHORIZED AND ILLEGAL SALE. Please report any such activity to Momus CNC.

Xylotex installation Gecko G540 installation limit switches Mach3 setup machine alignment spoilboard first use suppliers ADDENDUM: Z axis thrust bearing

table of contents

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Preface to the 2nd edition Welcome to the second edition of the Momus Design CNC router plans. The machine described in these pages is an evolution and refinement of an earlier design, with numerous and significant changes throughout. The original machine was designed and constructed in 2008‐2009, with the plans debuting in the summer of 2010.

Bob Pavlik ‐2012

BENCHTOP CNC ROUTER PLANS

Many of the design improvements represented in this second edition would not have come about without the input and feedback of all those builders who constructed the first version of the machine. Especially significant was the communication between builders and myself that was made possible by the formation of a dedicated sub‐forum on CNCzone.com (http://www.cnczone.com/forums/momus_design_cnc_ plans/). The existence of this platform has become and integral and important aspect of both this design and the plans progressing forward. Please consider this as a welcome invitation to become a part of this community of builders and observers.

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After several years of using the machine, and following the progress of others who were constructing their own copies from the plans, it became apparent that there were many areas that could be improved. By the summer of 2011 it was felt that there were enough desired changes to warrant a full re‐design and refinement of the original concept.

version 2.1 copyright 2013

preface

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Introduction The machine plans contained in this book perhaps bear one significant difference from many others that are available. The difference is that these plans were not put together with the goal of selling plans. They are the by‐product of building a machine that came into existence because of the need for a functional tool.

Disclaimer: The author of this design is not a professional engineer. This manual outlines the construction of a hobbyist machine, designed and built by a hobbyist. Also note that CNC equipment can be dangerous machinery. In addition to the inherent dangers of operating any power tool, doing so remotely, via computer, adds another level of potential danger. Errors in programming machine movement can have catastrophic consequences.

So began the journey of designing and constructing my own machine, a process which ended up consuming several years. The resulting machine has far exceeded my initial expectations. The machine has performed superbly, proving capable of milling materials not typically handled by low cost DIY machines (such as aluminum,) and having accuracy that far surpassed original design goals.


The design of this machine began as many others surely do: by studying existing solutions with the intent of creating a copy of the best currently available. Unfortunately, none of the existing home‐built small‐ format CNC routers seemed suited to my particular needs and constraints. With a small workshop space available, limited equipment with which to build, the need to keep dust and noise contained, and a very meager budget, the existing options were quite limited.

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The design and fabrication of this machine was due to a specific need, primarily the building of models for architectural research, that focused on digital design processes and construction automation. The inherent nature of this research required the use of CNC machinery. Despite having access to large format CNC equipment, the flexibility of having a home‐workshop based tool seemed to be greatly advantageous.


It is the responsibility of the reader to use the information presented in this manual in a manner deemed appropriate to personal judgment and safety, and use at your own risk.

introduction

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Machine Specifications:

ACCURACY Mechanical accuracy: Precision (repeatability):

+/‐ .005” +/‐ .001”

MACHINE CONSTRUCTION MATERIALS Machine base: Plywood Mechanical parts: Aluminum and steel. The machine is built entirely from standard stock material sizes of plywood, aluminum and steel. The stock material thickness is used for all critical dimensions. Materials were chosen for this design in order to give the highest possible machine rigidity for the cost. No MDF (medium density fiberboard) is used in the construction of the machine, as it is too flexible to result in a machine of adequate stiffness. DIMENSIONING Plans are dimensioned in Imperial measure. They are NOT currently available in metric. While the plans are not available in metric, numerous machines have been constructed in countries that use metric measure. This can be done either by adapting the plans for locally available metric sizes of materials, or by sourcing materials from the US (see list of suppliers at the end of the plans.) DRIVE METHOD X and Y‐ belt drive Z‐ precision acme leadscrew with anti‐backlash nut Belt drive can use either open‐ended belting or a closed belt, depending on availability. Z‐axis anti‐backlash nut is a commercially available product.

ADJUSTABILITY AND ALIGNMENT All bearings are provided with a micro‐adjustable setscrew for precise and easy adjustment. The design of the machine is based around a step by step alignment procedure, that allows for highly accurate setup with very simple tools. SPINDLE The machine is intended to use a trim router, such as the Bosch Colt, or Ridgid R2400/2401. MACHINE SPEED Jogging speeds of over 500 inches per minute. STEPPER MOTORS NEMA23 frame size. Minimum recommended size‐ 275 oz./in. RESOLUTION At 1/10 microstepping: X and Y axes‐ .001” Z axis‐ .0000625” Note that electronic resolution is not an indicator of the accuracy of the machine. However, it is a potential indicator of the speed of the machine. The finer the resolution, the slower the machine. MATERIALS THAT CAN BE CUT Wood Plastics Foam Aluminum Brass Circuit Boards Note that although the machine is capable of cutting aluminum, this machine is designed and intended primarily as a wood router. Spindle speeds of trim routers may limit the type of work that can be accomplished in materials other than wood.

Machine specifications

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Exact usable Z axis travel will depend on exact configuration of router mount, length of router bit, and thickness of spoilboard beneath the work piece.

LINEAR MOTION All axes are controlled by standard ABEC7 bearings riding on rectangular cold rolled steel rails.


MACHINE SIZE cutting envelope‐ 16” x 16” x 5.5” overall machine size‐ 32.5”wide x 27.5”deep x 26” tall.


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Machine Design goals When this machine was designed, a list of goals and criteria were established at the very beginning of the design process. The overall goal was to create an inexpensive machine that could be fabricated in a home shop and perform like a machine costing many times more. Cost: The machine needed to be as inexpensive as possible, while meeting as many other goals. Target build budget was $400, excluding electronics. Tools: Construction had to be possible with minimal tools and equipment. It had to be constructable with basic tools that would not have a high level of accuracy in themselves. This would require creative build techniques to fabricate a machine that was more accurate than the tools used to build it.

Speed: Cutting speed needed to be considerably higher than most other inexpensive DIY machines, which often only moved at 20‐30 inches per minute. To facilitate running programs that contained tens of thousands of lines of code, a target speed of 150 ipm was set. Alignment: Many existing home‐built designs had no simple way of attaining accurate machine alignment. An easy alignment procedure was considered integral to a successful to a design. Bind free: As many existing designs had no way of being accurately aligned, they also often suffered from binding. Linear motion components that could not be brought into being exactly parallel or in‐plane would cause the machine to bind during travel along its axes. This binding could cause lost steps in the drive motors, potentially ruining a work piece.


Enclosed: Due to where the machine would be used, it was necessary to have a full enclosure to contain dust and sound.

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Accuracy: It needed to be able to cut to a tolerance of about +/‐.005". Higher accuracy wasn't deemed necessary as the machine was primarily intended to cut wood, which is not a material with high dimensional stability. However, a high enough accuracy was required to allow machining of mating parts that would be assembled, which requires more accuracy than simply carving or engraving a single piece.

Self‐contained: All wiring and electronics should be organized into a single unit, rather than having external components. Compact: To allow for easy use of the machine at different locations, it must require little or no disassembly/reassembly for travel.


Attractive: The machine must be attractive and look more like a commercial product than something that was cobbled together.

design goals

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Desktop Manufacturing

However, having the ability to easily have these manufacturing capacities available raises questions of appropriate use of technology. If a part can adequately be made by more traditional hand crafted methods, it may be an inefficient use of time and resources to use a computer controlled machine. In addition to the initial time invested in machine construction, the fabrication of a part can require significant time spent at the computer. Even a simple part requires drawing or 3d modeling it, deciding on a machining strategy, generating toolpaths and G‐code from the drawing, and setting up the stock to be cut on the machine. The advantages comes in using the equipment for purposes that cannot be achieved easily by other means. CNC lends itself to jobs requiring high levels of accuracy, consistency between repetitive parts, and cutting complex geometries. These advantages are significant, and potentially transformative, for both hobby and business use.

More recently there has been a tremendous growth in Do‐It‐Yourself (DIY) home‐built CNC equipment. It is now a relatively straightforward process to generate the code (“G‐Code”) to control a CNC machine tool on a home PC, and output the signal through a parallel port or USB port to motion control motors. Depending on how complex and sophisticated the geometry of the parts being manufactured, this can even be accomplished with free software.

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In the early development of CNC, the numbers that were used to control a machine were hand‐coded and punched into a paper roll that was fed through a mechanical reader. The punched holes equated to discrete movement steps. While programming simple movements, such as straight lines, was easily accomplished, curved or free‐form geometry was much more difficult to achieve. With these complex shapes, the smaller the distance between the motion steps, the smoother the results, necessitating the calculation of thousands of movement points. With the advent of the computer came the ability to generate much more complex numerical code, resulting in very smooth machine motions.

The potential implications for this revolution in “desktop manufacturing” are huge. Transferring the manufacture of extremely complex parts from costly industrial settings, which was the only option in the recent past, to a low‐cost home shop opens up a world of possibilities. Many of the machines that have been constructed from the plans in this manual have found use in small home‐ based manufacturing businesses.


What was once a technology that existed strictly within industry, CNC (Computer Numeric Control) equipment has increasingly found widespread use in the home workshop. At its most basic, CNC is a method of using a numerical code to control a machine. Nearly any type of machine or configuration can be controlled this way. If it has a range of movement, whether linear or rotary, it can be controlled by a numerical code that instructs those movements. Therefore, CNC can be used on a wide spectrum of equipment, such as milling machines, lathes, plasma cutters, water jets, hot wire foam cutters, wire EDM, etc. Or, as is the case with these plans, a 3‐axis wood router.


CNC basics

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SOFTWARE WORKFLOW

Design parts in software such as AutoCad, Rhino, Solidworks, TurboCad, etc...

TOOLPATHS (CAM) Generate movement of the cutting tool in software such as: MasterCam, RhinoCam, BobCad/Cam, etc...

MACHINE CONTROL Send cutting tool information to the machine with software such as: Mach3, emc2, TurboCNC, etc..

Creating the geometry for complex three dimensional surfaces requires a much more advanced software than is necessary for simple 2d linework. Software such as Rhino3d, Solidworks, or Inventor are powerful 3d modeling tools designed specifically to manipulate sophisticated topographical geometries. Cutting these surfaces is considered full 3d milling, as the Z axis of the spindle is moving in careful coordination with the X and Y axes to result in the desired shape. These surfaces are exported in file formats that preserve their topographical data.

1. Machine definition. The software needs to know the configuration of the machine itself. While many of the more basic programs are only capable of 3 axis milling, more advanced software can handle more machine axes, or alternate configurations of how those axes move. 2. Stock setup. The software needs to know how large your piece of stock is, so that it can calculate how much material might need to be removed from around the final part. This is less important in basic 2 ½ axis milling, where it often really does not matter how large the stock might be, as long as it is sufficiently large to allow clamping to the machine bed at a safe distance from the cutting path. Stock size is much more crucial when doing full 3 axis milling, as the increased amount Z axis movements creates more opportunities for collision between the cutting tool and the stock. So again, this is a situation of needing to match the abilities of your software to the types of parts that you want to make. Complicated parts may even need to have additional geometry drawn in the design software, to provide additional cutting surfaces to remove material for needed tool clearance. There are a couple of typical ways to enter stock size information within CAM software. One is to enter coordinates for the corner points of your stock size. Better CAM software can automatically detect the boundary size of your part and generate a stock size around that. In this case, it is often desirable to draw the uncut block of material in the design software, so that the CAM software creates the desired material size.

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DESIGN (CAD)

Designing parts to mill Parts that ultimately will be cut with the machine need to originate somewhere, and that typically happens within some sort of CAD (Computer Aided Design) software such as AutoCad, Rhino3d, Solidworks, AutoDesk Inventor, TurboCad, or even software such as Corel draw. This software may be either a 2d or 3d environment. The type of software required will be driven in large part by the type and geometric complexity of the work being designed. Very simple parts that are being cut from sheet stock can be designed in very rudimentary software that merely allows you to accurately draw two‐dimensional lines and export that information in an appropriate file format. Cutting parts of this nature is often referred to as 2 ½ axis milling, as most of the machine motion happens within only 2 axis. The spindle only moves up and down in the Z axis to enter the work at the beginning of the cut and to lift itself clear of the material at the end. Simple parts can be designed in one of the many freeware 2d drafting software packages available, as long as the design can be exported in a file format that is compatible with other software that will be used downstream in the workflow (the CAM software).

Toolpaths The next step in the CAD/CAM workflow is typically to generate toolpaths, or the movements of the machine that are necessary to cut your part. This can happen in CAM (Computer Aided Manufacturing) software such as Mastercam, RhinoCam, MeshCam, MadCam, or a range of other programs. The following are basic steps that are often part of the workflow within a CAM software package.


CAD/CAM Workflow


CAD = Computer Aided Design CAM = Computer Aided Manufacturing

CAD/CAM workflow

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There are two methods of determining feed rates. The best method is to do a “chip load” calculation, which takes all of those factors above into account. The principle of this calculation is that it provides for an ideal quantity of material to be removed by the tool's cutting edge each time it moves through the material. This quantity is often published by the manufacturer of the cutting tool. This calculation will give a fairly accurate number for setting feedrate. The other method is an empirical process, where experience can provide an equally good feedrate number, or can aid in fine tuning the number that is arrived at by a chip load calculation. Unfortunately, in practice many other home‐built machines require neither method. They typically have a maximum travel speed that is far below running any danger of going too fast. So they can often simply be run at the highest feedrate that the machine will allow. If anything, many home‐built machines often have the problem of running so slowly that they can cause a poor surface finish, or even damage to the part or cutting tool, because they do not remove material quickly enough to keep the cutting edge cool When cutting wood this can cause burning of the material. 5. Toolpaths. The next step is typically to generate the actual paths that the tool will follow. With simple 2 ½ axis cutting this is a very simple process without many factors. Primarily all that matters is the size of the tool. More complex 3d cuts open up a wider array of cutting options. Complex parts may require determining a logical cutting strategy, to remove material in a series of stages that will result in the best surface finish or require the least time.

Plunging When milling part geometries where the tool can not simply enter the workpiece from the edge of the stock, such as when cutting a pocket, the tool needs to make some type of descending cut into the material. The simplest method is to move the tool straight down into the material, which may or may not be the most appropriate movement. Many cutting tools are not designed to be plunged straight down into material in such a way. A tool that can accommodate this move is referred to as “end‐cutting,” and can cut on its tip as well as its side. When the tool cannot be plunged, the tip will need to be gradually lowered into the stock as it is simultaneously moved in a sideways direction. This is called “ramping” into the material. The best CAM programs provide great control over how the tool can be ramped down into the material, including straight ramping and helical moves. It may also be desirable to avoid straight plunge cuts due to material properties. The grain of some woods may tear under such a tool movement. Direction of cut Any amount of experience with a hand‐held router will quickly reveal the difference between moving the tool from left to right and right to left along the edge of a piece of material. One direction will be much harder to control. With a hand‐held router you would typically move left to right to maintain the greatest control of the tool. This is called conventional milling. If moving in the other direction (“climb cutting”) the router bit may grab into the material and be pulled in an undesirable direction. However, when controlling the router with a machine the situation is not so simple. Depending on the circumstances, climb cutting may provide a much finer surface finish.

CAD/CAM workflow

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4. Cutting speeds and feeds. Depending on numerous factors (the type of material being cut, the type of cutting tool, the rpm speed of the spindle, how much of the tool is being engaged in the material, and the quality of finish desired), the feedrate must be set for how fast the tool is pushed through the material. On most home‐built machines the spindle speed is set at the router itself, so that does not need to be controlled through the software. The feedrate must be fast enough that the tool can efficiently eject the cut material away from the cutting area.

Roughing vs. Finish When removing large amounts of material quickly, a “roughing” cut is often used. This is a fairly aggressive cut designed to remove stock around the final geometry quickly and efficiently. It may have the tip of the tool engaged deep into the material, and when multiple parallel passes are required it may step over as far as the entire diameter of the tool between each pass. The roughing cut will typically then be followed by a finish cut which removes a much smaller final amount of material, both in depth of cut and distance of step‐over between passes. There may even be a change of cutting tools between the roughing and finish cuts.


3. Tool size. The software needs to know the diameter and shape of the cutting tool. Many CAM packages have a library of tools from which you can pick the size and shape of your cutting bit. In others you may need to enter this information manually.


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While G‐code is a standard language, unfortunately each machine controller software often uses its own variation. The machine control software typically used by the home‐ builder runs on a version that is often very close to pure (canonical) g‐code. More specialized machinery, which has its own control electronics rather than using a PC for control, often has a correspondingly more specialized version of g‐code. Similar to the need for matching the design software to the type of parts that you want to create, it may take some necessary care to match CAM software to control software. Problems may be encountered with finding CAM software that can handle generating toolpaths for complex geometry, yet has proper post‐processing ability for control software such as Mach 3 or emc2, which are typical of what is used by the home user. Software that will accommodate very complex geometry may only have posts available for more industrial machine controls. This might mean learning enough g‐code to be able to manually edit and alter post‐processed code for use in PC based control software.

Software overlap Often, software use isn’t quite as direct as the workflow diagram might indicate. Many CAM software programs provide tools for doing basic CAD work. While this can be handy for making minor changes after importing geometry to the CAM program, it is rarely powerful enough to use it as the sole design tool. Anything more than minor changes are best done back in the original design software, and then re‐exported to the CAM program. Similarly, control software sometimes has basic tools for conversion of .dwg format line drawings to g code. Again, this isn’t the primary job of the software, so while it may work adequately for very simple jobs, it should not be relied on exclusively. Control software typically also contains a g‐code editor for manipulation of the code.

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7. Post‐processing. Once all of the above steps have been finalized, and the operator is content with the toolpaths, the final step is “post‐processing.” This is where the software converts all of the toolpath information into a format that can be read by other software that will control the movements of the machine itself. This is typically some variation of an industry standard language called “g‐code”, which is a simple text file. G‐code is nothing but a line by line set of numerical instructions for the machine to follow. It gives tool movement information in absolute coordinates, and may also provide information such as feedrate and spindle speed, and on more advanced equipment, moves such as automatic tool changes.

Machine Control software Mach 3, emc2, TurboCNC This software takes the code that was generated by the CAM software (g‐code) and outputs it as electronic signals that actually control the motors on the machine. This typically happens by sending “pulse” and “direction” signals through a parallel port cable to the machine electronics. Mach3 has come to dominate the DIY CNC market, as it is a very robust program and is affordably priced. Many people use the free demonstration version of the software, but it is recommend to purchase the full version if funds allow. The demo is crippled to running 500 lines of code. This might seem like a lot, and might be sufficient for milling very simple parts with mostly straight cuts, but it will quickly be found to be severely limiting for cutting anything more complex. Even small parts with very complex 3d shapes may easily require tens or even hundreds of thousands of lines of code. Another less known, but just as important, restraint of the demo version is that it limits the processing speed of how quickly it outputs signals to your machine’s motors. This can directly limit machine performance.


6. Simulation. Many CAM programs have a simulation feature which will allow viewing a 3d computer simulation on the computer screen of the tool cutting the material. This can allow watching if the tool is moving in desired directions and sequences, and if there are any possible collisions between the machine and the stock. The best CAM programs will automatically detect these collisions and provide a warning.


CAD/CAM workflow

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Learning G‐code Another alternative when cutting simple parts is to hand write g‐code. Doing this can eliminate the need for both design software and CAM software. Before the development of sophisticated CAM software, this was how numeric machine control code was generated. The number of applications of this technique are probably limited these days, but it can be a useful method to know. Even if hand writing numeric code is not a primary working method, understanding the G‐ code language can be useful as it can allow quick editing or modifying parts of the code such as feed rates, without having to go through the post‐ processing step again. Combined with other computer programming skills, learning g‐code could also allow writing scripts to generate toolpaths and g‐code from within 3d modeling software such as Rhino.


While software with advanced functionality can be very expensive, there is a substantial and growing quantity of lower budget programs available. Some of these are even free. While they are often lacking certain features, a significant amount of complex work can often be achieved with then by employing some creativity in how they are used. Workarounds can often be discovered that can compensate for functionality that they may lack. The supplier list at the end of this manual includes a list of software suppliers.

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Cost of software As might be surmised by this point, the cost of the software necessary to design, generate toolpaths, and then control the machine can be very, very expensive, especially if needing to create parts of any complexity. Before constructing a CNC machine, it is highly recommended to look into the costs of the software programs that might be required, as they can easily far exceed the budget for machine construction. Most software vendors have functioning demonstration versions available for download, and it is also recommended to try them before purchasing. Some are much more user friendly and intuitive than others, which have very steep learning curves.


CAD/CAM workflow

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computer

While specific components of an electronic drive motion control system for a homebuilt CNC machine can vary widely, the abstract diagram to the left illustrates the basic principles of what is included. In general, these are:

motor drives & power supply

machine motors

1. A computer to send motion data to a hardware component called a “motor drive.” 2. A power supply to provide the required voltage & current to the motors. 3. Electronic motor drive(s) that forwards the motion data to the motors at the required voltage/current. 4. The motors. This is the general flow of information from the computer to the motors. In addition, there are typically hardware components to provide data feedback from the machine to the computer. All systems should be equipped with limit switches at the end of each axis travel, to provide safety to both the machine and operator. More sophisticated drive systems may have feedback sensors that give more accurate control of the motor positioning. Working backwards from the motion of the machine: Motors Most home‐built machines are controlled by stepper motors. These are simple type of DC motor that requires a pulse of electricity to move it one “step”. A typical stepper motor has 200 steps per revolution, so to cause continuing rotation in a stepper motor it requires a fast stream of discrete electrical pulses. The frequency of the pulses will determine the motor speed.

These motors are easy to electronically control via computer, and relatively inexpensive, but they do have some drawbacks. One is that there is the possibility of them “losing steps” under a load. This happens due to the stream of electrical step pulses continuing to flow to the motor even though it is temporarily being prevented from moving. Since the number of steps required to move the machine is very high, a very small number of missed steps may not have any noticeable impact on the finished part. On the other hand, enough missed steps may be catastrophic. In the best case, it may result in a less than perfect part, and at the worst it may result in machine collisions, since after the event that causes lost steps the machine location is not corresponding to where the software thinks it should be. Missed steps is a problem with stepper motors because they typically lack any sort of feedback mechanism. They simply do as they are told, and the control software has no way of recognizing any error that may occur, or way of correcting the motion. Some more advanced systems employ a sensor that informs the software of the position of the motor or machine, so that it can compensate for any deviation and return it to proper location. Another problem that steppers often suffer from is “mid‐ band resonance.” This occurs when the frequency of step pulses causes a dynamic resonance within the motor. This may cause it to move erratically or even lock up completely. This is obviously an even bigger problem than a few missed steps. Some stepper drives have circuitry that is designed to combat this phenomena. Many hobby level drives do not. Many industrial machines use servo motors rather than steppers. They do not run in discrete steps like a stepper motor, but rather are more similar to a conventional motor design. These can be either DC or AC designs, and typically run at a much higher rpm than steppers, necessitating a gear reduction of some sort. Due to both of these factors, servo motors consequently have a much smoother operation than steppers. The major advantage of servos is that they typically have a positioning feedback loop. They employ a device called an “encoder” that monitors the position of the motor. Any discrepancy between the theoretical position of where the motor should be, and where it is measured as being, can be compensated for, and brought back to the correct position. However, servos are still much more expensive systems to set up on a home‐built machine. They require more sophisticated electronics equipment to drive them and more knowledge to set them up and “tune” them.

machine electronics basics


While an in‐depth discussion of machine control electronics hardware is beyond the scope of these plans, an overview is important for a basic understanding. For the most part, this discussion will stay somewhat abstract, although in the machine assembly instructions the specific installation of two types of drive boards, a Xyoltex and a Gecko G540, will be covered. Due to the complexity of choosing individual components that will function well together, it is highly recommended to purchase a pre‐packaged kit from a supplier that includes all of the electronics as a matched collection.

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Electronics


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Torque curve & power transmission

A belt drive was also felt to be advantageous over a lead screw system for this machine as it is more tolerant of misalignment. A lead screw must be aligned exactly parallel to the machine axis it is powering. By contrast, the belt can be out of alignment by a significant amount, with zero negative impact on machine accuracy or performance. Note that misalignment will have a significant negative impact on belt wear. Drives All motors that are used for motion control require some type of electronic drive board to control them. Drive boards take a variety of arrangements. They may incorporate control for several axes on a single board, or may be configured as an individual board for each axis. The advantage of an separate board per axis is that they can be replaced individually in case of damage.

Microstepping Another function of many drives is that they break up the number of steps per revolution that are required at the motor into a greater number. So for instance, a drive may have “1/8” or “8x” microstepping, which would effectively increase the number of steps per revolution that control the motor from its original 200 to 1600. This is advantageous in that it increases the resolution of the system and provides finer control over the movement of the machine. Note that these micosteps are typically not an exactly equal sub‐ divinding of the original 200 steps. Each microstep may vary from the others by a very small percentage. This discrepancy is typically so small that it is inconsequential and will not adversely effect the accuracy of the machine. However, when including microstepping in the calculation of machine resolution, it should be understood that this number has a very slight variability within it. Power supply This is as simple as it sounds. A transformer type power supply device is matched to the needs of the drive board(s) and motors. It is worth noting that many boards that operate by “pulse width modulation,” such as the Xylotex, actually perform most efficiently at the upper limits of voltage that they can handle. In other words, running them at lower voltage will not necessarily provide any additional protection for the drive board. Stepper motors also commonly require many times more voltage than their ratings may indicate. For instance, a stepper motor that is designated as a 2.5 volt motor may require a 24 volt power supply to efficiently power it.

electronics

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The belt drive system on this machine was designed with exactly these factors in mind. It is felt to be a good compromise between machine speed, power available to push a tool through the material it is cutting, and avoiding motor speeds that would be vulnerable to mid‐band resonance.

All drive boards do essentially the same thing. They receive input signals from the control software, which are low in voltage and current, and in turn output these signals to the motors with higher voltages and currents that they require for operation. As such, they mediate between the computer and the machine. Their in‐between position also allows them to handle signal inputs for additional functions such as emergency stop buttons and limit switches. Most drive boards are very vulnerable to any errors in mis‐wiring. Incorrect connections, or breaking a connection to the motors while under power, can cause an immediate destruction of the electronics on the board. Follow manufacturer directions very, very carefully.


Like all electric motors, stepper motors have the characteristic of producing the greatest amount of torque at zero rpm. What this means is that the faster the motor turns, the less force it produces. Manufacturers provide graphs that show their motors torque output relative to rpm. Not all motors are created equal, as some have torque output that falls off much more quickly relative to rpm increase than others. Therefore,when designing a power transmission system it is crucial to know what rpm the motor will be turning for a given movement speed at the machine. “Gearing down” the system may not necessarily increase the machine’s “power” as the decrease in the motors available torque at a higher rpm may be greater than the mechanical advantage that is gained through gear reduction. However, even though the motor produces most torque when barely turning, the machine cannot be geared to maintain the motor at that speed. If the motor is turning that slowly then the distance between each “step” of its movement will translate to too large of a movement at the cutting tool. It will not have a fine enough cutting resolution. So the system becomes a compromise between several factors.


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MomusDesign

Additional switches Drive boards or breakout boards will furnish some means of wiring in several important additional devices. An emergency stop button should be part of every system. It is typically a large red button with a mushroom‐shaped head, that provides an immediate way of shutting down the machine in case of an emergency. It should be placed in a location that is easily accessible while operating the machine. It can be wired to shut down all axes of machine movement, and can usually also be wired to shut down power to the router to kill the spindle movement. If at all possible, your e‐stop button should be wired in this manner.

The computer All of these inputs and outputs either originate or terminate in the control software in the computer. Most control software for home‐built machines is written to be used on PCs, although Mac versions are becoming available. The most popular, Mach3, is designed for Windows based machines, and others such as emc2 are Linux based. A computer with a parallel port for output to the machine electronics will typically be required. The computer need not be the latest model, and in fact an older model with Windows XP or even Windows 98 may be preferable with some software. A desktop model is generally better than a laptop, as most laptops do not have a high enough voltage output through their parallel ports (if they even have one) to perform well. They also often have power saving features to extend battery life, which interfere with the pulse timing of the control software.


Breakout board Simple drive boards, such as those that have multiple axes self‐contained on a single board, may be designed for direct connection to the computer’s parallel port via a standard cable. When using multiple drives that each control an individual axis, an additional piece of hardware called a “breakout board” may be required. This is merely a device that connects to the computer via a cable (typically parallel port) and then provides multiple connections to allow wiring to the drives, emergency stop stop switches, limit switches, spindle control relays, etc. These boards also often provide an added layer of protection between the higher voltage drive boards and the vulnerable low voltage computer. They do this through optically isolated connections.

The other switches that should be wired into the system are limit switches. These are placed at the end of each axis’s range of movement, thus a 3 axis machine will typically have 6 switches. A limit switch on the Z axis, in the direction of movement toward the machine bed, may be omitted as it would require frequent repositioning due to changes in stock size, cutting tool length, etc. These switches will stop the motion of the machine if it unexpectedly reaches the end of a travel axis. This can prevent serious damage to the machine as well as guarding against personal harm from broken cutters. In addition to acting as safety devices, these switches can do double duty as homing switches. These are used to return the machine automatically to its home XYZ position. Most control software can be configured to use the switches in this manner.


electronics

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14

Machine enclosure and sound transmission principles

The other type of sound control is between adjoining spaces. This is sound transmission. An example of this would be a situation such as adjoining rooms in a building, where it is desirable to have as little sound make its way from one room to another. This is a completely different situation from controlling sound within a space, and this is the type of sound control that the machine enclosure must provide, preventing the transmission of sound through it. The foam insulation used by many builders is not intended to control sound transmission, therefore it would be of significant use only if a listener were placed inside the machine enclosure. Otherwise, it will mostly serve to collect a lot of dust. There are three primary categories with which sound transmission can be controlled: 1. Distance 2. Isolation 3. Mass

The second category is very important when it comes to machinery. Vibrations can be transmitted through materials and cause new vibrations to be produced a distance away. These new vibrations produce sound. To combat this tendency, many pieces of equipment have isolation mounts that damp vibrations. These may be comprised of springs, hydraulic devices, or elastomeric materials such as rubber. Even if all sound could be contained within an enclosure, bolting the machine rigidly to a bench could have the effect of turning the bench top into a large sounding board. The third category is the one that is of primary importance to this design. Increasing mass is a very effective way of preventing sound transmission, therefore the ideal situation is to make an enclosure out of a thick, massive material. This has its obvious problems, such as weight, needing to open the enclosure, and needing to provide windows to see in. The window material will have a low mass, increasing the sound transmission of the enclosure as an overall assembly. Thicker window material can be used, at an increased cost. What is of most interest is a sub‐category of the principle of increased mass, and that is the removal of any gaps or cracks. A gap is a zone of zero mass and has a major consequence on sound transmission. It has such an impact that a 1/32" wide crack in the wall of a room can allow more sound through than the entire rest of the wall. To combat this, the enclosure must be thoroughly sealed. The tighter it is, the more effective it will be at preventing sound transmission. Some home‐builders who have installed a foam lining claim an improvement. Small gains may be seen for a couple of unintentional reasons. Depending on how it is attached, it may be preventing surfaces of the enclosure from vibrating and producing sound. In effect it is providing some damping. More importantly, it is helping with the mass issue. While it provides a small amount of direct additional mass, it is covering up crucial gaps. Unfortunately, better results could most likely have been achieved with a simple roll of tape or tube of silicone caulk.

sound control

MomusDesign

There are a couple of different types of “sound control.” First is the controlling of sound within a space. Sound waves bounce off of surfaces and it is often desirable to have a certain type of control over how this happens. The more times a sound bounces off of surfaces before it reaches a listener's ear, the longer the “reverberation time” is considered to be. Sometimes a longer reverberation time is desirable, such as in a concert hall, and at other times a short or zero reverberation time is needed, such as in a recording studio which must be free of echoes. Lining walls and ceilings with a material that absorbs sound waves will prevent them from being reflected back to a listener, and makes the space more acoustically “dead.”

The first category is obvious. The farther away a sound is placed, the quieter it is going to be. This category clearly isn’t of much help in designing a machine, as it can't simply be placed farther away.


One of the important considerations while designing this machine was the necessity for it to be enclosed, for the containment of both dust and noise. There are many existing examples of home‐built machines that have also included a cover for these reasons. However, there generally seems to be a fundamental misunderstanding of the basic principles of sound control. This is evidenced by the technique that many of these builders have adopted: lining the inside of the enclosure with foam‐rubber acoustical "insulation” of the type with an “egg‐crate” texture. Unfortunately, this is an incorrect application of this material.


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The following section outlines design information, and a principal reason for including it here is to provide some knowledge of why the design exists as it does, and why some aspects can and some cannot be changed. Many of the other plans on the market make a selling‐point out of stating that they can be widely modified to suit individual needs. While this sounds attractive in principle, there are serious problems with this approach. The primary one is that changing the size of the machine can have serious negative consequences on its performance. Increasing a dimension can increase internal forces on machine components, as well as increasing the deflection of components. These stresses and strains can be many times in excess of the what would be encountered in the machine as it exists in these plans.

The assembly steps in these plans start with the fabrication of the wood components and finish with the metal ones. This sequence was chosen because it presents a smooth, seamless order of constructing the machine.

In short, you should not make changes to these plans unless you fully understand what the consequences might be. The sizes of all components have been optimized for the overall size and use of the machine. Proceed to make changes with extreme caution and at your own risk.

However, it is highly suggested to read through the entire set of plans and then decide if this sequence makes the most sense for you. If there is any doubt about the skills involved to construct the machine, then it is suggested to fabricate the metal components before the wood components. This sequence provides a couple of advantages: The first is that even though it may be more unfamiliar to many builders, metal can actually be easier to work. It has no perceptible grain and is therefore predictable in its behavior. Most of the metal parts are aluminum, which is a soft metal and has relatively low cutting forces involved, much like those of a hard wood. The second reason is that fabricating the metal parts will constitute the bulk of fabrication time and require the most patience to maintain build tolerances. The number of cuts, holes to drill and tap, and amount of hand filing and finishing will ultimately end up being a considerable amount of tedious time consuming work. This sequence will also quickly reveal the level of skills and stamina to complete the metal components. By the time all of the metal components are fabricated, the wood fabrication will most likely seem quick and easy.

MomusDesign

Assembly steps


Can changes be made to the plans?


design alterations and construction

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a. b. c. d.

Study existing designs that have been built by others. Construct something that looks similar. Be disappointed with some aspect of its performance. (Hopefully) build a second one.

Design can be a very complicated process, requiring not only significant knowledge but good decision making skills to balance the often conflicting criteria that are needing to be met. Progress in any field is typically incremental, with the breaking of revolutionary ground being the exception rather than the rule. Therefore, steps “a” and 'b” are both inevitable and desirable. The question becomes what knowledge and skills are necessary to successfully critique and improve upon existing designs? Design Process and principles The following is a brief attempt at explaining the thought process and rationale behind this particular machine design. This is provided for two reasons. First, to perhaps provide a general starting point and advice for those who decide to design their own machine. Secondly, to provide a foundation for those who may wish to make modifications to these plans. What follows is a list of points of understanding that were accumulated during the process of designing this machine. They range from observations of typical problem areas, to design philosophy, to structural formulas and engineering information. To those with engineering knowledge, please excuse any over‐simplifications of concepts. This information is aimed at those with little design expertise and is not intended to transform anyone into a capable engineer or designer. Rather, it is intended to illustrate how complex it can be to design a seemingly simple device and how quickly one can get in over their head, even when equipped with a little bit of over‐simplified information. Design hubris should be kept in‐check, in favor of the cautious and proven path.

Woodworking skills This may seem somewhat tangential to a design process, but it is not. Many builders of a CNC router, who are intending to use it to mill wood, possess very rudimentary woodworking skills. Many have never experienced trying to control a hand‐held router. It is important to have an intuitive understanding of the behavior of the material that will ultimately be milled with the CNC machine, and how it interacts with a cutting tool. A CNC router is a very advanced piece of woodworking equipment, and success in using it is going to be much greater if the operator has a solid understanding of woodworking basics and a feel for the material. Improving one's woodworking skills will quickly reveal important understandings of grain, how the tool wants to follow it, in which directions it wants to tear, and why it is important to control machine backlash some way other than through electronic compensation. The forces required to move a blade through wood, or to hold it back, may be unexpected, especially when it is spinning at 25,000 rpm in a router. Better woodworking skills will equate to a better feel for how to electronically control a cutting tool, and will also improve the build quality when constructing the actual machine. Use the router to build the machine If constructing a CNC router, then obviously at some point a router will need to be purchased for use as the spindle. By acquiring it early in the process, it can be used to fabricate the machine itself. Many of the wood parts for this machine can just as easily be cut with a router as they can a circular saw or a table saw. Several of the cutting operations, such as pockets, will actually require a router. With a guide‐fence and clamps, very accurate cuts can be achieved with the hand‐held router. Using the router while building the machine will quickly reveal the differences between moving the tool left or right along an edge (climb‐cutting vs. conventional cutting), the importance of feedrates and spindle speeds, how to plunge into a workpiece, the effect of different types of cutting bits, and the general forces involved.

design process


The design of a home‐built machine often has a design process that follows these steps:

MomusDesign

Designing a machine:


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Stiffness comes from a combination of properties. The first is the flexibility of the material itself, due to a property called Modulus of Elasticity. The second factor is how that material is arranged in space, due to a property called Moment of Inertia (or more correctly, the Second Moment of Area.) Thus the first factor is based on material properties, and the second on geometrical properties. Because stiffness comes from a combination of these two factors, it means that to some extent having a surplus of one property can make up for a deficiency in the other.

Joints Connections between components are as important as material choice. There is a huge difference in the amount of force that can be transmitted through different types of joints. One big limitation in using wood for any structural application, whether a machine, a building, or a piece of furniture, is designing adequate joint details. Subtle differences in how pieces come together can have a significant effect on strength. Creating strong joints in a material such as MDF is no small undertaking, but it can be done. Basic structural design principles Some understanding of very basic structural principles will go a long way in designing a machine. A few simple experiments can help illustrate them. Attempting to twist a cardboard box with no top is relatively easy. Taping a top in place so that all six sides are solid planes makes it many times more resistant to being twisted. This has increased the torsional strength of the assembly. Attempting to flex a ruler that is lying flat and spanning between two supports is also relatively easy. Repeating this with the ruler standing on its edge shows no perceptible deflection. This has increased the bending strength of the member. Attempting to hold a piece of thin paper straight out, while holding at only one edge, and it will droop down. Putting a 90 degree crease, or a curve, in the paper that is perpendicular to the edge being held, and it will now rigidly cantilever out. This change in geometry has made it into a form‐ resistant structure.

MomusDesign

A lack of stiffness causes several problems. The obvious one is that if the machine deflects under a cutting load, then the tool isn’t in the spot that the computer thinks it is. In other words, your cut is not going to be accurate. The other big problem is “chatter.” A machine is a dynamic structure, meaning there is motion involved. That motion can cause vibrations and oscillations in the machine components if it can flex excessively. At best, experiencing chatter may mean reducing cutting speed or taking cuts that are not as heavy. At its worst it can destroy the cutting tool, the part being cut, or even cause damage to the machine.

What this means is that even a very flexible material can be arranged to produce a strong and rigid structure. This is why a machine built of MDF has to be so bulky, as it needs to position the material in a way that can overcome its inherent flexibility. Unfortunately this is still not as good as using an inherently stiff material in a geometrically efficient way. So yes, a somewhat rigid machine can be built out of wood. No, never as rigid as cast iron, nor as compact.


Stiffness One of the biggest shortcoming of many home‐built machine designs is a lack of stiffness, or rigidity. Stiffness is the ability to resist deflection. Materials have “elastic” behavior. At its simplest, pushing on them causes them to deflect. Release the force and they spring back. Push too hard and it doesn’t spring back. When this happens, it has bent or broken, due to either exceeding the material's elastic limit and causing “plastic deformation,” or going beyond its yield point. ALL machines have some amount of deflection. A machine built of HDPE plastic has a very large quantity of it that may be easily seen by the naked eye. One built of MDF still probably has a considerable amount, and is often more than should be acceptable for construction of a machine. A machine that is built of massive cast iron and costs hundreds of thousands of dollars still has some deflection, it is just infinitesimally small relative to its cutting accuracy.


design process

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18

Here is a basic list of aspects that should have somewhat closely matched accuracy levels: ‐Frame material. ‐Rigidity of frame design (NOT the same as frame material) ‐Ability to align and adjust the machine. ‐Type of bearings or guides. ‐Method of driving motion. ‐Backlash, or the amount of play in the machine. ‐Electronic resolution of steppers or servos. ‐Machine speed. ‐Spindle power.

A model built as just described can be pushed, twisted, and flexed to see where the design lacks stiffness. If it seems excessively flexible, making modifications to the physical model, or constructing a new version, can be a quick way of making significant advances in improving the design. This method will often reveal areas of weakness that were not anticipated, and this will be happening during a phase where they are easily corrected. Once an actual machine is constructed, making structural changes may be nearly impossible. Attempting to push a physical model to the point of breaking can also be instructive. If it takes significant force, and feels like it does not flex at all before catastrophically exploding, it is a good indicator of the overall stiffness of the assembly. If it softly crumples, or easily comes apart at the seams, more design work is probably required. It is possible to build a posterboard model that is nearly impossible to break in your hands.

MomusDesign

Before dedicating significant time to constructing a CNC machine, it can be very valuable to evaluate the design by constructing a small‐scale physical model. In addition to revealing potential problems with overall constructability or interference of parts, it can give a sense of its structural performance. By building it out of a material that has some inherent flexibility, it will be easy to witness how the geometry of the design effects the stiffness. Materials such as 1/16” chipboard (material that cereal boxes are made from, can be sourced at a good art supply store,) mat board, posterboard, or bristol board are excellent for this purpose. Avoid stiff materials like foam core. The more flexible the material, the easier to see an exaggeration of where the design will flex. A model does not need to be constructed so that parts slide or move, it can be fixed in mid travel. However, it should be constructed in a manner that mimics how the material will really come together at joints, as this can be a significant location of flex.

Matched level of components A common problem with DIY machine design is the necessity of specifying individual components that work well in conjunction with each other. A machine should have a consistent level of accuracy, or rather of inaccuracy, in its components throughout. A scenario like installing expensive high accuracy ball screws for motion control on an MDF machine will never realize the benefit of the high quality components. The amount of flex in the MDF material, or its dimensional instability due to moisture in the atmosphere, will far exceed the tolerances that the ball screws can attain. The levels of accuracy between the two components may be off by orders or magnitude. The quality level of all components needs to improve together in order to see improvements in overall accuracy of the system, otherwise money is merely being wasted.


Building a model It is common to build a virtual 3d model of a potential design, with software such as SketchUp, Rhino3d, Solidworks, etc. However, one of the big problems that comes with the easy availability of 3d modeling software is that it does not give any sense of materiality and real‐world behavior. Every design works perfectly on the computer screen. The result being that endless variations of a design are drawn without a real understanding of its basic shortcomings, and few improvements are made from one iteration to the next.


design process

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Degrees of constraint One common problem in many DIY designs is having the machine bind under a cutting load. Each axis of the machine needs to smoothly roll on a bearing system, and each axis needs to have bearings configured in a way that will constrain the motion so that it will only go exactly in the direction of that axis. This typically requires many bearings that are spread somewhat far apart. All works well with this arrangement until forces on the machine cause flexing, and some components are no longer in exact alignment with the direction of travel, causing binding. The arrangement of bearings on the Y axis of the design in this manual are somewhat unconventional. They are arranged so that the right side of the gantry is fully constrained against rotation in two directions. The gantry in effect is then cantilevered out from this set of bearings. The bearings on the left side of the gantry act as outriggers that stabilize its position. The bearing configuration on the left is not fully constrained in itself, but provide constraint to the overall system in the third direction of rotation.

Alignment. Aligning a typical home‐built machine can be problematic. Smooth bind‐free operation requires accurate alignment between bearing surfaces on each axis. It requires getting the machine parallel, square, and in‐plane. This can be a very difficult task to accomplish. Nearly all home‐built machines provide some means of providing adjustability, however, many use methods that make fine adjustment very difficult or impossible. Some do not provide enough directions of adjustability. The biggest problem is that nearly none of them provide any sort of reference plane to measure from. It does no good if the machine can theoretically be aligned, but there is no practical way of making measurements to find that alignment. This design attempts to solve these problems in several ways. Using the manufactured faces of stock metal pieces provides some amount of automatic alignment between parts. All of the bearings have a set screw to allow very fine adjustments of their pre‐load against the axis rails that they ride along. Finally, by pouring a thin self‐leveling layer of a very low viscosity epoxy on the bed of the machine, it can be used as a consistent reference plane from which to base all alignments.

design process

MomusDesign

‐The machine flexing: frame, motor mounts, etc. ‐Play: space between bearings and rails. ‐Linear motion inaccuracy: rails not straight, variation in dimension, not parallel or in‐plane. ‐Linear drive inaccuracy. ‐Electronics error.

Removing one direction of constraint from the left is intentional. It has been done this way so that the machine cannot bind if there is excessive flexing of the gantry. Flexing of the gantry will allow a small rotation in one direction to absorb this force. While under these conditions there may be some inaccuracy in the cut due to deflection of the gantry, the machine will keep moving and not bind. Accepting this very minor inaccuracy was felt to be a better situation than having the machine bind, which most likely would result in a completely unusable part. When a machine with stepper motors binds, what can often happen is that the computer keeps feeding the signal to the motors because it does not know that there is a problem. If the machine suddenly starts to move again, it is now receiving code that is out of sync with where in the cutting process it left off. The result is a large cutting error. Do not add additional bearings to the left side of the machine unless you understand the implications for doing so. It will require much more accurate alignment of the machine to prevent binding.


Tolerance and accumulation of error Beyond creating a rigid machine that will not deflect under a load, there are other factors in design. One is the issue of tolerance. Many home‐built machine designs make claims like: “cuts accurate to .000025". A number like this is merely a theoretical electronic resolution of the stepper motors, and has no bearing on actual accuracy of the overall machine. It in no way translates to accuracy at the tip of the tool, which is where it counts. What does effect accuracy is the individual tolerances of the various parts of the machine working together. Sometimes inaccuracies will serendipitously cancel each other out, as an inaccuracy in one direction will be counteracted by an inaccuracy in the other direction, the net result being that the error is not large. But this is an uncommon situation, and the individual errors are more likely to accumulate and add to each other. So a theoretical accuracy tolerance for the machine is best arrived at by adding all of the possible causes of inaccuracy to arrive at a total possible inaccuracy number. Here are a few things that contribute:


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Structural design

Rubber Low density polyethylene HDPE Polypropylene Nylon MDF (wood composite) Oak wood (along grain) Pine wood (along grain) Magnesium metal (Mg) Aluminium alloy Brass and bronze Titanium (Ti) Copper (Cu) Wrought iron and steel

1,500‐15,000 30,000 200,000 217,000‐290,000 290,000‐580,000 530,000 1,600,000 1,300,000 6,500,000 10,000,000 17,000,000 15,000,000‐17,500,000 16,000,000‐19,000,000 30,000,000

Looking at this chart, the inherent problems of using materials like plastic or MDF for machine construction become immediately apparent. They are orders of magnitude more flexible than even the lowest modulus metals. The philosophy in the design of this machine was to use materials of high modulus wherever possible. One counter‐intuitive outcome of this is that it is often actually less expensive to use small quantities of higher modulus materials than large quantities of low modulus materials. Designing using higher modulus materials also allows the machine to be more compact, which can further help in reducing flex. It is important to understand that the ability for a material to resist deflection is not exactly the same as its “strength.” These are two separate measures of material properties. For our purposes, the ability to resist deflection is what is more important. If there is enough material to provide a stiff enough design, there is very little chance of it not being “strong” enough, so we can ignore that structural need.

MomusDesign

As mentioned earlier, there are two factors at play to achieve stiffness. One is a property called modulus of elasticity. This a property of the material and is essentially a measure of its flexibility. A higher number indicates a stiffer material. A stiffer material is obviously desirable when building a machine. The second factor at play is moment of inertia. This is a measure of stiffness of a shape or geometrical arrangement of the material in space. The same amount of a material can be used with differing amounts of efficiency. An example was given earlier of the bending efficiency of a ruler, comparing it when supported on its flat side vs. when on its thin edge. This phenomenon is happening due to the moment of inertia of the ruler being greater in one direction than the other. Another example would be to flex a thin steel rod. A steel rod that is about 1/4" in diameter can easily be flexed and bent by hand. However, that same quantity of material can be made into a large diameter hollow tube with a thin wall thickness. This tube would not be able to be flexed by hand. Both have the same amount of material, but the tube has a much higher moment of inertia.

To get an idea of the range of material stiffness, here is a modulus of elasticity chart. All values are in psi:


Rigidity: For the design of the machine in these plans, rigidity became the primary design factor, as everything springs from the stiffness of the machine. Accuracy goes hand in hand with flexibility. It does not matter if your electronics can control motion to .0001" if your machine frame flexes 1/8" under a cutting load. This seemed to be the biggest downfall of the existing home‐built designs. Many machines were being built primarily of MDF (medium density fiberboard.) This material is by nature very flexible. The manner in which it was being arranged often did not help the situation.


structural design

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‐Section dimensions. Increasing its size in section will make it stiffer. A 1" x 1" bar will be stiffer than a ½" x ½" bar. ‐Section shape. Making the bar taller will make a much bigger difference in making it stiff than will making it wider. (Think back to the ruler example). Another good example of this is a floor joist. A 2x12 floor joist is going to be stiffer than a 2x6 floor joist. ‐Length. A longer piece is going to be more flexible than a short one. ‐End constraints. The bar in this example is just resting on a support at each end. This means it can rotate slightly as the bar deflects. If the bar was held rigidly at each end, like if it was welded solidly to another object, it would make it more resistant to flexing. ‐Load. A load that is spread out over the length of a member will cause less flexing than if it is all concentrated at the mid‐point.

The calculation of deflection is a three step process:

MomusDesign

To find solutions to these questions, two types of information are required. First is the modulus of elasticity, which is a property of the material. The second is the moment of inertia which is a property of the cross sectional shape of the part. This information works in combination with other factors such as the overall length of the part, how a load is applied, and how its ends are supported.

Example: A simple piece of metal bar stock that has each end resting on a support. A single load is pressing down in the center of it. What factors make it flexible or stiff?


Moment of Inertia As briefly discussed on the previous page, the second factor in achieving stiffness is how the material is distributed in space. This is called moment of inertia, or more correctly, the second moment of area. As also mentioned, since most designs are driven by stiffness requirements rather than strength needs (the concept here is that if you built it so that it is stiff enough, it is going to automatically be strong enough) the focus here will be on stiffness. Unfortunately, comparing the moment of inertia of even very basic design options against each other requires some math. A few simple equations will be introduced here. Hopefully this will provide some (relatively) easy information to see the implications of alternate design decisions. These formulas will help compare scenarios such as increasing the dimensions of member, comparing solid shapes to hollow sections, and how much deflection increases if a span is increased.

1. Look up the material's modulus of elasticity in a chart. 2. Calculate the section modulus based on cross section shape. 3. Calculate the deflection. The deflection formulas take many of the factors such as end constraints and loading conditions into account, so it is just a matter of finding the formula that matches the situation.

structural design


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2

E=

Calculate moment of inertia

I=

cross sectional shape

30,000 200,000 217,000‐290,000 290,000‐580,000 530,000 1,600,000 1,300,000 6,500,000 10,000,000 17,000,000 15,000,000‐17,500,000 16,000,000‐19,000,000 30,000,000 30,000,000

max. deflection =

formula

W 4

a I = 12

a

=

W L3 48 E I

=

W L3 192 E I

=

W L3 3EI

L

a

simply supported at both ends, force applied at center of span.

3 bd I = 12

d

b 4 a I = 12

a

W

a

b 4

a

b

I = a12 b

4

L

fixed support at both ends, force applied at center of span.

a h

k

d

3 3 I = bd 12 hk

MomusDesign

LDPE HDPE Polypropylene Nylon MDF Oak wood Pine wood Magnesium Aluminium Brass & bronze Titanium Copper Wrought iron Steel

3

Calculate deflection


1

Find modulus of elasticity

b

W

I = 0.049 d

d

4

L

version 2.1 Units: All dimensions on this page are in inches.

D

d

4

4

I = 0.049 (D d )

fixed support at one end, force applied end of cantilever.

copyright 2013

Modulus of Elasticity units are in lb/in 2

structural design formulas

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23

Aluminum E=10,000,000

1.0

0.5

0.5

1.0

4

-simply supported at ends -force applied at center 1/2" square aluminum W= 10 lb at center L= 24" long

2

step

=

4

a I = 12

a I = 12

4 0.5 I = 12

4 1.0 I = 12

I = 0.00520833

I = 0.0833

W

W

L

L

W L3 48 E I

= (10) 24

138,240

3

step

W L3 48 E I

3

= (48) (10,000,000) (0.00520833)

MomusDesign

1

step

Now, lets change the material to 1" square aluminum. All else stays the same.


Example:

(10) 24

3

= (48) (10,000,000) (0.0833) 138,240

= 2,499,998

= 39,994,000

deflection = 0.055"

deflection = 0.003"

Note that the original example had over 17 times as much deflection as the second!

deflection example


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structural design conclusion

Among those other factors, it is unusual, indeed difficult, for any part to be designed so that there is only one type of stress involved. A good example of this would be a truss, which operates on the principle that its members are either in pure compression or pure tension. In practice this is very difficult to achieve and there is nearly always some amount of bending force introduced due to the realities of joint design. In the case of a CNC machine such as this one, the gantry experiences a combination of torsion and deflection forces. Not only do the cutting forces push on it causing it to deflect, but those forces are not aligned directly with its centerline. The cutting forces are cantilevered some distance down the Z axis. This eccentric loading introduces a torsional twist into the gantry.

A successful design also depends on creating joints that can transmit loads between parts in an effective and appropriate way. This is one other aspect that these simple calculations do not consider. Also keep in mind that all of this information pertains to static conditions. Remember that a machine tool is a dynamic condition and makes it much more complex to predict its structural behavior. Kinetic movements and rotating parts can introduce momentum, vibrations, and oscillations that can amplify static stresses to the point of breaking failure. Discussion of dynamic behavior is well beyond the scope of this set manual. As stated earlier, the intent of providing this information is twofold. First, it is here to illustrate that what may seem simple can be quite complex to calculate and predict. Please bear that in mind when tempted to make changes to the plans. The second reason for providing this knowledge is that it can give at least some sense of the implications of making changes. It is quite easy to do a few calculations and see that doubling the length of part makes it much more flexible. To directly see those numbers and be able to compare them may just aid in your judgment of how far dimensions can deviate from those in the plans before the cross sectional size of a member needs to change. In the ideal situation, this knowledge might help you improve upon the design as given

MomusDesign

Not only do cross section properties complicate the calculations, but there are complexities even within what may seem to be an adequate solution according to these calculations. For example, increasing the size of a hollow section while reducing its wall thickness will result in a stiffer member. However, there are limits to this. Wall thickness can not be reduced too far or the member will be vulnerable to buckling under a load. So while the basic deflections calculations show it to be adequate, there are other factors that may reject this as a solution.

Understanding and calculating combinations of forces can be very complex and is well beyond the average home‐builder's analytical abilities. It is important to keep in mind that this is nearly always the rule rather than the exception, so the structural calculations shown here should be viewed as a guideline for understanding some very basic principles. It can be used as a rough means of comparing the effects of changing sizes of members. This should in no way be seen as a definitive guide for structural design, if anything it should be taken as an illustration of just how difficult it can be to understand even simple loads on a part.


These calculations on the previous pages are adequate for very basic cross sectional shapes and simple loading situations. Essentially they are for finding deflection in simple types of beams. Unfortunately, the real world is rarely that cooperative. As soon as the cross section becomes more complex (like an I‐beam for example,) or multiple pieces are attached together (like the gantry on this design,) calculations become much more complicated. Determining the deflection in these composite assemblies is beyond the scope of this simple demonstration. Similarly, any introduction of loads other than the very idealized conditions shown in the formula diagrams also makes calculation tremendously more complicated and is beyond our scope.


structural design conclusion

page

25

GENERAL NOTES ‐ Do not measure off of printed drawings. Use dimensions as indiacted on drawings. Scale is not indicated on drawings due to variation in printer accuracy. Printing at 100% scale factor may not guarantee exactly 100% on paper!

Z

‐Do not make changes to the design without having a full understanding of their implications. This machine was carefully designed such that all components work together as a integrated whole. Changes may have unforeseen implications later in the build process, or may negatively affect the operation of the finished machine.

X

Y

rear

left

right

front

‐Counterbores. Many metal parts indicate counterbores. These are OPTIONAL. Counterbores are present to reduce the thickness of material to be tapped, to make hand tapping easier. ‐Filing to fit. If tolerances are not held accurately enough it may be necessary to file some parts slightly during assembly. ‐BE SAFE. Use good judgment while working and do not attempt anything that is beyond your ability or that may jeopardize your personal safety.

MomusDesign

‐Tolerances. An accuracy of +/‐ 1/32" is generally sufficient on metal parts. Any exceptions to this will be noted. Cut wood parts should aim for this same level of precision.

Naming conventions for axes and directions follow these standards throughout:


‐Dimensions on mechanical parts are given in Imperial decimal units. Dimensions are given to either 2 decimal place accuracy or may be given as full decimal equivalents to fractions. This does not indicate degree of tolerance required.


general build notes

page

26

METAL

6063‐T52 rectangular tube

STEEL

(2) @ 24.00"

A36 hot rolled angle

48.00” total

.25" x 2.50" CRS bar (1) @ 12.00” (1) @ 22.50”

6061‐T6 square bar

36.00” total

1.25" x 1.25" x .125" angle (2) @ 24.00"

(1) @ 24.00"

24.00” total

.75" x .75" bar

.25" x 1.50" CRS bar 1018 cold rolled rectangular bar

1.50" x 3.00" x .125" wall

48.00” total

(2) @ .75” (2) @ 1.25 (1) @ 2.50” (1) @ 6.75” (1) @ 7.25” (4) @ 7.375” (1) @ 8.50” (1) @ 10.75” (1) @ 20.75”

96.00” total

.125" x .75" bar (1) @ 5.625”

6.00” total

.1875" x 2.50" bar

.1875" x 3.00" bar (2) @ 24.00"

48.00” total

.375" x 1.25" bar Within each size of stock, individual part lengths are also listed. These quantities can be used if ordering material by individual part length. If ordering by individual part length, note that most suppliers will only guarantee cut accuracy to +/‐ 1/16", and cuts may not be perfectly square or have high finish quality.

6061‐T6 rectangular bar

(1) @ .75” (1) @ 1.00” (1) @ 1.25” (1) @ 1.875” (1) @ 2.50”

8.00” total

.75" x 1.00" bar

NOTE: Before ordering metal or other parts, consult the ADDENDUM on page 171 of this manual. It outlines upgrading the machine with thrust bearings on the Z axis (HIGHLY RECOMMENDED.) A separate bill of materials is listed for these parts in the addendum.

(4) @ 1.75” (2) @ 2.75” (1) @ 5.625” (1) @ 11.25”

MomusDesign

9.00” total


(1) @ 4.25” (misc) 4.5"

ALUMINUM

NOTE: Total quantity for each size of stock is listed. Total quantities typically include additional material length to include width of saw cuts. These quantities can be used when ordering material in bulk lengths. If ordering in bulk lengths, note that it is often less expensive to round quantities up to the nearest whole foot.

31.00” total

.75" x 1.25" bar (1) @ 2.00" (2) @ 2.25” (1) @ 6.75” (2) @ 4.25"

22.50” total


.75" x 1.75" bar (2) @ 4.25

9.00” total

bill of materials 1

page

27

(2) 4' x 8' sheets, 3/4" sanded finish plywood, such as “cabinet grade.” Note on plywood: While "cabinet grade" is specified, the important qualities to look for in plywood is that it has a sanded finish on both faces, preferably a high count of core plies, and core plies with no voids. Nominal 3/4" plywood is often marked and measures 23/32". This thickness, or close equivalent metric sizes, will not affect the construction of the machine base. To the greatest extend possible, the design allows for such small variation in material thickness.

PLASTIC

socket head cap screws (2) #10‐32 x .75” (7) 1/4‐20 x 1/2” (1) 5/16‐18 x 2.5” (4) 5/16‐18 x 3” soc. head cap screws (OR machine screws) (4) #4‐40 x 1” (8) #10‐32 x 1” (4) #10‐32 x 2.5"

hex head bolts (1) #10‐32 x .75” (or 5mm x 20mm) (14) 1/4‐20 x .5” bolts (modified, see page 86) (28) 5/16‐18 x 1.5” (8 modified, see page 86) (1) 5/16‐18 x 2.5” lag bolts (30) 1/4” x 1.25”

ELECTRONICS

nylon insert lock nut

Stepper motor choice may depend on the type of materials that you intend to cut with the machine. For very soft materials, such as foam, the machine may perform adequately with stepper motors with a lower rating than the suggested 275 oz./in. Stepper motors, motor drive, and power supply must all be carefully matched to each other for proper motor performance. Information on making these decisions is beyond the scope of this manual. For this reason, it is suggested that motors, drive(s), and power supply be purchased as a prepackaged kit from a reputable source.

HARDWARE grade 8 hardware (4) (8) (4) (4)

5/16‐18 x 3” bolts 5/16 washers 5/16 lock washers 5/16‐18 hex nuts

wood screws (1 lb. box) #10 x 1.25" (1 lb. box) # 10 x 3" nails (1 lb) 6d bright finish

(46) sealed roller bearings, ABEC‐7 skate 8mm x 22mm x 7mm (608 size) (2) 10 tooth timing pulleys, 3/8" wide, .200 XL pitch, bore dia. to match stepper motor shafts 400XL timing belt‐ 200 teeth x 3/8" width, McMaster part # 6484K445 500XL timing belt‐ 250 teeth x 3/8" width, McMaster part # 6484K451 OR 10 feet 3/8" wide x .200 XL pitch open ended timing belting.

soc. head cap screws (OR hex bolts) (1) 1/4‐20 x 1” (1) 5/16‐18 x 2”

(1) 24"' x 24"' sheet, polycarbonate. ~1/8" min. thickness, ~3/16" preferred.

Min. recommended stepper motor size: 275 oz./in.

MOTION

(4) (8) (48) (35)

#4‐40 #10‐32 1/4‐20 5/16‐18

flat washers (SAE) (4) #4 (20) #10 (100) 1/4” (100) 5/16 (6) 3/8" (modified, see page 86) lock washers (4) #4 (12) #10 (28) 1/4” fender washers (2) 5/16 set screws (grub screws) (50) #10‐32 x 3/8" (2) #10‐32 x 3/4" roll pins (4) 3/16" x 2" threaded rod (allthread) (96") 1/4‐20 (total length)

8" 3/8‐10 acme one‐start precision rod, McMaster part # 99030A327 (36" length) (1) delrin anti‐backlash nut w/ .925" square flange, DumpsterCNC part # AC38101‐LN (1) delrin shaft coupler, @stepper shaft dia., DumpsterCNC part # AC38101‐AC OR 8" 3/8‐8 acme two‐start precision rod, McMaster part # 99030A315 (36" length) (1) delrin anti‐backlash nut w/ .925" square flange, DumpsterCNC part # AC38082‐LN (1) delrin shaft coupler, @stepper shaft dia., DumpsterCNC part # AC38082‐AC OR 8" 3/8‐8 acme four start precision rod, McMaster part # 99030A303 (36" length) (1) delrin anti‐backlash nut w/ .925" square flange, DumpsterCNC part # AC38084‐LN (1) delrin shaft coupler, @ stepper shaft dia., DumpsterCNC part # AC38084‐AC Acme rod choice is a compromise between speed and resolution. Single‐start will have a finer resolution, but slow travel speed. Four‐start will move quickly with slightly less resolution. In general, the two or four‐start will still have enough resolution for most needs, and is thus recommended (four‐start preferred). Also, low torque stepper motors (below 300 oz/in) may require single start or double start, for additional mechanical advantage.

ELECTRICAL (12') stepper motor wire, cont. flex, shielded, McMaster part # 7673K44. Limit switch wire. (5) limit switches, SPDT submini lever switch, Radio Shack part # 275‐016 (or similar). Emergency stop switch.

MomusDesign

PLYWOOD

HARDWARE


NOTE: Consult ADDENDUM (page 171) for additional Z axis thrust bearing parts that are not listed in this bill of materials.

MISC. wood filler. carpenters wood glue. paint and primer. 24 fluid oz. (32 fluid oz. recommended) low viscosity epoxy resin & hardener, <600 cps viscosity. 30" piano hinge. (2) 1 1/2" utitlity hinges. (2) 2" utility hinges. (2) magnetic door latches. cable ties.

bill of materials 2


page

28

ROUTER

# reqd. 1 2 2 2 5 1 3 6 1 1 1 1 1 1 1 1 1 1

S T U V W

1 1 2 2 1

cover front cover top cover side cover side filler cover rear

FABRICATED PLASTIC PARTS part # part name P1 cover window front P2 cover window top P3 cover window side

MODIFIED HARDWARE part # part name H1 thin head bolt H2 shortened bolt W1 enlarged washer

# reqd. 8 14 6

STUD SCHEDULE (1/4‐20 studs) part # length # reqd. SA 1.25" 5 SB 1.5" 1 SC 1.75" 12 SD 2.25" 2 SE 2.5" 2 SF 2.75" 3 SG 3.25" 4 SH 3.50" 2 SI 8.00" 1

ROUTER STUDS (1/4‐20 studs) part # length # reqd. RSA 2.75" 4 RSB 3.00" 4

Model Ridgid R2401 Bosch Colt

# reqd. 1 1 2

MomusDesign

FABRICATED WOODEN PARTS part # part name A bottom skin B Y rib 1 C Y rib 2 D X rib 1 E X rib 2 F top skin G wall plate H vertical rib I right wall plate J right top plate K left top plate L left skin M rear plate N rear plate door O left inner skin P right inner skin Q right skin R front plate


BASE ASSEMBLY COVER

FABRICATED METAL PARTS part # part name # reqd. 01 gantry bottom 2 02 gantry tube 1 03 gantry left top 1 04 gantry right top 1 05 gantry spacer 1 06 gantry outer right 1 07 Y motor mount front 1 08 Y motor mount rear 1 09 X belt plate 1 10 X belt clamp 1 11 Y rail 1 12 carriage block rear upper 1 13 carriage block rear lower 1 14 bearing block 3 15 bearing block tapped 1 16 carriage block front right 1 17 carriage block front left 1 18 spacer upper 2 19 spacer lower 2 20 Z motor mount right 1 21 Z motor mount left 1 22 Z cable plate 1 23 Y belt clamp 1 24 Z rail 1 25 Z rail block 1 26 nut plate block 1 27 nut plate 1 28 X rail 2 29 X rail angle left 1 30 X rail angle right 1 31 X plate right 1 32 X plate left 1 33 X belt pulley adjuster 1 34 cable arm 1 1 35 cable arm 2 1 36 cable arm mounting block 1 37 router mount Ridgid R2401 2 38 router clamp Ridgid R2401 2 39 router mount Bosch Colt top 1 40 router mount Bosch Colt bott. 1 41 router clamp Bosch Colt top 1 42 router clamp Bosch Colt bott. 1 43 X limit switch bracket 2 44 Y limit switch bracket 2 45 Z limit switch bracket 1

COVER

X RAILS

Z AXIS

CARRIAGE

GANTRY

LIST OF FABRICATED PARTS


NOTE: Consult ADDENDUM (page 171) for additional fabricated parts that are not listed here. (for addition of Z axis thrust bearing)

Fabricated Parts list

page

29

08 Y motor mount rear

stud SD (2.25") 1/4‐20 x 1" bolt

07 Y motor mount front

stud SA (1.25") (7) 1/4‐20 x .5" socket head cap screws. 10 X belt clamp 5/16‐18 x 2.5" bolt.

09 X belt plate 06 gantry outer right 05 gantry spacer 04 gantry right top

03 gantry left top


01 gantry bottom

MomusDesign

stud SC (1.75")

11 Y rail 02 gantry tube

stud SG (3.25") stud SH (3.50")

01 gantry bottom


stud SG (3.25")

exploded gantry

page

30

stud SA (1.25") stud SC (1.75") 23 Y belt clamp

stud SG (3.25")

15 bearing block tapped 12 carriage block rear upper

22 Z cable plate

stud SE (2.50")

13 carriage block rear lower

20 Z motor mount right

19 spacer lower stud SC (1.75") 14 bearing block 14 bearing block stud SC (1.75")


16 carriage block front right 18 spacer upper

MomusDesign

21 Z motor mount left

(4) 5/16‐18 x 3" grade 8 bolts. 17 carriage block front left


14 bearing block stud SC (1.75")

exploded carriage

page

31

Locations of all bearings indicated in red. Look closely, some are obscured by other parts. There are a total of 38 bearings in this illustration, including the two that are used as a belt pulley.


MomusDesign

All bearings are sealed ABEC‐7 skate bearings, 8mm x 22mm x 7mm.


bearing locations

page

32

24 Z rail 25 Z rail block

stud SB (1.50")

stud SF (2.75") stud SH (3.50")

39 router mount BOSCH top

stud SA (1.25")

BOSCH COLT

40 router mount BOSCH bottom 41 router clamp BOSCH top

stud SC (1.75")

42 router clamp BOSCH bottom

RIDGID R2401


27 nut plate

MomusDesign

26 nut plate block

stud RSB (3.00")

37 router mount RIDGID


38 router clamp RIDGID

stud RSA (2.75")

exploded Z axis

page

33

33 X belt pulley adjuster 30 X rail angle right 28 X rail

5/16‐18 x 2.00" bolt. #10‐32 x .75" hex head machine screw. (or 5mm x .8)

29 X rail angle left

5/16‐18 x 2.5" socket head cap screw.


MomusDesign

28 X rail

31 X plate right 32 X plate left


exploded X rails

page

34

stud SF (2.75")

stud SI (8.00) shorten as required for cable management.

washer W1

34 cable arm 1


MomusDesign

36 cable arm mounting block

washer W1 stud SF (2.75")

35 cable arm 2 washer W1


exploded cable arms

page

35

J right top plate K left top plate

H vertical rib I right wall plate

G wall plate

H vertical rib

G wall plate H vertical rib G wall plate

D X rib 1 E X rib 2 D X rib 1

B Y rib 1


F top skin

MomusDesign

H vertical rib

C Y rib 2 B Y rib 1

version 2.1 A bottom skin

exploded base inner structure

copyright 2013

page

36

N rear plate door

electronics bay door (not in Bill of Materials)

M rear plate Q right skin L left skin

R front plate

Inner assembly. See page 36 for exploded view.

MomusDesign

P right inner skin


O left inner skin


exploded base skins

page

37

T cover top

U cover side S cover front

MomusDesign

V cover side filler


W cover rear

U cover side V cover side filler


Base assembly. See page 37 for exploded view.

exploded cover

page

38

material: 6061‐T6 alum. stock size: .75 x .75

# required:

2

7.375 14.75

.375

3.125 6.25

.375 0.75

.375 0.75

.75 1.5

.3125 DIA., 2 holes. #10‐32 threaded, 2 holes (from bottom side).

MomusDesign

4.25


2.125 0.75

.375

.375 0.75

0.75

.75

.75

1.5

1.5

.375

.375

0.75

version 2.1

0.75

copyright 2013

.375 DIA., 2 holes.

part #

1 gantry bottom

page

1

39

material: 6063‐T52 alum. 24.00 48

2.25 4.5

3.25

3.25

6.5

6.5

3.25 6.5

3.25

3.25

6.5

6.5

stock size: 1.5 x 3.0 x .125

3.25 6.5

.75 1.5

# required:

1

.50 DIA., 7 holes. .375

0.75

0.75

2.125

2.125

4.25

4.25

.875 .4375

.375 DIA., cut & file to slots. .3125 DIA., 4 holes, cut & file to slots.

1.75

0.875

3.00

2.25

.75

6

4.5

1.5

3.25

3.25

6.5

6.5

.4375 0.875

3.25 6.5

3.25

3.25

6.5

6.5

3.25 6.5

1.50 3


.375

25.5

0.75

MomusDesign

.3125 DIA. 12.75

.375

.3125 DIA., 7 holes. .4375 0.875

.4375 0.875

2.125

2.125

4.25

4.25


12.75 .3125 DIA., 4 holes, cut & file to slots. 25.5

.375 .3125 DIA.

part #

0.75

2 gantry tube

page

2

40

material: 6061‐T6 alum. stock size: .75 x .75 #10‐32 threaded, 2 holes. 1/4‐20 threaded, CBORE .375 DIA x .25 DP., 2 holes.

# required:

1

7.375 3.125 6.25

.375

.375

0.75

0.75

.375 0.75

.75 1.5

.375 DIA.

4.00 8


2.125

MomusDesign

14.75

4.25

.375 0.75

.75 1.5

version 2.1 .375

copyright 2013

.375

0.75

0.75

part #

.375 DIA., 2 holes.

3 gantry left top

page

3

41

#10‐32 threaded, 2 holes. .375 DIA., 2 holes.

material: 6061‐T6 alum.

1/4‐20 threaded, CBORE .375 DIA x .25 DP., 2 holes.

stock size: .75 x .75

7.375 14.75

2.125

# required:

3.125

4.25

6.25

1.25

1

1.25

2.5

2.5

.375

.375 .375 0.75

.75 1.5

2.00

1.00

4

2

.375 0.75

.75 1.5

.375

MomusDesign

0.75


0.75

.375

0.75

0.75

1.25

1.25

2.5

2.5

3.75

1.875

7.5

1/4‐20 threaded, CBORE .375 DIA x .25 DP., 2 holes.

3.75

version 2.1

.25 DIA., 2 holes.

copyright 2013

#10‐32 threaded, 2 holes. part #

.375 DIA., 2 holes.

4 gantry right top

page

4

42


# required:

5.625 11.25

3.75

1.00

7.5

2.00 4

2

1.00 2

MomusDesign

1.75


.875

1

.375 0.75

.75 1.5

.25 DIA, 2 holes. .3125 DIA, 2 holes. .125 0.25

version 2.1 Note that this part is not symmetrical. Holes are closer to one end.

5 gantry spacer

copyright 2013

part #

page

5

43


.3125 DIA, 2 holes. File/drill to slots. 5.625

stock size: .75 x 1.00

11.25

.375

.375

0.75

0.75

.375

.375

0.75

# required:

0.75

1

1.00 2


MomusDesign

.375 0.75

.25

2.00

0.5

2.00

4

4

.375 DIA., 2 holes.

#10‐32 threaded, 2 holes (from rear side). .3125 DIA., 2 holes

.75

2.625

1.5

5.25

4

.375 0.75

.75 1.5

2.00 4

3.75

1.00

7.5

2


1/4‐20 threaded, CBORE .375 x .50 DP, 2 holes.

part #

#10‐32 threaded, 2 holes.

6 gantry outer right

page

6

44

1/4‐20 threaded, CBORE .3125 x .75 DP.


.1875 0.394


1.856 3.712

.303 0.606

# required: 1.5

1


.375

MomusDesign

.75

#10‐32 threaded, CBORE .25 DIA. x .875 DP., 2 holes. (CBORE from bottom).

0.75

.625 1.25

2.25 4.5

.125R

1.25 2.5

.75 1.5

.375 0.75


part #

7 Y motor mount front

page

7

45

material: 6061‐T6 alum. 1/4‐20 threaded, CBORE .3125 x .75 DP. stock size: .75 x 1.25

.625 1.25

.375 0.75

# required:

1

1.5

.75 .303


1.856

MomusDesign

0.606

3.712

.1875 0.394

#10‐32 threaded, CBORE .25 DIA. x .875 DP., 2 holes. (CBORE from bottom).

2.25 4.5

1.25

.125R .75

2.5

1.5

.375 0.75


part #

8 Y motor mount rear

page

8

46

.20 0.8

.063 0.25

.094


0.375

enlarged belt groove detail .


45° # required:

.062 0.125

.375

.25 0.5

.75 1.5

.3125 DIA., 2 holes. .3125 DIA.

.875

1 ea.

0.75

MomusDesign

0.75


.375

1.00

1.75

2

1.875 3.75

.625 1.25

.625 1.25

.625 1.25

1.25 2.5

.625 1.25

1/4‐20 threaded.

1.25 2.5

PART # 9

version 2.1

PART # 10

copyright 2013

part #s

9 X belt plate & 10 X belt clamp

page

9,10

47

material: 1018 cold rolled steel stock size: .25 x .2.50


22.50 45

3.25 6.5

3.25 6.5

3.25 6.5

3.25 6.5

3.25 6.5

3.25 6.5

1

MomusDesign

# required:

1.50 3

1.25 2.5

2.50 5

1/4 ‐ 20 threaded, 7 holes. .25 0.5


part #

11 Y rail

page

11

48

#10‐32 threaded, 2 holes. .375 DIA., 2 holes. NOTE: These two holes are NOT centered in the material thickness.


1/4‐20 threaded, CBORE .375 DIA x .25 DP, 2 holes. (CBORE from bottom).


6.75 .875 13.5

2.9375

1.75

# required:

5.875

.875

.875

1.75

.375

1

1.75

.375

0.75

0.75

0.5

.393 0.813

.375 0.75

0.75

.375 .75 1.5

.375 DIA., 2 holes. #10‐32 threaded, 2 holes (back side). .375 DIA., 2 holes.

.375

MomusDesign

.25

0.813


.393

.375

0.75

0.75

.75 1.5

.375

.375

0.75

0.75

.875

version 2.1

.875

1.75

1.75

3.375 6.75

copyright 2013

1.6875 3.375

part #

12 carriage block rear upper

page

12

49

#10‐32 threaded, 2 holes (from bottom). .375 DIA., 2 holes. NOTE: these two holes are NOT centered in the material thickness. 1/4‐20 threaded, CBORE .375 DIA x .75 DP, 2 holes. material: 6061‐T6 alum.

6.75 .875 13.5

2.9375

1.75

5.875

.875

.875

1.75

1.75

.375


.375

0.75

0.75

.393

.25

0.813

.393

0.5

0.813

.375 0.75

# required:

0.75

.375

1

.75

1.688

6.75

.875 1.75

3.375

.188

0.375 0.375

.375

0.375 0.375

.875 1.75

0.75

.375 0.75

.625 1.25

.75 1.5

.438 0.875

.75 1.5

.438 0.875

.375

.375

0.75

0.75

.438

1.25 2.5


.375 DIA., 2 holes. #10‐32 threaded, 2 holes (from back side). 3.375 .188

MomusDesign

1.5

.438

0.875

0.875

.50

.50

1

1

.125 R (Typ.)

.1875 DIA., 4 holes.

R 0.25

1.313 2.625

4.125 8.25

.375 DIA., 2 holes. 1.313 2.625

ALTERNATIVE DESIGN: Rather than cut notches at the version 2.1 corners of the part, leave copyright 2013 rectangular. Add counterbores and (2) additional #10‐32 threaded holes as indicated. Requires use of longer part # bolts (2") at two bearing locations .

13

13 carriage block rear lower

page

50

.375 DIA.

.25 0.5

material: 6061‐T6 alum. stock size: .75 x 1.00 .25 0.5

2

.75


1.00

1.5

.25

.25

0.5

0.5

.1875 0.375

.4375 0.875

1.75 3.5

.875 1.75


1.375 2.75

3

MomusDesign

# required:

#10‐32 threaded, CBORE .25 DIA x .25 DP, 2 holes.


part #

14 bearing block

page

14

51

.375 DIA.

.25 0.5

material: 6061‐T6 alum. stock size: .75 x 1.00

0.5

.25

2

.75 1.5

.25

.25

0.5

0.5

.1875 0.375

.4375 0.875

.6875 1.375

1.75

.875 1.75


3.5

#10‐32 threaded, CBORE .25 DIA x .25 DP, 2 holes.

.6875


1.00

1

MomusDesign

# required:

1.375

1/4‐20 threaded.


part #

15 bearing block tapped

page

15

52

material: 6061‐T6 alum. #10‐32 threaded, 2 holes (bottom side).

1/4‐20 threaded, CBORE .375 DIA. x .25 DP., 2 holes.

.375 DIA., 2 holes.


8.50 17

0.5

13

5.625

1

.375 0.75

.75 1.5

.25 0.5

3.438

.875

6.875

1.75

1.938


3.625

3.875

1

.50

11.25

7.25

.375 0.75

MomusDesign

.8125 1.625


0.75

# required:

.25

6.50

.375

.75 1.5

.8125

5.625

1.625

11.25

.375

6.50

0.75

13

version 2.1

.375 DIA., 2 holes.

copyright 2013

#10‐32 threaded, 2 holes. part #

.375 DIA., 2 holes.

16 carriage block front right

page

16

53

material: 6061‐T6 alum. #10‐32 threaded, 2 holes.

1/4‐20 threaded, CBORE .375 DIA. x .25 DP., 2 holes. (CBORE from bottom).

.375 DIA., 2 holes.


7.25 14.5

6.50

.375 0.75

# required:

13

.8125

1

5.625

.375 0.75

.75 1.5

.25 0.5

.875

3.438 6.875

1.75

1.938

3.625

3.875

7.25

.375 0.75

MomusDesign

11.25


1.625

.75 1.5

.8125

5.625

1.625

11.25

.375

6.50

0.75

13


.375 DIA., 2 holes. #10‐32 threaded, 2 holes.

part #

.375 DIA., 2 holes.

17 carriage block front left

page

17

54

material: 6061‐T6 alum. stock size: .75 x .75 .75 1.5

# required:

.375 0.75

2

.375


MomusDesign

0.75

.75 1.5

.375 DIA.

.75 1.5

NOTE: Use stock thickness as this dimension to maintain consistency between pieces.


part #

18 spacer upper

page

18

55


.75 1.5

.375 0.75

# required:

2

.625


MomusDesign

1.25

1.25 2.5

.375 DIA.

.75 1.5


part #

19 spacer lower

page

19

56


.197 0.394

2.75 5.326

1.856

.197

3.538

0.394

# required:

1

.75


.625 R

MomusDesign

1.5

.375

R 1.25

0.75

.25 DIA., 2 holes. EQUAL 1.856

EQUAL 1.682

1.125 2.076


1.00 .50 2

.25 0.5

1

.375 0.75


part #

20 Z motor mount right

page

20

57

2.75 5.5

1.125


2.25

EQUAL

EQUAL

1.856

.375

1.856


0.75

.25 DIA., 2 holes.

.625 R R 1.25

# required: .75

1

0.394

3.712

.197 0.394

1/4‐20 threaded, CBORE .375 DIA. x .25 DP., 2 holes.

.75 1.5

.25 0.5

1.00 .50 2

.25 0.5

1.00

.50

1

1

.375

2


.197

1.856

MomusDesign

1.5

.25 0.5

0.75

#10‐32 threaded, .75 deep, 2 holes.


part #

21 Z motor mount left

page

21

58

material: 6061‐T6 alum. 4.25 8.5

1.125 2.25

.50

.928

1

1.50 DIA.

.928

1.856


.25 DIA., 4 holes

1.856

# required:

1

1.5

MomusDesign

1.125


.75

2.25

.928 1.856

1.50 3

2.25 4.5

.928 1.856

.125R R 0.25

.3125 DIA.

2.25 4.5

.1875 0.375


NOTE: Cut from 2.50" wide plate stock, as it is a more common stock size than 2.25"

22 Z cable plate

part #

page

22

59

.20 0.8


.063 0.25

stock size: .375 x 1.25 .094 0.375

enlarged belt groove detail .


.375 0.75

1.25 2.5

.625

1.25

.25 0.5

.125 R.

1

MomusDesign

# required:

.75 1.5

.3125 DIA.


part #

23 Y belt clamp

page

23

60

material: 1018 cold rolled steel stock size: .25 x 2.50

# required: 12.00 24

.375 0.75

6.125 12.25

MomusDesign

.875 1.75

1.25


2.25 4.5

1

2.5

1.25 2.5

2.50 5

1/4‐20 threaded, 5 holes. .25 0.5


part #

24 Z rail

page

24

61


.375

22.5

2.25 4.5

.875 1.75


11.25

0.75

6.125 12.25

1.25

1

MomusDesign

# required:

2.5

.50 1

1.00 2


.75 1.5


part #

25 Z rail block

page

25

62


1.25

# required:


.75

2.5

1.5

MomusDesign

.375


0.75

.875 1.75

4

2.00

.375 0.75

.625 1.25

1

.25 0.5


1/4‐20 threaded, 2 holes. part #

26 nut plate block

page

26

63

material: 6061‐T6 alum. stock size: .375 x 1.25 2.50 5

# required:

.75 1.5


.375

1

0.75

.338 0.675

MomusDesign

.125 DIA., 4 holes. .50 DIA.

1.35

R 0.25


.675 .125 R

.625 1.25

1.25 2.5

.675 .9375 1.35

.4375 0.875

1.875

.487 0.973

.4375 0.875

.338 0.675

.375 0.75

NOTE: Hole pattern is for DumpsterCNC anti‐ backlash nut. Modification may be necessary if using a an anti‐backlash nut from another manufacturer.

27 nut plate


part #

page

27

64

material: 1018 cold rolled steel stock size: .25 x 1.50


24.00 48

.75 1.5

3.75 7.5

3.75 7.5

3.75 7.5

3.75 7.5

3.75 7.5

3.75 7.5

2

MomusDesign

# required:

.75 1.5

1.50 3

1/4 ‐ 20 threaded, 7 holes. .25 0.5


part #

28 X rail

page

28

65

material: A‐36 hot rolled steel stock size: 1.25 x 1.25 x .125

1.5

3.75 7.5

3.75 7.5

3.75 7.5

3.75 7.5

3.75 7.5

3.75 7.5

.75 1.5



.125

Grind/file 1/16" off of top edge.

0.246

.75 1.5


24.00 48

.75

1

MomusDesign

# required:

1.25 2.5

.125 0.251

1.25 2.5


part #

29 X rail angle left

page

29

66

material: A‐36 hot rolled steel stock size: 1.25 x 1.25 x .125

# required:

0.607

1.5

.625 1.251


.928

.928 1.856

1.856

2.75 5.5

Grind/file 1/16" off of top edge. 24.00 48

1.5

.125 0.251

3.75 7.5

3.75 7.5

3.75 7.5

3.75 7.5

3.75 7.5

3.75 7.5

.75 1.5

.125

1.25 2.5



.30

.75

MomusDesign

.75R


.75

1

0.246

1.25 2.5


part #

30 X rail angle right

page

30

67


# required:

1

.75

MomusDesign

1.5


24.00 48

3.75

.375 DIA. .3125 DIA.

3.75

7.5

7.5

3.75 7.5

3.75 7.5

3.75

3.75

7.5

7.5

1.856

.928

1.856

.928

3.00 6

1.75 3.5

1.50 2.996

.5625 1.125

2.25 .375 3.875 4.5

2.732

.3125 DIA., 14 holes.


0.75

7.75

1.375

1.50 DIA.

.928 1.856

.928 2.75 1.856

5.5

.1875 0.375


part #

31 X plate right

page

31

68


# required:

1

.75

MomusDesign

1.5


24.00 48

3.75 7.5

3.75 7.5

3.75 7.5

3.75 7.5

3.75 7.5

3.75 7.5

.5625 1.125

1.75 3.00 3.5

6

.3125 DIA., 14 holes.

.1875 0.375


part #

32 X plate left

page

32

69


# required:


.75 1.5

.375 0.75

.50 1

1.25 2.5

.375 0.75

1

MomusDesign

.3125 DIA.

#10‐32 threaded.

.375 0.75

.156 0.312


part #

33 X belt pulley adjuster

page

33

70

.375 DIA., 25 holes, .75 center to center. NOTE: these are lightening holes and are optional. material: 6061‐T6 alum.

20.75 20.00 41.5

.375

40

0.75

.75


1.5

.3125 DIA., 2 holes (at ends).

Radius both ends.

PART # 34

.375 DIA., 12 holes, .75 center to center. NOTE: these are lightening holes and are optional. 10.75 10.00 21.5

20

.375

1 ea.


1.5

MomusDesign

# required:

.75

0.75

.75 1.5

.3125 DIA., 2 holes (at ends). .75 1.5

PART # 35


part #s

34 & 35 cable arms

page

34,35

71

material: 6061‐T6 alum. stock size: .75 x .75 2.50 5

.375 0.75


.75 1.5

.25 0.5

.3125 DIA.

.375 0.75

.75 1.5

.375 0.75

1

MomusDesign

# required:

1.00 2



part #

36 cable arm mounting block

page

36

72

1/4 ‐ 20 threaded, .3125 CBORE to leave .50" thread length.

.3125 DIA.

1/4 ‐20 threaded.

.375 0.75

.75 1.5

material: 6061‐T6 alum. for: RIDGID R2401

3.625 7.25

.3125


.3125

0.625

0.625

# required:

2

4.25 8.5

2.125


1.00

MomusDesign

4.25

.688

2

1.375

.50 1

30°

.375 0.75

30°

.094R R 0.188

.062 R R 0.125

.25 R R 0.5

1.75 3.5

1.00 2.054

45°

45° .563 1.125

.375

.1875 0.375

0.75

1.3125 R R 2.625

1.21 R R 2.419


part #

37 router mount Ridgid R2401

page

37

73

material: 6061‐T6 alum. 1.3125 R R 2.625

.4375

1.21 R R 2.419

0.875

for: RIDGID R2401

.375


0.75

45°

45°

.75

# required:

.75

1.5

1.5

2

1.25 2.5

.062 R


MomusDesign

R 0.125

.125R R 0.25

.875 1.75

2.50 5

.875 1.75

4.25 8.5


.375 0.75

.75 1.5

3.625 7.25

.3125 0.625

.3125 0.625


part #

38 router clamp Ridgid R2401

page

38

74


.3125 DIA.

1/4 ‐20 threaded.

.375 0.75

.75 1.5


3.625

for: BOSCH COLT

7.25

.3125

.3125

0.625

0.625


# required:

4.25 8.5

1

2.125 4.25

1.00

.688


MomusDesign

1.375

2

.50 1

30°

30° .375 0.75

.094R R 0.188

.25 R R 0.5

1.75 3.5

.062 R R 0.125

1.00 2.054

60°

.4375 0.875

.563

60°

1.125

.375 0.75


part #

39 router mount Bosch Colt top

page

39

75


.3125 DIA.

1/4 ‐20 threaded.

.375 0.75

.75 1.5

material: 6061‐T6 alum. for: BOSCH COLT

3.625 7.25

.3125

.3125

0.625


0.625

# required:

4.25 8.5

1

2.125 4.25

1.00

.688

MomusDesign

1.375

2


.50 1

30°

30° .375 0.75

.094R R 0.188

.25 R R 0.5

.062 R

1.75

R 0.125

3.5

1.00 2.054

45°

45°

.563 1.125

.375 0.75

.4375 0.875

1.50 R

1.388 R R 2.776


part #

40 router mount Bosch Colt bottom

page

40

76

material: 6061‐T6 alum. for: BOSCH COLT .6875 1.375

1.50 R

1.388 R

R3

R 2.776

.375


# required:

0.75

.75

1

.75

1.5

1.5

1.25


.062 R

MomusDesign

2.5

R 0.125

.875 1.75

2.50 5

R 0.25

.125 R

.875 1.75

4.25 8.5


.375 0.75

.75 1.5

3.625 7.25

.3125 0.625

.3125 0.625


part #

41 router clamp Bosch Colt top

page

41

77

material: 6061‐T6 alum. 1.50 R

for: BOSCH COLT

1.388 R

R3

R 2.776

.6875 1.375

.375 0.75

45°


45° # required:

.75

1

.75

1.5

1.5

1.25


R 0.125

MomusDesign

2.5

.062 R R 0.25

.125 R

.875 1.75

2.50 5

.875 1.75

4.25 8.5


.375 0.75

.75 1.5

3.625 7.25

.3125 0.625

.3125 0.625


part #

42 router clamp Bosch Colt bottom

page

42

78

1.375 2.75

.188 0.375

.75 1.5

.093R

.375

.125R

R 0.188

0.75

R 0.27

.125R

.375

R 0.25

0.75

.125

.125 dia., 2 holes.

0.25

1.25 .625 2.5

1.375 2.75

1.25

.625

.125 dia., 2 holes.

1.25

.375 .75 0.75

1.5

.313 0.625

.25 0.5

.25

.188 0.375

0.5

.125R

.188

.313

1.25

.188

0.375

0.625

.625


0.375

1.25 2.5

# required: as indicated


.625

MomusDesign

PART # 44 Y limit switch bracket (2) required

PART # 43 X limit switch bracket (2) required

1.25

.125R R 0.25

.063R R 0.125

.625 1.00 1.25

.75 .375 1.5

.125 dia., 2 holes.

2

0.75

.188 0.375

.625 1.125

1.00 2

.25 0.5

PART # 45 Z limit switch bracket (1) required

NOTE: All brackets are dimensioned for Radio Shack switch, part #275‐016. Use of other switches may require modification of bracket design. NOTE: Stock size is listed as .1875 x 2.50, as these can be cut from the remaining material that is specified for part #22 (Z cable plate.)

43, 44, 45 limit switch brackets


page

79

PLYWOOD LAYOUT NOTES: These are suggested layout of parts on 4' x 8' plywood sheets.

(H) vertical rib

(H) vertical rib

(B) Y rib 1

(M) rear plate

(B) Y rib 1 (H) vertical rib (H) vertical rib

(L) left skin

(C) Y rib 2

(H) vertical rib (H) vertical rib

(C) Y rib 2 (P) right inner skin

(J) right top plate

4' x 8' sheet, 3/4" finish sanded plywood, such as "cabinet grade."

(I) right wall plate (G) wall plate (W) cover rear (G) wall plate (S) cover front

(G) wall plate (R) front plate (E) X rib 2 (E) X rib 2

MomusDesign

(O) left inner skin


(K) left top plate

(D) X rib 1

Dashed lines indicate cuts to be made later.

(D) X rib 1

(A) bottom skin

(E) X rib 2

(Q) right skin

(F) top skin

(E) X rib 2

Allow for width of saw cuts.

(N) rear plate door

(E) X rib 2 (T) cover top

(U) cover side

(U) cover side

version 2.1

(V) cover side filler

copyright 2013 (V) cover side filler

plywood sheet layouts

page

80

31.00 31

31.00 31

3.00

3.00

3

3

.75 0.75

.75 0.75

(A) bottom skin

material: finish sanded plywood

(F) top skin 26.00

26.00

26

26

(1) Required

(1) Required

stock size: 3/4" thickness

# required:

0.75

0.75

3.00

3.00

3

31.00

3

23.00

31

23

2.50

2.50

2.5

2.5

(B) Y rib 1

(D) X rib 1

X 2

(2) Required

(2) Required


.75

.75

MomusDesign

as indicated

NOTE: All slots 3/4" nominal width, centered on dimension centerlines. Adjust actual slot width for light press fit with measured thickness of rib material. 29.50

23.00

29.5

23

1.875

1.875

1.875

1.875

6.50 6.5

6.375 6.375

6.375 6.375

6.50 6.5

8.25 8.25

1.25 1.25

7.375 7.375

2.50 2.5


(C) Y rib 2 (2) Required

(E) X rib 2 2.50 2.5

(5) Required

1.25 1.25

plywood parts A‐F

page

81

26.00

24.50 24.5

26

.75 1.5

3.00

(G) wall plate

3

(3) Required (L) left skin 14.00 14

(1) Required 8.50

NOTE: Cut opening for passthrough of wires in one rib. It does not need to be this exact size and shape.

8.5

(H) vertical rib

3.00 3

45°


A

Section A‐A

(6) Required


A # required: as indicated

24.50

31.00

24.5

1.688 1.688

31

2.75 2.75

2.625

3.00

2.625

3.00

3

3

25.00

2.438

3.00

(i) right wall plate

3

4.00 4

(M) rear plate 1.50 1.498

(1) Required

.188 0.188

(1) Required

1.50 DIA.

13.25 13.25

6.75 6.75

25.25 25.25

2.438 2.438

2.75 2.75

2.625 2.625

2.50 2.5

2.50 2.447

3.00

(j) right top plate 1.50 1.498

3

(1) Required


2.50

MomusDesign

25

26.50 26.5

.188 0.179

1.50 DIA. 25.25

(N) rear plate door

25.25

8.25 8.25

(1) Required (K) left top plate

version 2.1

3.00

copyright 2013

3

(1) Required

plywood parts G‐N

page

82

26.00

26.00

26

26

.75

2.00

0.75

3.00

6.625

3

2

2.00

2.00

2

10.00

A

6.625

2

10.00

10

10

4.00 4

A 10.00 10

(O) left inner skin

6.50 6.5

14.00 14

(1) Required (Q) right skin A


4.75 4.75

(1) Required


26.00 26

0.75

4.00

6.625

# required:

A

3.00

6.625

3

as indicated

4

A 10.00 10

(P) right inner skin

3.00 3

25.00 25

3.00 3

(1) Required

10.75 10.75

1.00 2

2.00 4

1.00

13.25

2

13.25

(R) front plate 45°

4.00

MomusDesign

A


.75

2.50 2.5

(1) Required

8

31.00 31

version 2.1 .75

Section A‐A

copyright 2013

pocket routed 5/8" deep

1.5

Typical pocket, enlarged detail. plywood parts O‐R

page

83

NOTE: All dashed lines indicate cuts to be made later in the assembly sequence.

32.50 32.5

.75 1.5

45°

Section A‐A A A

27.00 27

A

A material: finish sanded plywood

T cover top

A

(1) Required 26.75 26.75

A


# required:

22.25 22.25

(1) Required

32.50 32.5

1.5 R

1.5 R

R 1.5

R 1.5

W cover rear (1) Required

26.00 26

13.00 13


S cover front

MomusDesign

as indicated

U cover side 11.50 11.5

(2) Required

11.50 11.5


V cover side filler

3.00 3

(2) Required

plywood parts S‐W

page

84

PLASTIC LAYOUT NOTES: 20.00

Below is a suggested layout of parts on 24" X 24" polycarbonate sheet.

20

Leave space for width of saw cuts.

2.00 R, typ. R2

material: polycarbonate sheet

P1 cover window front

P3

16.00 16

(1) Required

stock size: .125" min. thickness

P1

# required: as indicated

24

P2 2.00 R, typ. R2

P2 cover window top 8.00 8

(1) Required

24" x 24" polycarbonate sheet.


24.00

MomusDesign

P3

4.00 4

.75 R, typ. R 0.75

P3 cover window side 7.75 7.75

(2) Required


2.00 2

cover plastic

page

85

3/32" 0.223

file/grind head of bolt to leave approximately 3/32" thickness remaining.

5/8" 1.173

5/16 x 1 1/2" bolt

washer to fit 5/16 bolt. Outside diameters of washers may vary. Make sure outer diameter is larger than the outside diameter of the 22mm bearings. If it is not, use a washer with a larger outside diameter.

1/4‐20 x 1/2"bolt shorten bolt to approx. 3/8" thread length. These attach the X rails to the rail angles, and may need to be tested and adjusted for exact length required.

washer W1 (6) modified washers required


(8) modified bolts required

MomusDesign

file inside diameter to approximately 5/8"


(14) modified bolts required

modified hardware

page

86

NOTE: Mark all red lines onto panels with a pencil as indicated. See assembly directions for more detailed description of these marked lines.

T cover top

equal

12.00

equal

6.25

12

6.25

1.50 1.5

2.25 2.25

3.5

MomusDesign

equal

3.5


equal

Measure as indicated in drawings, and use previously cut plastic windows as templates to trace. Trace lines tightly to window.

S cover front

11.6 11.595

1.50 1.5

for rear plate for y rib 1

U cover side 2.50 2.5

.75 0.75

29.50 centered on panel length 29.5

5.00 4.975

11.6 11.595

23.00 centered on panel width 23

1.50

A bottom skin

1.5

U cover side

for x rib 1

version 2.1

for x rib 1

.75

2.50 2.5

copyright 2013

0.75

5.00

for y rib 1 for front plate

4.975

panel markups

page

87

WOOD FABRICATION All of the wood parts can be fabricated with relatively simple woodworking equipment. All of the basic cutting can be accomplished with a circular saw, such as the one pictured to the right. When combined with a straightedge fence which can be clamped to the sheet material, it will be capable of just about all cutting needs in this project. A table saw would be useful for cutting repetitive parts of the same width, such as the inner ribs, to make it easier to keep their dimensions consistent. However, with careful fence setup, these components can also be cut with a circular saw.


MomusDesign

The few cuts that can't easily be done with a circular saw or table saw can easily be done with a router. This project is designed to use a trim router, such as the one to the right, as the spindle. Purchasing the router at the beginning of the project will allow it to be used to cut small cutouts and pockets that are found on several of the components, as well as curved cuts. Router mount drawings are provided for two models, the Ridgid R2401 and the Bosch Colt. The mount design can be altered and adapted for most similarly sized trim router. The use of spiral up‐cut bits, rather than straight type bits, is suggested. These are similar in form to end mills used in a milling machine, but have flute angles and cutting angles that are specifically suited for wood. The increase in cutting performance over straight bits is well worth any additional cost.

Both the circular saw and the router can be used with a fence to increase their accuracy. Commercially produced fences with integral clamps are available. Alternatively, a straight, rigid length of metal can also be used. Pictured to the right is a length of 1" x 2"rectangular aluminum tubing and two C‐clamps to secure it in place. With careful setup, very accurate cuts can be accomplished.


Don't forget both hearing and eye protection. These are not optional!

wood fabrication

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88

A few simple layout tools are required. A good quality framing square, a triangle or machinist's square, tape measure, and a pencil. Make sure the square and triangle are actually at 90 degrees. It may seem obvious that the legs would be exactly perpendicular, but low quality versions can be very inaccurate. You can check accuracy by placing it along a known straight edge and striking a perpendicular mark. Flip the square or triangle 180 degrees and make another mark parallel to the first. If it is in square, the lines will be exactly parallel. If not, the lines will be closer together at one end or the other. Note that this test is only as accurate as the straightedge you are using.

When drilling holes in wood, a set of brad‐point drill bits is worth the investment. They cut a considerably cleaner hole than regular twist bits, which are intended primarily for metal.


MomusDesign

In addition to the tools shown, you will most likely need a few other traditional hand tools, such as a hand‐saw, wood chisels, hammer, a nail set, etc.. An electric sander will also be helpful in preparing the wood surfaces prior to painting.

Whatever selection of tools you end up using, what is most important is accuracy of layout and cutting. Be careful to make precise measurements and thin, crisp pencil marks. Cut to the waste side of the line, as seen in the photo to the right, to maintain the desired dimensions of the finished pieces. Okay, time to refer to the drawing sheets for the wood parts and start cutting! Cut all of the wood parts on pages 80‐84 to their overall sizes.


wood fabrication

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89

With all of the wood components cut to their overall sizes, there are several which have smaller specialty cuts. The inner skin panels each contain two pockets. These should be cut with the router, prior to cutting the 45 degree bevel along the edges of the panels. Mark the locations of the pockets and set the depth of cut to about 1/8" less than the thickness of the material. Rout the pockets to within 1/8" of the marked lines.


MomusDesign

After first removing material to within 1/8" of the marked lines, return for a finish pass that cuts right to the line.

The cuts shown to the right were done entirely by hand, but the fence can be used to increase the straightness of the cuts. Exact size and precision of these pockets is not required, as they are present only to provide wrench clearance while servicing the machine. After the pockets are routed, cut the 45 degree bevels on the top edges, as seen in the image to the left. This can be done either on a table saw, or with a circular saw and fence.


wood fabrication

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90

There round holes in several parts, such as the one marked in the image to the left. These cuts are best accomplished with a hole saw. Several of the metal components also have holes of the same size, so purchase of "bi‐metal" hole saws will allow cutting both materials. Two sizes of hole saws, 1 1/4" and 1 1/2”, will serve to cut all large round holes in the project.


MomusDesign

Drilling one or more holes tangent to the outside diameter of the final hole, as shown to the left, will provide space for chips to clear. This will make the sawing operation much easier. A hole at the center may also be pre‐drilled, to act as a pilot to align with the center drill that is integrated into the hole saw. Using the hole saw in a drill press at a low spindle speed is suggested, as well as using a piece of scrap wood as a backup board to avoid splinters on the back of the cut. The finished cut, and the plug that will need to be removed from the saw, should look like the image to the lower left.

As seen in the series of images to the right, several components have square holes in them. These can easily be accomplished by drilling a series of holes with the hole saw to remove a bulk of the material. The router can then be used to remove the remaining material.


wood fabrication

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91

Many of the internal rib components contain notches, which allow them to slide together with perpendicular ribs. To maintain consistency in location, these are best cut across all ribs of the same type in one operation. This can be accomplished with a circular saw as seen to the right. Clamp and mark the cuts on the ribs. Measure the thickness of the wood stock, and mark the cuts to correspond to this thickness. Correct slot width will result in a small amount of force being required to assemble the ribs.


MomusDesign

Set the sawblade depth dimension to just over one half of the rib width. Carefully make a cut to the inside of each of the marked lines.

Make a series of closely spaced cuts to remove the rest of the material from the slot, as shown to the right. These cuts can also be made on a tablesaw with a dado blade, or with a radial arm saw. The cuts could also be made with a hand saw, preferably in a miter box, and using a chisel to remove the waste material from the slot.


wood fabrication

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92

As shown in the series of images to the left, one rib requires a pass‐through to accommodate wiring for the electronics. Thus, its size is not crucial. The suggested size, indicated on the drawings, leaves adequate material to allow nailing into this piece. This cut can also be made by removing a bulk of the material with a hole saw, and finishing with the router.


MomusDesign

The image to the right shows all of the wood components for the base.

Cut the polycarbonate material for the cover windows, as shown in the image to the right. Leave the protective film attached to the plastic while making the cuts. If the polycarbonate being used is relatively thin, less than about 1/8", it may be carefully cut with a utility knife. It may also be cut with a circular saw and a standard fine‐tooth finish blade. Regardless of method, use the fence to clamp the plastic sheet to a scrap sheet of wood while making the cuts.


wood fabrication

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93

ASSEMBLY OF WOOD COMPONENTS On the bottom skin (part A), draw the pattern of lines that are shown in red in the diagram to the left. The lines are all spaced 3/4" apart. A more detailed drawing of these layout lines is shown on page 87. Slide the X and Y ribs together as shown in the middle left photo. Drill 3/16" clearance holes as shown in the left photos, and generously countersink.


MomusDesign

Place the assembled ribs onto the bottom skin as shown in the top right photo. The ends of the ribs should all fall along the drawn layout lines as shown. With a pencil, mark around each rib onto the bottom skin, as shown to the right.

Remove the rib assembly from the bottom skin. The penciled rib outlines will be used as guides for glue application.


wood base assembly

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94

As shown in the series of images to the left, apply carpenter's glue to the area where the ribs meet the lower skin. Reposition the ribs on the skin and attach with #10 x 3" wood screws. Use caution that the assembly does not shift as the screws are tightened. The wet glue can act as a lubricant and allow the pieces to slide easily. Also be sure that none of the screw heads are proud of the top faces of the ribs, as they will interfere with later placement of the top skin. As seen in the lower left image, apply glue to the front edges of the ribs and to the lower skin as shown. Position the two Y rib 1 (parts B) and clamp as shown to the right.


MomusDesign

With clamp pressure applied, secure the two Y rib 1 parts to the lower skin with the #10 x 3" wood screws. Once fully secured to the lower skin, attach with #6 finish nails into the endgrain of the X ribs, as indicated in the red circles to the right. Use a nail set if necessary, so that the heads are below the surface.

Using the same method and sequence of gluing, clamping, and nailing, attach the two X rib 1 parts as shown to the right. The base is now ready for attachment of the top skin.


wood base assembly

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95

As shown in the image to the left, position the top skin on the base. Offset the skin in each direction, and transfer the centerlines of the ribs to top of the skin with pencil lines. These lines will be used as a guide for fastening the top skin. Remove the top skin, apply carpenter's glue to the tops of all ribs, and carefully position the skin. Using the lines as guides, nail through the skin and into the ribs with #6 finish nails. The assembly should look like the lower left image.


MomusDesign

As shown in the upper right image, apply glue to the end Y rib. Spread it so that it evenly coats the surface. Position the front plate (part R), and secure with #6 finish nails into the rib. Then nail along the edges of the top and bottom skins into the front plate, as shown in the right image.

Install the rear plate (part M) in the same manner. The base assembly should now look like the image to the right.


wood base assembly

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96

As shown in the image to the right, assemble the vertical ribs (parts H) to the lower wall plates (parts G.) Attach with #6 finish nails and carpenter's glue. The center vertical rib is centered along the length of the wall plate. Prior to assembling, drill and countersink clearance holes for installation of #10 screws through the wall plates and outside vertical ribs as shown.


MomusDesign

Slide the assemblies down between the front and rear plates until they are in firm contact with the top skin of the base. Place a straightedge across the tops of the ribs as shown in the image to the right. If they are not all exactly the same height, either trim the ones that are taller or shim the shorter ones as necessary, so that their tops are parallel to the base. Measure up to the straightedge at several points to check this. Shims can be made of paper or thin paperboard if necessary. The tops of the ribs need to be exactly the same height so that the top plate will be flat when installed.

When the alignment of the vertical ribs is satisfactory, remove the assemblies from the base. Apply and spread glue to the mating surfaces, and reposition. Attach the lower wall plate to the base with #10 x 1 1/4" wood screws. With the lower plates securely fastened, secure the vertical ribs to the front and rear plates with the #10 x 1 1/4" screws.


wood base assembly

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97

Trial fit the top wall plates as shown in the image to the left. If the plywood material is thinner than the full 3/4" that is specified, the top of the plate may be slightly lower than the top edge of the front and/or rear plate, as seen to the left. If the top plate exhibits this condition, trim the front/rear plates as shown in the lower left image. Apply glue to the mating surfaces and install the top wall plates with #6 finish nails. (Not pictured) With the side walls in place, the inner and outer skins (parts L, O, Q, and P)can be fastened to the base assembly with 6d finish nails. Use the exploded view drawing on page 37 as a guide. The top edges of the outer skins should be flush with the top surfaces of the wall plates. The bottom edges of the inner skins should sit flush against the top skin.


MomusDesign

Position the X plates (parts #31 and 32) on to the top of their corresponding top wall plates (parts K and J.) Be sure that the correct ends of the X plates are facing forward. Align the rear edges of the components so that they are flush. With a pencil, trace the locations of the holes in the aluminum parts to the wood parts, as shown in the image to the right.

As shown to the right, drill a 1/8" pilot hole in the center of each hole location that was transferred. Between and around this first series of holes, drill another series of clearance holes for #10 wood screws. Countersink this second set of holes.


wood base assembly

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98

Apply and spread glue to the mating surfaces, and fasten the top plates (parts K and J) with #10 x 1 1/4” screws. The top plates are positioned exactly above the plates beneath them. The rear edge of the top plates should be flush with the rear surface of the rear plate. This should leave one thickness of plywood remaining at the front and sides of the machine, as seen in the image to the right.

MomusDesign

25.00" BENCHTOP CNC ROUTER PLANS

Measuring between the two top plates, as shown in the right image, the dimension should be 25.00", and be parallel from front to rear. If it is smaller than this dimension, the inside edge (s) of the top plates can be carefully trimmed with the router and a guide or fence. If the dimension measures slightly larger than 25" it can be left as it is.

The base is now complete, and should look like the image to the right. Sand any proud edges, set the nail heads below finish surfaces, and fill heads with wood filler. The base can now be primed and painted.


wood base assembly

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99

Mark the window locations on the corresponding plywood cover parts. Reference the drawing on page 87 for dimensions of these locations. Use the previously cut plastic window panels as templates, and trace around them as shown to the left. Draw a second series of lines, offset 3/8" to the inside of the window outlines, as shown to the right.


MomusDesign

Using the router, remove material to the inside of the two lines. A hole saw can be used to remove large quantities of material close to the line. These cuts can be done freehand if you are comfortable to do so with the router. As they are not critical for fit of other parts, any cutting error will only effect appearance.

Set the router cutting depth to 1/32" ‐ 1/16" greater than the thickness of the plastic window material. Rout this depth to the pencil outline of the windows, to provide a rabbet for the installation of the plastic. While routing, check the fit of the plastic in the depression often.


cover assembly

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100

When the rabbets have been cut for the installation of the plastic windows, assembly of the cover can begin. As seen in the image to the left, assemble the cover sides (parts U) to the filler pieces (parts V) with glue and nails. Attach one of the side assemblies to the cover top (part T) as seen to the right. While nailing together, be careful not to place nails close to the angled pencil lines that extend up the sides and across the top. A saw cut will later be made along this line. Keeping any nails at least 1.5” from this line will be a safe distance.


MomusDesign

Attach the cover front (part S) to the assembly. Measure and mark a centerline on the front and top parts, so that the front will be centered when it is installed. Use care to ensure that the top and side are as square as possible when attaching the cover front. As seen in the upper right photo, a carefully scribed pencil line can be used as a guide to help to maintain squareness. Glue and nail the cover front to the top along its edge. Attach the side filler to the front with screws from the rear. In the top right image, it can be seen that clearance holes for these screws have been pre‐drilled.

The rest of the cover assembly will use the machine base as a working support, to ensure that the cover fits as tightly as possible. Stand the left side assembly in position on the base, as seen in the image to the right.


cover assembly

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101

Place the assembled cover pieces onto the left side assembly, which is standing on the base, and fasten with glue, nails, and screws as were used on the right side. Check for correct alignment and squareness multiple times, before and during attachment. With the cover assembly still standing on the base, attach the rear panel (part W.) Attach it to the edges of the cover assembly, but do not attach it to the base at this time.

As seen to the right, carefully measure and clamp a fence to allow cutting along the angle marks on the side pieces with a circular saw. Set the blade depth as deep as possible, to cut partially into the cover top.


MomusDesign

With both side cuts made, reposition the fence to cut across the cover top. Setting the saw blade at a 30 degree tilt will allow it to align with the side cuts. Carefully position the fence so that the cuts will align at their ends. After cutting, the cover will now be in two pieces.

As seen to the upper left, mark and cut a shallow rabbet for the piano hinge, using the router. Corners of the rabbet may need to be cleaned out square with a wood chisel. Check the fit of the hinge as seen to the left. When the hinge is installed there should be a gap between the two cover pieces that is the thickness of the circular saw blade.


cover assembly

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102

Remove the cover from the base. The parts can now be sanded, finished, and painted. It can be helpful to plan where wiring will be run for the machine electronics before painting the base. As seen in the image to the right, two holes were cut with a hole saw for wiring to pass from the electronics compartment to the cable management arms. A hole was also cut into the rear plate door (part N) for the router cord. The door will be installed during a later stage.


MomusDesign

Place the two halves of the cover assembly on the base. With all of the edges of the cover sitting tightly to the base, there should be a gap between the two halves that is equal to the thickness of the circular saw blade.

While maintaining this consistent gap, install the piano hinge to the two cover halves. The assembly should look like the image to the left. With the two halves connected via the hinge, install the plastic windows. Apply a thin bead of silicone adhesive in the window rabbet. Spread it to an even thickness. Do not apply an excessive amount, as it will be pushed from the groove and onto the surface of the plastic window, which will be unsightly. Remove any protective film from the windows and carefully set the plastic into the adhesive. Press lightly to set. The installed windows should sit flush to the cover surfaces, as in the image to the right.


cover windows and hinge

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103

FABRICATING THE METAL PARTS: The most efficient method of fabricating the metal parts is to do each type of operation all at once. More in‐depth descriptions of each step are on the following pages. The following fabrication sequence was used here: 1. Cut all of the pieces to their overall lengths. If necessary, file the cut ends of the parts while holding them in a vise, to clean them up and make them as perpendicular as possible to the part. 2. Lay out all locations of holes and any secondary cuts with a marker and scribe.

Metal Fabrication Sequence

3. Center punch all of the holes. Use a spring loaded centerpunch for accuracy and speed.

1. Cut Lengths

4. Drill all holes. It may be quickest to drill all of each size hole at once. Keep the same size drill bit chucked in the drill press and drill all holes of that size in all of the parts before changing bits. It may be faster to clamp and unclamp parts in the drill press vice than to constantly change drill bit size while working on only one part at a time.

2. Hole Layout

5. Drill counterbores. Here it may be easiest to drill the primary hole, keep the part clamped, change the bit, and then drill the counterbore. This will maintain concentricity.

5. Counterbore

6. Tap all threaded holes.

6. Tap Holes

7. “Cut” the large and complex part shapes, such as the router mounts, by stitch drilling a series of closely spaced holes to nibble through the material. Use a hand file to finish the parts.

7. Plate Cuts 8. Studs

8. Fabricate the studs. Referencing the stud schedule on page 29, cut all of the steel studs to length from threaded rod. File the ends flat, with a chamfer around the edge. Threading a nut onto the rod before cutting can help straighten any thread deformation as it is removed. However, this method should be unnecessary if finish filing is done properly. Keep the finished studs organized by size.

9. Hardware

9. Fabricate the modified hardware. Referencing the drawings on page 86, modify the bolts and washers as indicated. These modifications can all be done with a hand file. Keep these finished parts organized as well.


4. Drill Holes

MomusDesign

3. Centerpunch Holes


metal parts fabrication sequence

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104

METAL FABRICATION Most vises have jaw faces that are serrated. Using these to clamp aluminum parts can badly mar the finish surface. The solution is to buy or fabricate a set of jaw covers. There are commercial versions available in many types of non‐ marring materials: brass, plastic, rubber, etc. The images to the right illustrate a set of covers that were quickly fabricated from a piece of common aluminum roofing flashing. Taking some measurements from the vise, transfer this information to a paper pattern. The covers should wrap part way around the jaws to hold themselves in place. It may take a couple of adjustments to arrive at a pattern that will fit well. A sheet of card stock/ cover stock, or other thick paper material will be durable as a pattern.


MomusDesign

Transfer the pattern to the aluminum sheet with a fine tipped marker. The aluminum can be cut by scoring with a utility knife blade and then lightly bending it back and forth. It will snap off cleanly along the score mark. The material is thin enough that curves and inside corners can be cut this way. Wrap the cover as tightly as possible around the vise jaws. It is OK if they are slightly loose. This type of aluminum is very thin, and will wear out after some use, so keep the pattern to make more covers in the future.

Another helpful clamping device is a block to hold round stock, such as threaded rod, in the vise. These were quickly fabricated out of two lengths of 3/4" square oak stock. They were clamped together with a strip of paper mat‐board between them as a spacer (cardboard or a thin strip of wood would work fine). Drill a series of holes in common sizes. These are very helpful when making studs from threaded rod. They work wonderfully to hold them without damaging the threads, such as while filing their ends flat, as in the photo to the left.


clamping tools

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105

The tools to the left were used to mark the locations of cuts on the lengths of material. These are a steel engineer's scale with 1/64" divisions, a felt tip marker, a carpenters awl, and a small square. To measure pieces longer than the 6" scale, a 24" carpenters square was used, hooked over the end of the material. The marker is used to provide a colored background to scribe through. A blue marker may work better than a black one, as it may provide better contrast when a line is scribed through it. Blue is also the color of the traditional machinist’s dye that is used for this operation. Mark the area where the cut is to be located with the felt tip marker. The scratch awl is used for just that‐ to scratch a thin, accurate line through the area of color. The scribed line should not go deep into the material, just enough to go through the marker. If the marker is washed off, the scribed line should just barely be visible, and barely be felt with a fingernail.


MomusDesign

Use the square to extend the scribed line all the way around the material. The end of the last line should meet up exactly with the first line. This will serve as a check that the marks are precisely perpendicular to the edges. With the piece clamped in the vise, begin cutting with a hacksaw. Note that the cut is just to the side of the scribed line. It just barely leaves the scribed line on the finished piece. Use the edge of your finger as a guide for the blade, and begin to cut carefully and slowly. Keep the blade horizontal and only apply pressure on the forward stroke. After cutting about 1/8"‐3/16" deep, remove the piece, rotate it 90 degrees and make another cut on this face, also about 1/8" ‐ 3/16" deep. Continue this all the way around the perimeter of the part, as seen to the lower left. Like the scribing, the last cut should exactly line up with where you began. With a consistent 1/8" ‐3/16" groove all the way around the part, make a final cut all the way through. The groove will help guide the blade straight through the material on the final cut. The completed cut should now be perpendicular to length of the material and require minimal clean‐up with a file.


scribing & cutting stock

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106

While perfectly adequate cuts can be made with a simple hacksaw, the method is tedious. The large number of parts on this machine can by cut much more quickly and accurately with a simple power miter saw, as shown in the image to the left. A common fine‐toothed carbide tipped blade designed for wood can be used, however, a much finer finish can be achieved with a blade designed specifically for use in aluminum. These blades have a negative cutting rake angle. The difference in cut quality between a wood blade and an aluminum blade can be seen in the image to the right. The part to the rear was cut with the aluminum blade.


MomusDesign

The blade used here is was made by Onsrud, and was purchased directly through the manufacturer via their ebay storefront. Best performance with this type of blade can be achieved with a blade lubricant, such as the wax stick in the image to the right. Carefully lower the spinning blade onto the wax stick prior to making a cut, to coat its teeth.

When making a cut, be sure that the work is securely clamped to the saw. Pull the saw trigger and allow the blade to come to full speed. The blade used here is quite heavy, and its quickly accelerating mass will move the saw significantly if it is not clamped securely to a surface. Gently lower the blade into and through the work piece. Release the trigger and allow the blade to come to a full stop BEFORE raising it back up through the cut part. This will greatly minimize the chance of kickback or having the blade catch an edge of the part.


ONLY use this method if you are comfortable with the equipment. Wear full safety gear and never place any part of your body directly in line with the spinning blade.

cutting stock with a miter saw

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107

The aluminum parts can all be cut either by hand or with a miter saw. It is recommended to cut the cut the steel parts to length with a hacksaw, or other cold method such as a metal cutting bandsaw with coolant. Do not use any method that will introduce significant heat, such as abrasive cutting blades, as heat may cause small warping of the material. Cut all of the aluminum and steel parts to length. To stay organized, as each part is cut to length write the dimension of its length on it with a marker. It is also helpful to write the part number or name.


MomusDesign

Keep the parts organized. There will be a lot of parts in total, so keep organized with some sort of system, so that pieces don't become mixed up.

After all of the metal parts are cut to rough length, file the ends clean if necessary. Clamp the piece in the vise with the end face up, using the soft jaw covers, and carefully file the end faces flat. Be careful to keep the file horizontal, and only file deep enough to get below the marks from the saw blade. It is better to err on having a part slightly too long than too short, so be sure not to file too far even if it means leaving an end face with some fine saw marks remaining. File a slight chamfer on each end face edge to remove any sharp burrs.


labeling parts

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108

To mark the locations of the holes to be drilled on the parts, a 6" engineers scale, felt tip marker, circle template, the scratch awl, and a fine tip felt pen were used. A disposable technical pen in an .03 tip width works well. A carpenters square can be used on the longer parts. It ensures that measurements are accurately made from the end face. Be cautious if using a carpenters square. While some edges are marked in traditional 1/8", 1/16" or 1/32" divisions, others may be marked in 1/10" or 1/12". This can cause serious errors in marking if not careful.


MomusDesign

Use the felt‐tip marker to color a zone on the part where the center line of the hole is located. Measure and scribe a fine line across the part at the center of the hole location. Also scribe a line at the side to side distance to create a scribed crosshairs at each hole location. Scribing the line that runs parallel to the length of the aluminum parts may be difficult due to marks in the surface from the extrusion process. These might pull the awl into them and create an inaccurate line. If this happens, color back over any inaccurate scribe lines and try re‐scribing. Use the circle template, lined up to the scribed crosshairs, to draw the outline of the hole with the fine felt‐tip pen. Also, write the diameter of the hole directly on the part to avoid having to consult the drawings later to re‐determine the hole size. With everything clearly marked on the part, little thinking will be required when drilling the holes. Mark the tapped holes in a similar manner. A drill press is highly recommended to achieve the necessary accuracy when drilling holes. It is almost indispensable, and they can be purchased quite inexpensively. Make sure it has enough quill travel and throat clearance to handle all of the drilling requirements. A drill press vise of some sort is also very helpful. The drill press used here was a very inexpensive homeowners quality, equipped with a compound cross slide vise. Take some time to adjust the drill press so that the table is exactly perpendicular to the quill. When drilling, especially on the aluminum parts, always use a proper cutting fluid. Drilling aluminum dry will quickly destroy the drill bit. The drill bit itself can be used to accurately clamp the part. Extend the quill down alongside the part. Push it up against the drill bit while clamping it in place. This will ensure that it is parallel to the length of the bit and quill travel.


hole layout

page

109

Clamp the parts to be tapped firmly in a vise (use the soft jaw covers, unlike what is shown here). Secure the tap into the tap handle and start it into the hole. Be sure to use plenty of tapping fluid that is designed for tapping aluminum. WD‐40 can be used if it is not available. Using tapping fluid is crucial. Taps will not last long when tapping aluminum without it, especially the smaller sizes, possibly not even making it through the first hole.


MomusDesign

If you have never tapped a hole before, it is highly suggested to do a trial run on an extra piece of aluminum. Use the properly sized drill bit and drill a few holes to be tapped 1/4‐20. It is worth getting used to the experience on a scrap piece, as taps can be quite fragile. Any side loading can immediately snap them off, as can excessive chip loading in the flutes. A broken tap can be nearly impossible to remove from the part without specialized equipment, so a tap broken off in a final part will most likely require starting completely over with a new piece. Better to break a tap in a piece of scrap. That said, with the proper technique and a good lubricant, tapping holes in aluminum is quick and easy. Also recommended is tapping all of the 1/4‐20 holes first, to get comfortable with the technique, before attempting the 10‐32 holes. The smaller tap size is less forgiving of error and will break much easier. Turn the tap into the hole and check the alignment as it starts to bite. Look at the tap from both the front and the side to make sure it is exactly perpendicularly to the part. The only opportunity to make any correction is during this first partial turn of the tap. Even then, the amount of correction possible is minor. Taps are very brittle and cannot withstand ANY side loading. As the tap is threaded into the hole, stop every turn or so and back the tap out a partial turn to break the chips before going deeper. When the tap comes out of the backside of the hole, clean the chips off of it with a spray lubricant before threading it back out of the hole.

version 2.1

With the tap removed, clean it thoroughly of all chips before starting the next hole.

copyright 2013

tapping holes

page

110

There are a few large diameter holes that need to be cut, as well as some unique shapes cut from plate. While the large diameter holes can be cut with a hole saw if it is available, the following technique, called stitch drilling, can be used for any of these cuts. A series of closely spaced holes, that slightly overlap, are drilled along the edge of the cut line. This will remove a plug of material. Final shaping can then be done with a hand file. This can be used both for parts cut from thin (3/16") stock, as well as out of considerably thicker plate.


MomusDesign

In the example to the right, a large round hole is being cut. A circle template was used to draw a concentric circle that is smaller in diameter than the desired hole by the diameter of the drill bit being using. For example: for a 1.5" dia. finish hole size, using a 1/4" drill bit, a 1.25" circle was drawn. A series of slightly overlapping 1/4" holes were then drawn using the circle temple, placing their center points on the inner circle. These were simply spaced by eye. The center point of each 1/4" hole was center punched. The holes were drilled, removing a plug of material as shown. The same process can be used for thicker stock, as seen in the images to the left. Both parts were finished to final size by hand filing. If the holes do not completely overlap, it may be difficult to remove the waste material. A cold chisel may be used to cut any remaining webs. The waste on the part to the left was cut off with a hacksaw. The best diameter of drill bit to use for this is a compromise, and will require some judgment. The smaller diameter drill bit used, the less material that will need to be removed with the file during clean‐up. However, the smaller the diameter the bit, the more difficult it is to drill sequential holes that barely overlap. A larger diameter bit makes it much easier to accomplish this overlap, but requires more material removal with the file, hence requiring more time. Generally, the smallest bit that will easily allow drilling holes that overlap the previous ones should be used. A bit around 1/4" dia. will provide a good starting point. If in doubt, use a larger bit.


Clamp the part in a vise and finish file to the final size.

stitch drilling

page

111

There are several wood components with large holes, which are easiest to cut with a hole saw. Use of the hole saw is discussed on page 91. Likewise, there are several aluminum components which may also be cut using the same two sizes of hole saws (1 1/4" and 1 1/2".) Use of a hole saw will be especially helpful when fabricating the Z motor mounts. These two parts have a concave radius groove cut out of their inner faces, which can easily be cut with the 1 1/4" hole saw. The saw must be of the type that can be used to cut metal. The easiest way to accomplish this cut is by clamping the two parts together, with a 3/4" spacer between them, and drilling as one unit. In the top two images, the parts are clamped in a bench vise to measure and mark the hole location.


MomusDesign

As when using the hole saw in wood, pre‐drilling smaller holes for chip clearance will improve the smoothness of the cut. Drill these holes just to the inside of the larger hole that will be cut. An additional hole can be drilled at the center, to act as a guide for the pilot drill in the center of the hole saw. This is optional, and was not done here. Clamp the work in the drill press vise and carefully align the hole saw to the marked circle. Use a low spindle speed on the drill press. Use a cutting fluid or WD‐40 while making the cut.

The completed parts with neatly matched grooves are shown to the right. No further finishing was required.


hole saw

page

112

The carriage assembly has several parts that require holes drilled while they are clamped in alignment with each other. Gather the following five parts together, as seen in the image to the left: #13‐ carriage block rear lower #16‐ carriage block front right #17‐ carriage block front left #19‐ lower spacers


MomusDesign

Begin with lower rear block, one lower spacer, and either of the front blocks. As seen in the top and middle images to the right, using an accurate square, scribe guide lines that correspond to where the edges of the spacers will be when the parts are assembled. Clamp the 3 parts together with a 5/16” bolt, as seen in the lower left image. Use the scribed lines as guides to keep the front and lower blocks square to each other, and centered properly. Double check that they are square to each other and fully tighten the bolts. Triple check that left and lower blocks are square to each other.

Flip the assembly over and clamp it into a vise on the drill press table. Check again that the parts are square to each other. Insert a 3/16” drill bit into the chuck. Lower the quill next to the parts to make sure that the drill press spindle is parallel to the edges of the parts. This drilling operation will be going through the thickness of all 3 parts, so the drill needs to go as straight through them as possible. Carefully align the drill bit with the existing holes of the lower carriage block and drill down through the other two parts. Align the bit carefully so that the existing holes are not reamed out larger.


carriage match drilling

page

113

Take the parts out of the vise and disassemble them. Mark them first so that they can be put back together with the spacer in the exact same orientation. Carefully clean the parts of any oils, cutting fluids, etc.. With a hammer, drive two 3/16” x 2” roll pins down through the 3 parts to re‐ assemble. With no bolt, the joint connection between the parts should have no perceptible play or movement.


MomusDesign

Repeat the procedure with the right side parts. For accurate alignment, use the square as well as taking multiple measurements between the left and right side carriage blocks to make sure they are exactly parallel. This distance should measure 2.625".

Drive the roll pins down through the second joint, as seen in the image to the left. With no bolts installed, as seen to the right, the assembly should be strong and rigid, with no play. The 5/16" bolts will be reinstalled during a later assembly step, to give additional strength to the joints.


carriage roll pins

page

114

The router clamps are fabricated from thick aluminum bar stock, and have a complex series of curved cuts. While a metal cutting bandsaw would be a helpful tool to make these cuts, the pieces here were made using the stitch drilling technique outlined on page 111. The basic principle is the same: drilling a closely spaced series of holes and then hand filing to final size. Due to the thickness of the material, it is beneficial to use the smallest practical size of drill bit diameter, as a larger bit will leave more material to be removed across the face of the part thickness. A 1/4” drill bit was used in these photos.


MomusDesign

As the geometry of the parts is relatively complex, it may be helpful to print the drawing sheets and cut them out for use as patterns. If printing patterns, use durable heavy paper or card stock. After printing, measure the longer dimensions to check that the sheet has accurately printed to scale. If not, adjust the printer scale setting. Unfortunately, printer scale error is often less than 1%, which is enough to cause a slight inaccuracy but not enough to be able to correct through the printer driver. Carefully cut the pattern out with a sharp razor blade.

The parts shown here were laid out directly on the stock, without aid of paper patterns. The matching components (mount and clamp) were marked together as one unit. To do so, a wood block of the correct thickness was clamped between them. Fillet curves were marked with a circle template and fine felt tip pen. As seen in the image to the left, these were the first holes to be drilled in the stock. After drilling these holes, the closely spaced stitch holes were placed along the rest of the part outline, as seen in the image to the right.

A hacksaw was used to remove the excess material. On the mount component, a hole saw was used to drill close to the surfaces that will contact the router body. This can be seen in the image to the right. While the hole saw is a smaller diameter than the router body, it can cut much closer to the layout line, and will require less filing than a series of small diameter stitch holes. After removing the bulk of the stock, as seen in these photos, the parts were hand filed to remove the remaining material.


cutting router mounts

page

115

The drive belts are secured with fabricated clamps that have corresponding grooves cut into them. This can be achieved with a simple hacksaw and some patience. No filing was done in any of these photos, this was all done with just the hacksaw. Hold a length of the belt securely on the piece of stock to be marked. Scribe short marks that align with the width of the root of the belt teeth. As you move along the belt marking teeth, move your head as well. It is important that you are looking exactly straight‐on at the belt while marking to avoid parallax error.


MomusDesign

With the teeth widths marked, use a square to extend the scribe lines across the width of the stock. With the stock firmly clamped in the vise, slowly begin to use the hacksaw to cut out the grooves. Keep the saw as horizontal as possible and use a finger or two as a guide against which the side of the blade rests. Think of the saw blade as a long narrow file. Tilt the saw to the side to widen the slot if necessary. Alternatively, install two blades in the hacksaw handle. This will effectively create a wider blade that may more closely match the width of the grooves.

When the belt is installed on the machine, these parts are exerting clamping force against the belt, therefore the depth of the grooves do not need to be the full tooth thickness. More important is that the center to center spacing of the grooves matches the belt. As long as there is some small amount of groove it will prevent any belt slippage once clamped together. Cutting these grooves is much easier than it may seem, and the work progresses quickly.


belt clamps

page

116

With all of the 1/4” threaded studs cut to length, gather all of the metal parts together. Locate all of the parts that will have studs threaded into them. Make sure that the threads on all the parts are clean and free of any oils, tapping fluids, etc. Clean the parts with a degreaser if necessary. Cotton swabs can be used to reach into the holes.


MomusDesign

The studs will be adhered into their holes with a thread‐locking compound so that they will not turn when nuts are tightened onto them. Since it can be very difficult to remove these studs once they are bonded in place, it is highly advisable to do a trial assembly of all parts that are held together with studs. This will allow checking that all stud lengths are correct. Using plain nuts can help with a trial assembly, as using the nylon‐insert lock nuts will simply cause the stud to turn deeper into the part. Following the exploded‐view drawings on pages 30‐33, thread the correct studs into the parts. The stud lengths are calculated for 1/2" thread engagement into the parts. With all of the studs temporarily in place, follow the relevant directions on the following pages to complete a trial assembly of mating parts. If all seems to assemble together correctly, disassemble the parts, keeping stud lengths organized.

Apply a couple of drops of “permanent” thread‐locking compound to the end of the stud. A small amount is sufficient. The tip of the tube can be used to spread the compound around the circumference of the stud. Thread the stud into the hole to the required depth. Set the parts aside to let them cure. Leave them undisturbed for a full day before beginning any assembly. If any of the studs need to be removed, the permanent thread‐locking compound requires the application of heat to soften it. Heat the part in an oven at 400 degrees F, or use a propane torch applied to the part. The stud should now be able to removed with a pair of locking pliers. After cooling, chase the threads in the aluminum part with a tap to remove thread‐locking compound residue before installing a new stud.


installing studs‐ Assembly

page

117

Begin assembly of the metal parts by attaching the Y rail (part # 11) to the gantry tube (part #02). Assemble using (7) 1/4‐20 x 1/2"socket head cap screws and lock‐washers. The cap screws need to have full thread engagement in the rail, yet not protrude beyond its outer face or they may strike the carriage as it slides. Achieving this proper engagement may requiring adjustment by stacking several lock‐washers together. Here, two were used under the head of each screw.


MomusDesign

Use a hex key that is long enough to feed the cap screws through the 1/2" holes in the back face of the gantry tube. It may be easier to do this if the front of the gantry tube is oriented facing up. This way, gravity is holding the cap screw on the hex key as it is fed up through the holes. Get all 7 of the screws threaded into the rail, but do not tighten fully. Tighten the two outer ones until they are just snug enough that the rail can still be moved around when pressure is applied. Check to make sure the threads do not protrude beyond the face of the rail.

Use a scale and measure both top and bottom, and at each end of the rail to make sure it is exactly centered on the gantry tube. When it is centered, tighten all of the screws down fully. As seen in the image to the left, the gantry tube should extend beyond the rail at each end by .75".


gantry rail‐ Assembly

page

118

As per the diagram to the left, and image to the right:

MomusDesign

This assembly should now slide into the slots on the left side of the gantry, and look like the image to the right. Make sure that the correct end of the part is facing forward. Depending on the type of washers being used, and their particular outside diameter, it may be necessary to file a flat on the four washers that are inside the gantry tube, as seen in the top right image. SAE dimension washers should fit without modification. USS dimension washers are larger in diameter.


Washers

Thread a nylon insert lock‐nut, with two flat washers above it, onto each of the studs in part #03, marked “gantry left top”. Thread the nuts nearly to the top, leaving about 3/16" of an inch between the washer and the part. Thread another nut onto each stud, this time with the nylon insert going on first. To do this, if may be necessary to thread the nuts on in the conventional direction first, perhaps even a couple of times, so that the stud forms threads into the nylon insert. Even having done this, it may be difficult to get the nuts threaded on straight. Use caution and do not force the nut onto the stud if it is not going on straight. Thread these nuts up the stud so that they are about 1/2" below the first set. Slide a flat washer up each stud so that it is against the inverted nuts.

Using a square, align the inserted part so that it is perpendicular to the gantry and tight against the end of the Y rail. Tighten the top set of nuts, being careful to keep everything perpendicular. Next, thread the inverted nuts back down the stud so that they are just putting a very light pressure against the bottom inside face of the gantry tube. The purpose of these nuts is to keep the gantry tube from being crushed under the pressure of tightening the bottom part. With the lower nuts in contact with the inside of the gantry tube, slide two washers and part # 01 (gantry bottom), up the studs.


left gantry‐ Assembly

page

119

Using the square to make sure part #01 (gantry bottom) is also perpendicular to the gantry, install another set of flat washers and lock‐nuts to hold it in place. Tighten securely. The assembly should look like the image to the left. Note the drawings and images carefully for the placement of the four washers between the gantry tube and the other parts. These are necessary for correct spacing. Using the same procedure, and sequence of nuts and washers, install parts #01 (gantry bottom) and #04 (gantry right top) on the right end of the gantry tube. Parts #05 (gantry spacer) and #06 (gantry outer right) will be installed next. Before installation of parts #5 and 6, thread two 10‐32 x .75 setscrews into the holes as seen in the image to the right.

MomusDesign

Washers

Note that part #06 (gantry outer right) is not quite symmetrical and it is possible to accidentally install it upside down. When installed in the correct orientation, the vertical hole at each end should align exactly across to a similar set of holes in part #04. With these parts in the correct orientation, install washers and nuts onto the studs and tighten to secure them. All three of the top parts should be flush across their top faces.


WASHERS

The gantry assembly should look like the image to the left. Next install parts # 07 and #08 (Y motor mounts) as shown to the right. Note that these parts are different. The holes for the motor attachment are offest to the inside. Closely look at the image and the exploded‐view drawing to note which side they face. If in doubt, hold a motor up to the mounts to make sure the holes align. Install a washer and nut on each motor mount stud. Do not tighten then down fully. Tighten the nuts just to the point where the mounts can be moved around by hand.


right gantry‐ Assembly

page

120

Locate the carriage parts as seen in the image to the right. They are parts: #12‐ carriage block rear upper #18‐ upper spacers the sub‐assembly from page 113 (parts #13, #16, #17, #19) (4) 5/16”x 3” grade 8 bolts, nuts, and washers.


MomusDesign

Begin with the sub‐assembly that is currently held together only with roll pins. As seen in the image to the right, install two bolts, with washers and nuts. Use lock‐washers if the nuts are not lock‐nuts.

Install the upper rear carriage block (part #12) and the two upper spacers (part #18) as seen in the image to the left. With the nuts lightly snug, measure between each end of parts #12 and #13 to ensure that they are exactly parallel. This distance should measure 2.625". Adjust as necessary. When satisfied that they are parallel, tighten the top two bolts fully. If a torque wrench is available, tighten all four bolts to 25 lb/ft. Double check parallel alignment to ensure parts have not moved during tightening.


carriage blocks‐ Assembly

page

121

Organize the four bearing blocks to be attached to the carriage assembly. Note that one (part #15) has a stud installed for later installation of the Y belt clamp. This bearing block is installed in the top position. The other three bearing blocks (part #14) are identical.


MomusDesign

Using the exploded‐view drawing on page 31, and the images on this page, install the four bearing blocks in their correct orientations.

Next, install the Z motor mounts (parts #20 and #21) as shown in the images to the left and right. Use a square to position them perpendicular to the carriage. Take care to set them as square as possible, as any error will later cause misalignment of the Z axis leadscrew. Note that the nuts are very close together, and this may prohibit use of washers. They are also close enough together that tightening the first nut so its flat is facing the second nut will give more working space for a wrench.


carriage assembly

page

122

Locate the Z axis parts as seen in the image to the right. They are parts: #24‐ z rail #25‐ z rail block #26‐ nut plate block


MomusDesign

Assemble the parts together as seen to the right. Install nuts on the top and bottom studs of the Z rail. Do not tighten the nuts holding the nut plate block at this time. With the top and bottom nuts lightly snug, adjust the Z rail block so that it is exactly centered on the width of the Z rail. Take multiple measurements on each side, and top and bottom. When centered, tighten the two outer nuts.

Thread the nuts holding the nut plate block so that they are not quite snug against it.


Z axis rail assembly

page

123

Note that in some locations this bolt has a modified head. 5/16‐18 x 1 1/2" bolt bearing washer 5/16 lock nut

10‐32 set screw


MomusDesign

NOTE: In addition to this series of photos, refer to the exploded drawing on page 32 that depicts the bearing locations. It is sometimes difficult to have one view clearly show all of the bearing locations in a given step, so this drawing may help to clarify.

The next step is to populate the gantry and carriage with bearings. Most of the bearings are attached in the configuration of bolt, bearing, washers, and nut that is show in the above left diagram. This sequence of parts is also seen in the images to the right. As each bearing is installed, thread the lock‐nut on far enough that there is just a very small amount of clearance between the washers and the part. The bearing should just be able to slide slightly along the face of the part, but not rock or feel loose.


bearing installation

page

124

Begin by installing the four bearings in the left end of the gantry, that are shown in the images to the left and right. Note that the lower bearings use bolts with modified heads for clearance. These are circled in the image to the right.


MomusDesign

The left end of the gantry also uses two bearings as an idler bearing for the belt drive. These can also be installed during this step. Use a 5/16‐18 x 2.5" long hex head bolt or socket head cap screw. Two fender washers are used as flanges, and a short stack of standard flat washers are used as spacers, to achieve the correct height. When installed, the underside of the top fender washer should be 1" from the top face of the upper gantry block.

The right end of the gantry uses four bearings installed in the same positions as the left end. In addition, there are four more bearings positioned from the underside, as seen in the left image. The right end of the gantry has a total of eight bearings installed. The lower bearings on the right end of the gantry also use bolts with modified heads. They are circled in the image to the left.


gantry bearings

page

125

The four bearing blocks (parts # 14 and 15) have a longer bolt that goes through them, holding a bearing on either side of the aluminum block. The bearing assembly sequence is seen in the image to the left. Slide one bearing onto the socket head cap screw, and then one washer. Note that there is no washer between the head of the socket head cap screw (5/16‐18 x 3") and the bearing. Insert this through the bearing block. Next slide a washer, bearing, another washer, and then the lock‐nut.

MomusDesign

Install all of the bearings onto the carriage assembly. Study the images on this page, and the illustration on page 32, for the positions of all bearings. This step will be installing a total of 24 bearings on the carriage assembly.


Note that four bearing locations require the use of modified bolts with thinned heads. Two of these are circled in red in the lower right photo. The other two are obscured in these photos, but are in the same positions on the other side of the carriage.

At the location of each of the bearings that has been installed on the carriage, thread a setscrew into the hole that is perpendicular to it. For now, just thread these in a few turns, so that they do not fall out.


carriage bearings

page

126

Measure the outside distance of the lower gantry blocks, as seen in the left and right images. It should measure 24". The dimension can be adjusted by repositioning the components on either end. Bringing them closer together may require trimming the length of the Y rail slightly. Before making any adjustments, consult the measurement of the base that was taken on page 99. For the best fit, the gantry measurement take here should be exactly 1" less than the measurement of the base taken on page 99.


MomusDesign

After assuring that the correct 1" difference between the two measurements can be achieved, remove the components from the left end of the gantry. Fully remove the lower piece. Slightly loosen the remaining nuts, and the assembly will slide out of the slots in the gantry tube.

Slide the carriage assembly onto the gantry, feeding the Y rail between the bearings. There should be enough clearance between the bearings and the rail that it slides on easily. If the bearings do not move far enough apart to allow the carriage to slide onto the rail, stop and investigate why. If there was inaccuracy in drilling holes, there may not be the proper range of adjustability for the bearings. If this happens, look closely to determine which bearings need to be able to slide further away from the rail. Remove them from the carriage assembly. The holes can then carefully be filed to elongate them, giving more adjustment range. Re‐install the components on the left end of the gantry. Use a square to ensure they are perpendicular to the gantry, and remeasure the dimension taken at the top of this page. Be careful in handling the final gantry assembly, as the carriage will slide very easily and has significant mass, which can easily lead to smashed fingers.


carriage installation on gantry

page

127

As seen in the images to the left and right, install a 10 tooth timing belt pulley onto the shaft of a stepper motor. A measurement of 7/8" from the face of the motor to the outer pulley flange should result in a correct belt alignment.


MomusDesign

Install the motor with four 10‐32 x 1" socket head cap screws, or machine screws. Place washers between the motor mounts and the motor, as shown to the left, to raise the round boss on the end of the motor clear of the mounts. Two flat washers were sufficient here for clearance. Tighten the motor to the motor mounts.

Hook the 250 tooth belt around the left idler pulley. Remove the motor, still attached to the mounts, from the gantry and hook the other end of the belt around the motor pulley. The motor and mounts can now be lowered back down into position, and the nuts re‐installed on the mount studs.


gantry belt drive

page

128

Tighten the nuts on the motor mount studs so that they are not quite snug. Insert a hex key through the holes as shown in the image to the right, so that it engages with the setscrews. Tighten the setscrews, working alternately from one to the other, to tension the belt.


MomusDesign

When the belt is at sufficient tension, fully tighten the nuts on the mount studs. Be careful to not overtighten the belt, as the setscrews are capable of applying significant pressure.

Install the Y belt clamp as shown in the image to the right. Before tightening, it is important to install a small spacer behind the top side of the clamp. This serves to help the clamp put even pressure against the full width of the belt. The spacer is circled in red. The spacer used here was cut from paper mat‐board and measures slightly more than 1/16" thick. Note that the clearance between the stud and the inside of the belt is very close. If contact with the belt occurs, especially at the motor end of carriage travel, it may be necessary to shorten the stud slightly. Depending on tolerances, it may even be necessary to trim the thickness of the nut, or the thickness of the belt clamp.


gantry belt drive

page

129

Next to be installed are the Z axis motor and Z cable plate (part #22). With two lock‐nuts and washers, install the stud into the cable plate as seen in the image to the left.


MomusDesign

Install the motor and cable plate to the Z motor mounts with 10‐32 x 1.75" socket head cap screws or machine screws. The assembly should look like the images shown on this page.


Z axis assembly

page

130

Slide the Z rail assembly into the carriage bearings from the bottom. It may be easiest to work by laying the gantry assembly on its back.

NOTE: See the addendum on page 171 for an alternative lead‐ screw assembly that includes the addition of thrust bearing. Following the procedure in the addendum is HIGHLY RECOMMENDED.


MomusDesign

Assemble the anti‐backlash nut to the bottom of the nut plate (part #27) with four #4 machine screws and nuts, as seen in the image to the right. Thread the leadscrew about half way into the anti‐backlash nut.

If using a motor coupler made of Delrin plastic, an additional set screw should be added, as shown in the image to the left. Drill and tap with #10‐32 threads for this set screw. This can then be tightened against the flat on the motor shaft for a more secure connection.

Thread the motor coupler onto the top of the leadscrew. Thread it on so that the end of the leadscrew is aligned with the slot that is cut through the coupler. The assembly should look like the photo to the left.


Z axis assembly

page

131

Position the leadscrew assembly as in the image to the right, so that the motor coupler is aligned with the motor shaft. Slide the coupler onto the shaft and tighten its screws to secure it to the shaft.

MomusDesign

Let the Z rail assembly slide down so that the studs on the bottom of the nut plate block go through the holes in the nut plate.


NOTE: See the addendum on page 171 for an alternative lead‐screw assembly that includes the addition of thrust bearing. Following the procedure in the addendum is HIGHLY RECOMMENDED.

Install two lock‐nuts as seen in the image to the right. Thread the nuts on so that they are not quite touching the nut plate. Note that the studs are close together, which may prevent the use of washers.


Z axis assembly

page

132

The next step will be to install the X rails to the machine base. Begin with the four rail parts shown in the image to the right: part #28‐ X rails part #29‐ X rail angle left part #30‐ X rail angle right


MomusDesign

Assemble the rails to the angles with hex head 1/4‐20 x 1/2" bolts. Use a single lock washer beneath the head of each bolt. As seen in the lower left photo, the threads will protrude too far beyond the face of the rails. Like the Y rail that is attached to the gantry, the threads must not protrude beyond the rail face. Do not use additional washers beneath the heads of the bolts to correct this. The thread length of the bolts must be shortened. This can be done before inserting the bolts, or as was done here, carefully ground down after assembly with a disc grinder.

With the bolts appropriately shortened, adjust the rails so that their lower edge is flush with the bottom face of the angles. Tighten the bolts so they are snug tight. Do not fully tighten, as further adjustment of the rail positions will be done later.


X axis rail installation

page

133

Using four #10‐32 x 1" socket head cap screws, or machine screws, install the X stepper motor (with pulley installed) and right plate (part #31) to the right angle and rail. At this point there will only be two screws sandwiching the assembly together, so use caution when handling. Note that the top edge of the X rail angles have been ground down in height. This will provide clearance for bearings that contact the edges of the X rails.

Measure between the inside faces of the X rails at the front and rear of the machine as shown to the right. If everything has been constructed accurately, this dimension should be 24.125". The rails need to be as parallel as possible, so if the measurements do not match, loosen the lag bolts slightly and carefully adjust the positioning. There should be less than 1/32" discrepancy between the front and rear measurements. Aim to achieve rails that are as parallel as your measuring method will allow. With the rails positioned parallel, install the remaining lag screws and fully tighten all of them.


Secure the plates/angles to the base with the lag screws and a flat washer beneath each head. Fully tighten the 7 lags on each side that only go through the plate. Adjust the angle/rail assemblies so that there is .1875" between the edge of the plate and the rear face of the X rail, as shown in the image to the right. Measure at front and rear points along the rail to maintain a consistent .1875" overhang. This will provide an initial adjustment. Tighten the front and rear lag screws that go through both plate and angle so they are snug, as seen in the image to the right.

MomusDesign

Place the assembly from the step above into position on the machine base. Place the left plate (part 32 X) and left rail/angle assembly into position on the other side. The correct positioning of these parts is with the rear faces flush with the rear face of the base, as seen in the left image.

.1875"

24.125"


X rails

page

134

Once the X rails are parallel, attempt sliding the gantry assembly onto the rails, as seen in the photo to the left. Go slowly and carefully with this. There is little clearance between the lower bearing bolts and the machine base, and the bolt heads can gouge the surface of the base if the gantry is not slid exactly straight onto the rails. The tight clearance can be seen in the image to the right.


MomusDesign

To keep the bolt heads from rubbing, a preliminary adjustment should be made to the bearings. This will keep the gantry centered within the rails and allow it to travel smoothly along the length of the rails. A complete alignment to the rest of the bearings will be performed later. Begin by adjusting the two bearings circled in the right image. Hold sideways pressure against the gantry, pushing these two bearings against the face of the X rail. Use the set screws to adjust the bearings so the the two lower bearing bolt heads clear the base by about 1/16". Place a square between the X and Y rails to check that they are perpendicular to each other. Tighten the nuts to secure the bearings that have just been adjusted.

As seen in the middle left image, adjust the two bearings that ride against the rear face of the right X rail. Tighten them so that the gantry feels rigidly attached to the rail, with no perceptible play. Readjust as necessary to get the gantry at exactly 90 degrees to the X rails, as seen to the left. Consult the adjustment techniques on page 161 to help make this alignment.

90

Adjust the two bearings circled in the image to the right. They should be set so that the gantry is raised high enough that there is no interference between any parts as it is pushed forward and back along the rail.


This series of adjustments should allow the gantry to smoothly roll.

gantry and preliminary adjustment

page

135

When the gantry is rolling smoothly, with no interference at any point along its travel, install the X belt components. Begin with the X belt pulley adjuster (part #33). Install the hex head bolt into the threaded hole. This is an uncommon size of hex head bolt and may be difficult to source locally. If one cannot be easily located, a 5mm x .8 pitch metric bolt may be substituted. The thread pitch is nearly identical to the #10‐32 size, but the outside diameter is a few thousandths of an inch larger. The 5mm bolt threaded into the #10‐32 hole will be serviceable in this situation. If the metric bolt will not thread in easily, run the #10‐32 tap through the hole again.


MomusDesign

First, hook the 200 tooth belt around the pulley on the X stepper motor. Assemble the bearings to the pulley block with 5/16‐18 x 2" socket head cap screw or hex head bolt. As on the gantry pulley, use two fender washers as flanges. Use a single flat washer between each fender washer and the bearings. Hook the other end of the belt around the pulley assembly and drop it down into position, as seen in the left image. As seen to the right, insert a 5/16‐18 x 2.5" socket head cap screw through the hole that is adjacent to the pulley block. Install a washer and nut on the other end of the screw and tighten. This cap screw serves as a solid stud, against which the pulley adjuster will push.

Install a washer and nut on the bottom of the idler pulley center bolt and tighten so that the block is just free to slide sideways. With a small wrench, back the small hex bolt out, to put tension on the belt. When proper tension has been achieved, tighten the nut. Install the belt plate (part #09) and the belt clamp (part #10) as seen in the image to the right. As on the Y belt clamp, install a small shim behind the top edge, as circled in red.


X belt assembly

page

136

Using the exploded‐view drawing on page 35, assemble the cable arms, as seen to the left. Make careful note of where the large diameter washers with enlarged holes are placed. The bearings in this assembly are being used as thrust bearings, which is not the direction in which they are intended to be loaded. To avoid premature wear of the bearings, the nuts on the studs must be adjusted so that they are tight enough to hold the assembly rigid, but not so tight as to introduce excessive side loads. The bearings are being used in this manner because they are the same type that are used throughout the machine, and are inexpensive when sourced in bulk. They could easily be replaced with proper thrust bearings if desired.

Install the assembly to the gantry, as seen in the upper right image. The cable arm assembly should cantilever from the gantry without sagging.


MomusDesign

Push the gantry all the way to the rear of its travel. Working from beneath the gantry, hold the cable arms so that they are as horizontal as possible, and mark the locations of the holes in the cable arm mounting block where it contacts the rear plate.

Pull the cable arm assembly away from the machine base and drill a 1/8" pilot hole in the center of the hole marks. Install the mounting block to the base with two 1/4" x 1.25" lag screws, as seen to the right.


cable arm assembly

page

137

To facilitate alignment of the machine to a high level of accuracy, a perfectly flat surface should be used as a reference plane, from which all measurements can then be based. There are several possible methods of doing this. The simplest is to use the wooden bed of the machine as a reference surface. If it can be determined that it is adequately flat, it can be used in this capacity. Most likely, it will have enough deviation from true flat to require using a flatter surface. This can be done in several ways. One is to temporarily place an object known to be very flat, such as a surface plate or lapped glass plate, securely on the bed so that it cannot move during the alignment process. A second method, used here, is to pour a thin layer of epoxy resin on the bed to level it. An epoxy with a very low viscosity will self‐level and result in a surface that is very flat, creating a relatively low cost surface plate that is integrated into the machine.


MomusDesign

Prior to pouring the epoxy, the bed area must be as level as possible so that the epoxy will be a consistent thickness. If there is a large difference in thickness of the liquid epoxy, surface tension can result in an imperfect finished surface. A larger volume of epoxy would be required to overcome this tendency. To level the machine, place it on a solid surface that cannot move during the duration of the time the epoxy requires to cure (at least 24 hours). The machine can be placed on four bolts with nuts threaded onto them, to serve as adjustable feet. The bolts used here were 3/8” diameter.

With the machine on a solid and stable surface, use a high quality level to set the bed of the machine as level as possible. Check for level in multiple directions, as seen in the images on this page. Use the bolts to adjust the corner heights of the machine as necessary to achieve a level machine bed area. Note that if the bed area is not perfectly flat, which is to be expected due to typical wood construction tolerances, achieving a “level” bed may be a compromise between errors in several directions. Find the best average of the errors that is possible.


epoxy bed

page

138

To pour the epoxy, it is necessary to establish a watertight dam to contain it to the bed area. This was done here with strips of painter's tape applied to the front and rear edges of the bed. The poured epoxy will only be approximately 1/8” thick, but make sure the dam is significantly higher than this. What is most important is that the area will have no leaks. The epoxy is very thin and will run out of the smallest crack or area of porosity. Make sure the joint between the bed of the machine and the vertical skin panels is watertight. If in doubt, additional paint may be applied to seal very fine openings, or a caulk may be used for larger gaps.


MomusDesign

Use an epoxy with as low a viscosity as possible. The brand used here has a viscosity of about 550 cps, which is quite thin. Note that the warmer the liquid epoxy resin, the thinner it will be. However, if it is warmed too much, it will cause it to harden too fast. An ideal compromise is to get the epoxy to about 85‐90 degrees Fahrenheit. The temperature of the room should also be high. If it is not, the warmed resin will cool very rapidly when spread thin. The resin can be warmed by placing the closed containers in a bucket of hot water for 15‐20 minutes. Warm the resin before mixing the two components together to activate. Use a slow hardener to allow maximum time for the resin to flow out to a flat surface. Mixing a total of 24 fluid ounces of epoxy resin will result in an average thickness of just under 1/8”. This is about the minimum amount to coat a base that is already reasonably flat. 32 fluid ounces is suggested, as it will flow out across the surface more easily. The more inaccurately the wood base was constructed, the more epoxy it will take to arrive at a perfectly level coating of epoxy. Although a high quality epoxy will have few solvents and will produce very little odor, make sure there is adequate ventilation in the work area. Set up an exhaust fan if possible. Double check that the machine bed is as level as possible and mix the epoxy. Use a graduated cup for accuracy and follow the manufacturers mixing directions.

Pour the mixed epoxy into the bed area, and use a spreader to try and achieve a consistent thickness across the surface. The resin will self‐level, so it need not be perfect, but the entire surface should be coated, including into the corners and edges. Be careful both when mixing the epoxy as well as spreading it that excessive air bubbles are not introduced. Trapped air bubbles will stand proud of the flat plane of epoxy when dried. After spreading, allow the resin to harden for at least 24 hours. Do not disturb the the machine during this time.


epoxy bed

page

139

The cover assembly is attached to the base along its lower rear flange by four screws. Other than these screws to secure it, the cover primarily rests on the machine base under its own self‐weight.


MomusDesign

Prior to attaching the cover, thin foam strips were applied to the edges that will contact the machine base. These were also applied to the surfaces where the two halves of the cover come together. The foam will cushion the cover to prevent vibrations, as well as seal any gaps to prevent sound transmission. The foam used here was cut from sheets of a medium density foam rubber that was purchased at a craft store. It was applied with a high temperature hot‐melt glue gun.

Two fluorescent strip lights were installed in the top inside of the cover. Slots were routed in the bottom of the flange to allow their power cords to exit the cover. The foam strips were installed in a manner to allow placement of the cords beneath them.


cover assembly

page

140

A latch was not installed on the front door, as it is held in place during machine operation by its self‐weight. However, a latch may be installed if desired. Lifting the front door, it can simply be rested on the rear cover half.


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A rear door is fitted, to cover the hole at the rear of the machine. The intent of providing the door is that it can allow stock that is longer than the machine bed to pass through, giving a larger effective work area. Depending on anticipated frequency of use of this feature, the rear door can either be screwed in place, as seen here, or can be installed with hinges for easier operation.

Strips of foam were also placed around the perimeter of the rear door face, where it will contact the machine base. A hole was cut in the door with the hole saw for passage of the router power cord. The door was fastened with six wood‐screws.


cover and rear door

page

141

INSTALLATION OF ELECTRONICS: A complete guide to installation of the electronic drive components is beyond the scope of this manual. This is largely due to the vast number of different drive manufacturers and models, each with their own wiring requirements.

General Electronics Installation Sequence: 1. Install wiring to motors

While the installations shown here are for specific models of drive boards, the general procedure may be similar for models of boards from other manufacturers.

3. Connect power supply to motor drive.

Machine operation is possible with a minimum of components: a power supply, drive board, and stepper motors. However, the system should not be considered complete without the addition of an emergency stop switch and limit switches. These provide protection to both the machine and operator.

4. Connect motor cables to motor drive. 5. Connect emergency stop switch. 6. Connect limit/home switches.

MomusDesign

2. Determine locations of components in electronics bay. BENCHTOP CNC ROUTER PLANS

A brief installation overview of two popular drive boards will be covered here. However, this should be used as REFERENCE ONLY, and the manufacturer's installation instructions should be considered the definitive documentation for wiring. The two drives covered here will be the Xylotex and the Gecko G540. Wiring diagrams are given for each, including emergency stop switches and limit switches. There are often multiple methods of configuring these switches, so again these diagrams should be used as reference, and considered supplemental to the documentation provided by the manufacturer.

7. Firmly fasten all components in place.


installation of electronics

page

142

It can be helpful to install the electronics on the machine before making its final mechanical adjustments. This will allow easily jogging the machine into multiple positions with the computer, which will especially be helpful on the Z axis. The exact wiring procedure will depend on the particular motor drive(s) and other components being used. Also, if electronics components are purchased as a kit, much of the wiring may already be done, using pre‐installed connectors, resulting in a nearly “plug and play” system. This section will illustrate the general routing of cables on the machine.


MomusDesign

The cable arms provide a means of organizing the cables that run to the gantry, and control how they are flexed as the machine travels. Route the wiring for the Y and Z stepper motors as shown in the photos. Simple cable ties are used to secure them to the cable arms. Be sure that there is no way that the cables can hook anything or bind as the gantry and carriage move through their full range of motions. Be sure to provide enough cable length on all 3 stepper motors to adequately reach the location of the drive board, without being pulled taut. The power cable for the router, and limit switch wiring can also be run along the cable arms. Try to maintain as much distance between each of these parallel cables as possible to prevent transference of electrical signal noise. The vertical threaded rods on the cable plate and the center of the gantry may be used for cable attachment. It may be found that the cabling flexes more smoothly without fastening it to the rod on the gantry. If this rod is not used, cut it down shorter, so that cables can not get caught on it.

In the image to the left, the location where the drive board will be mounted has been marked. It will be mounted on the four nylon stand‐offs that are next to the screws. An awl was used to create a pilot hole, and the mounting screws were fully threaded into position without the board present. This will form threads into the wood, which will allow a more careful feel for how tight they are when installing the board. This can help avoid over‐tightening, putting too much pressure against the board. This also prevents having to put a lot of pressure on the screwdriver, which could cause it to slip off and damage the board.


wiring the machine

page

143

There are multiple types of cable which are advertised for use on CNC machines, and not all are equal in performance. Three types are shown in the image to the right. There are several attributes that are important to consider for machine wiring. The first is the flexibility of the cable. As the machine moves through a range of motion, the cables must flex to accommodate that movement. There are different flexibility ratings available. All three cables to the left are advertised as “flexible,” however, only the one on the far right is classified as “continuously flexible” and is rated for millions of movement cycles. Its large diameter is due to a thick silicone rubber casing. It can also be seen that this cable has a high number of very fine wire strands, rather than a few thick, stiff strands which will fatigue quickly. The other two cables are only “flexible” in that they can be flexed into position during a wiring installation. They are not intended to be subjected to flexing during service. If continuously flexed they may break. This is crucial, as many types of drives will be destroyed if a wire breaks while it is under power.


MomusDesign

The other cable feature seen here is shielding. Shielding provides a way to neutralize electrical noise, which may cause problems with motor operation, or false limit switch signals being sent to the control software. Wires may be twisted in pairs, which also helps to neutralize noise signals. The cable on the far left is unshielded. The middle one uses a thin metalized mylar strip. The right one uses a heavy stainless steel braiding. When installed on a machine, this shielding “tap” that runs through the cable will be connected to ground.

Some method should be used to provide a seal where the cables enter the machine housing. Without this, dust will be able to enter the electronics bay. The cables should also be secured in some manner, so that they cannot accidentally be pulled through the hole. The plugs shown here, in the images to the right, were milled from 3/4” MDF, and were the first parts to be cut on the finished machine. The cutting of these parts can be seen on page 168. They fit by a light press fit, and were tapped into place with a mallet. They grip the cables tightly, preventing any movement.


cables

page

144

wiring diagram for XYLOTEX 3 axis board to X motor

to Y motor

to Z motor NOTE: Color of motor wiring may vary, depending on manufacturer.

24 volt power supply

XB#

XB

XA# XA

YB#

YB

YA#

YA

ZB#

ZB

ZA#

NOTE: All limit switches and emergency stop switch to be wired NC (normally closed.)

ZA

P13 P11 P1 10K

10K

10K

P16 GND

Y limit

P17

VCC

TPZ

GND VBB

P15

Z limit

TPY

VBB GND

MS1 MS2 ENA# X AXIS

X limit

TPX

MS1 MS2 ENA# X AXIS

10K

MS1 MS2 ENA# X AXIS

Y limit

X limit

P14

GND VCC

GND DIR_A STEP_A VCC

ENAX ENAY ENAZ GND

GND

24v cooling fan

emergency stop switch


P12

MomusDesign

P10


to electrical outlet electronics‐ Xylotex wiring diagram

page

145

INSTALLATION OF XYLOTEX DRIVE Wire the power supply to the drive board. This is best done off the machine at first, as the board requires adjustments to be made to it. The Xylotex requires setting the individual output voltage for each motor axis. This can allow use of motors with different power requirements on each axis. This adjustment is done with only the power supply hooked up, NOT THE MOTORS, and using a digital multimeter (left photo). A small potentiometer is turned to achieve the desired output voltage. Consult the Xylotex documentation for your board to determine the voltage value that is required. Be sure to not exceed the maximum voltage specified, as damage to the board can occur. With this "Vref" voltage set for each axis, the board can be wired to the motors (right image).


MomusDesign

In the image to the right, the drive board is mounted and wired to the power supply and motors. The power cord for the power supply enters from the right, and is routed up over the board and into to the left side of the space. Notice it is knotted to prevent it from being pulled through the hole. When using this board at its higher range of possible voltage outputs, a cooling fan is required. Here a small fan is mounted to a small piece of paper mat‐board, which is held in position with small wood screws. The fan is powered by the drive board itself, and is positioned where it will blow air over the heat sinks on the board.

A couple of small pieces of wood blocking were attached to the top surface of the electronics bay. The power supply was attached to this, essentially "hanging" from the top. This put it in a convenient orientation to run all of the wiring. Plan your layout carefully so that wiring is neat and is easily traceable. More wiring will be added later for an emergency stop button and axis limit switches, so plan for this wiring as well.


electronics installation‐ Xylotex

page

146

wiring diagram for Gecko G540 drive board

to electrical outlet

Z AXIS

A 9

B

A

5

9

4 8 3 7 2 6 1

A AXIS

TRIM

R

B

TRIM A

5

4 8 3 7 2 6 1

9

B

STP = DB25 P4 STP = DB25 P5


A

5

9

4 8 3 7 2 6 1

R

TRIM

R

B


5

4 8 3 7 2 6 1

R


PARALLEL PORT ON

POWER

CHARGE PUMP

FAULT

24 volt power supply

OFF

1

X limit

3

4

5

6

7

8

9

10

11

12

X limit

Y limit

Y limit

Z limit ‐VDC

2

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Y AXIS TRIM


X AXIS

emergency stop switch

+VDC


electronics‐ Gecko G540 diagram

page

147

INSTALLATION OF THE GECKO G‐540 DRIVE If operating the Gecko G540 drive with supply voltage and output currents that are near the high end of its capacity, heatsinks should be installed to reduce operating temperatures. The heatsinks being installed here were purchased as a kit from Soigeneris, and are intended specifically for use on this drive. It supplies three individual heat sinks, which are attached with included double sided tape.


MomusDesign

The mating surfaces of the heatsinks and the bottom of the drive should be cleaned with rubbing alcohol before installation. Carefully apply the tape to the bottom of the drive. As seen in the image to the right, holes were cut in the tape at locations of subtly protruding screws, to allow the heatsinks to sit as flush to the surface as possible.

Carefully position and adhere the heatsinks into position on the bottom of the drive. In addition to the heatsinks, a fan can also be used to further reduce drive temperatures.


electronics‐ Gecko G540 installation

page

148

XA

resistor value = motor current rating x 1000

XA# XB XB#

The Gecko G‐540 drive requires installation of a 1/4 watt, 5% resistor in the wiring to each motor, to properly control the amount of current that is supplied to that axis. As per the Gecko documentation, this resistor is installed at the drive end of the motor wiring, within the DB‐9 connector backshell. The value of this resistor can be found by multiplying the motor current (up to 3.5 amps) x 1000. Thus, for a 2.5 amp motor, the proper resistor would be 2.5K ohm, 5%, 1/4 watt.

Typical Gecko G540 bipolar motor wiring.

MomusDesign

There are a couple of alternatives to installing this resistor. One is to purchase a G‐540 kit from a supplier who incorporates the proper resistor directly into molded wiring for their motors. This avoids hand soldering motor supply wiring and sourcing the proper resistor. It results in a system that is very convenient to assemble, being nearly “plug‐and‐play”.


to X motor

NOTE: Color of motor wiring may vary, depending on manufacturer.

Another alternative, if soldering your own motor cables, is to use a Soigeneris EZ‐G540. This component, which is shown in the three images to the right, incorporates an adjustable potentiometer into a DB‐9 backshell. By using this device, it eliminates soldering a separate resistor. It also provides large solder pads for the motor wiring, making soldering easier than within a standard DB‐9 connector. Once installed, the potentiometer is adjusted to set the proper resistance value. A digital multi‐meter must be used to measure this setting.


electronics‐ Gecko G540 motor wiring

page

149

With the proper resistor installed in the motor cables, they can be installed on the machine, as per page 143. In the image to the right they are seen extending into the electronics bay. Also seen in this image is that the location of the drive board has been determined, and mounting screws with nylon standoffs have been installed.

In the image to the right, the power supply has been placed in the electronics bay. It is not yet fastened in place, allowing movement for ease of making wiring connections. Its leads are routed to the position of the drive board.


MomusDesign

One end of the wiring from an emergency stop switch has also been connected to the power supply ground, and is placed in position to be connected to the drive. The first connection to the drive that should be made is to connect only the power supply. Connect the positive lead to terminal 11 and the negative lead to terminal 12. With the power supply connected, turn it on, and the red LED on the board should illuminate, as seen in the image to the lower left. After verifying that the red LED illuminates, turn off the power supply. Connect the lead from the emergency stop switch to terminal 10. This switch should be wired normally closed. As per the Gecko instructions, disable the charge pump switch. Turn on the power supply, and the green LED on the drive should illuminate. Turn off the power again and attach the motor cable DB‐9 connectors to the drive. The system should now be operational. Connect a DB‐25 cable to the PC parallel port, and check that the machine can be jogged through each axis by using the machine control software. The final installation step is to adjust the trimpot of each axis on the drive. Consult the Gecko documentation for this procedure. It is most easily accomplished with the motors disconnected from the belts/leadscrew. To keep the motors turning at the desired rpm for tuning, a short G‐code program can be written, or the jogging speed adjusted.


electronics‐ Gecko G540 installation

page

150

X home

Y home

Z home

MOTOR DRIVE

P10

X limit

Y limit

Z limit

GND

Regardless of type of motor drive used, the system should be installed with limit switches. These are small microswitches installed just before the end of travel on each axis. When the machine reaches this point in travel, the switch is triggered, sending a signal to the machine control software, which stops motion. This prevents the machine from accidentally slamming into the end of its travel, potentially causing damage or operator injury.

NOTE: Diagrams represent input logic only, they are not wiring diagrams for any specific drive. Particular drives may require resistors at each switch input. Consult documentation from drive manufacturer for requirements.

In addition to adding a level of safety, they can also be used to “home” the machine. Each time the machine is turned on, the machine control software can be instructed to “home all axes.” The software will sequentially move each axis of the machine in a desired homing direction, until it triggers a switch. It will then back off the switch a small amount so that it is no longer triggered. The software will consider this the zero coordinate “home” position for the axis. This will provide a consistent 0,0,0 starting position each time the machine is used. The software will now know where the tool is positioned in space. X home

Y limit

Z limit

P10

Y home P10

Having consistent 0,0,0 machine coordinates that are found through homing allows use of “soft limits.” These are travel limits that are set through the software, that prevent the machine from traveling as far as a limit switch during operation. This will be discussed more fully in the section on Mach3 setup.

MOTOR DRIVE

P13 Y home

Z home

Limit switches can be installed in many wiring configurations. Generally speaking, a compromise must be found between giving the software as much knowledge of machine position as possible, while not using an excessive number of parallel port input pins. The diagrams on this page illustrate some of the potential configurations for wiring the same number of switches.

GND

X home

X limit

P12 P13

Y limit

Z limit

At one extreme, all switches can be wired through a single pin. No matter which switch is activated, motion will be stopped. However, the software will have no way of determining which switch was triggered. Correct machine homing can still be done, as the software knows which axis it is putting into motion.

Y home

Y limit

Z home

Z limit

At the other extreme, each switch is wired to a separate pin. This gives the software the maximum knowledge of which switch is triggered. However, it requires more input pins than are typically available, in addition to a large amount of wiring.

X home

X limit

Y home

Y limit

The diagram in the lower right was used on this machine. It is considered a good compromise between maximizing software knowledge while minimizing input pins. Note that limit switches are always installed normally closed, so that any breakage of wiring will stop the machine. Also note that a switch in the Z‐ direction is not used. Due to the variability of tool lengths, it is more practical to control motion in this direction through soft limits.

P11 P12 MOTOR DRIVE

MOTOR DRIVE

P15

P10

P11

GND

X limit

P14

GND

P10 P12

MomusDesign

X home

MOTOR DRIVE

P12

Z home

P11

P11


X limit

Note that this 0,0,0 machine coordinate does not have to be considered as the 0,0,0 position on a part when running a job. A separate 0,0,0 work origin point can be set for each job. This exists independently of the machine coordinates, which will always have 0,0,0 in the same position.

Z home

version 2.1 copyright 2013 GND

electronics‐ limit switches

page

151

pin 10 pin 11 pin 12

X limit

MOTOR DRIVE

X home

to Y and Z axis limit switches

The image to the right shows this wiring as it was applied to a Gecko G540 drive. Note that this cable is shielded, and the tap is also connected to the ground point. The coil of single wire in the center will be used for the X axis limit switches. to ground

4 conductor cable Z home Y home

In the image to the right, all of the limit switch wiring is connected to the Gecko drive, as well as grounded to the power supply. With all of the connections made, the drive is secured in position on the nylon standoffs.

MomusDesign

Y limit

to pin 12 to pin 11


GND

A single, 4 conductor cable can be used to wire the limit switches for the Z and Y axes. A general diagram of this configuration is shown to the left. Note that some drives, such as the Xylotex, may require resistors at each switch input pin.

Wiring was soldered to the microswitch connectors before attaching them to their mounting brackets, as seen to the left. Be sure to connect the wiring to the correct lugs, so that the switch will be operating in the normally closed configuration. The switches are next installed on the machine. The image to the right shows the front X axis switch, which is triggered by the extended length of threaded rod. A small hole is drilled to route the wiring directly into the electronics bay.



page

152

The X axis limit switches are mounted as seen in the images to the left and right. The brackets were attached to the base with screws. A stack of washers is used as a spacer between the bracket and base, with the switch sitting tightly to the surface of the base skin. Install the switches in a position where they are triggered by the extended length of threaded rod. Install the mounting screws so that there is some amount of adjustability to the brackets. The switches should be able to be adjusted so that they trigger about 1/4” away from any hard collision at the end of the axis travel.


MomusDesign

The single Z axis switch is mounted as in the image to the right. It is also triggered by an extended length of threaded rod. Washers were used behind the bracket, to provide clearance for the heads of the screws that attach the switch to the bracket. Mounting the Y switches on the gantry requires drilling and tapping #10‐32 holes in the gantry tube, as seen in the image to the left. Carefully determine the placement of the switches before drilling. Note that the Y switches are triggered by the outermost carriage bearings.

The images to the left and right illustrate the installed Y axis switches. Washers were again used between bracket and gantry to provide clearance for screw heads. Wiring was fastened to the gantry with strips of electrical tape. With all switches, make sure that the connectors cannot possibly ground to any part of the machine, as this will interfere with their proper operation.



page

153

A side door may be provided to cover the electronics bay. This is also a convenient surface for mounting an emergency stop switch. A door can be fabricated from any flat material. Due to this, the material for the door has not been included in the Bill of Materials. The door shown here was cut from a piece of polycarbonate sheet, which was sanded on both sides with fine sandpaper to give it a frosted appearance. The only limitation on door material is that it should be able to withstand the force of hitting the emergency‐stop switch if it is mounted here.


MomusDesign

The hole for the emergency stop switch was cut by stitch drilling and filing. The same technique was used to cut a hole for mounting the input cable for the electronics. A series of holes were also drilled to provide airflow for the power supply fan, and a cooling fan that will blow air across the drive board.

The door was mounted with two 1 1/2” utility hinges and two magnetic latches. A length of wood was screwed to the door to provide a handle, and to stiffen the edge of the thin material.


side door

page

154

Basic software configuration will allow use of the computer to jog the machine during alignment, and provide preparation for the first use of the machine. Setup of Mach3 software is shown here, although many basic concepts will apply to other applications, such as EMC2. Extensive documentation is provided by the software developers, and it should be followed closely. The setup shown here should be considered as supplemental reference, and is no way intended to provide the full knowledge necessary to use the software. If you haven't already, install the software per the developer's directions. This may involve rebooting the computer and running a program to test the operation of the parallel port. Some manufacturers of motor drives will also provide a Mach3 .xml file, which creates a “profile” that has numerous settings preconfigured for the particular drive. Gecko is one such manufacturer, which provides a .xml file for its G540 drive. If an .xml file is available for your drive, install it in the Mach3 install folder.


MomusDesign

Parallel Port settings: Config>Ports and Pins>Port Setup and Axis Selection (upper right image) This screen is used to activate the correct port. Consulting the Windows Device Manager may be necessary to determine the port address. The other setting on this screen is for Kernel Speed. This setting determines the frequency of the output pulse rate. A higher pulse rate translates to higher motor rpm. For typical stepper motor systems, 25,000Hz is adequate. Config>Ports and Pins>Motor Outputs (middle right image) The motor wiring must be configured to correspond to specific parallel port pins to receive proper output signals. Consult motor drive documentation for this information. If using a drive‐ specific .xml file this should already be set.

Jogging: On most screens within Mach3, the arrow keys and PgUp/PgDn can be used to jog the 3 axes. This function may need to be configured by going to Config>System Hotkeys. In addition to using keyboard input, the Manual Pulse Generator fly‐out may be used. Pressing the tab key makes this screen appear, and gives increased functionality for jogging. This can be used for continuous jogging, or by discrete steps. Do not use the jogging function until the correct motor settings have been entered (following page.)


Mach3 setup

page

155

Motor Tuning: Config>Motor Tuning> desired axis The software must know how many step pulses must be sent to the motors to result in machine movement of one unit (inch or mm.) For the X and Y axis belt drives: Motor steps per revolution =200 Timing belt pitch (.200”) x teeth on pulley (10) = 2.00” per rev. Microstepping value (Gecko G540 = 10x) One motor revolution (200 steps) = 2.00” of movement. Thus 100 motor steps = 1 inch of travel. However, since the motor drive has a microstepping feature, this results in a higher number of steps per revolution. Thus, for a 10x microstepping drive, 10x microstepping X 100 steps/inch = 1000 steps/inch. For this drive, 1000 steps/inch will be the value entered in the X and Y axis fields titled “Steps per.”


MomusDesign

For the Z motor axis, the factors are: Motor steps per revolution =200 Leadscrew pitch (1/8” x 4 start acme) = .50”” per revolution. Microstepping value (Gecko G540 = 10x) One motor revolution (200 steps) = .50” of movement. Thus it requires 2 revolutions of the motor shaft to cause one inch of movement, or 200 steps X 4 revolutions = 400 steps/inch. Factoring the microstepping feature, this again results in a higher number of steps per revolution. Thus, for a 10x microstepping drive, 10x microstepping X 400 steps/inch = 4000 steps/inch. For this drive and particular leadscrew pitch, 4000 steps/inch will be the value entered in the Z axis field titled “Steps per.”

Velocity: This sets the maximum speed, which is used during jogging or rapid moves. This may be limited by the particular electronics being used, but in general the machine is capable of very high speeds. This should be kept to a reasonable speed to avoid the machine moving faster than the operator's response time to hit the emergency stop switch.

version 2.1

Acceleration: This sets the acceleration and deceleration of the motors. This should also be kept to a reasonable value, as stepper motors can become generators under deceleration. This can feed excessive voltage back to the drive, potentially causing damage.

copyright 2013

Mach3 setup

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156

Limit Switch Inputs: Config>Ports and Pins>Input Signals The software must be configured to know when a limit switch is being activated, as well as knowing on which axis the event is occurring. The image to the right shows typical settings that correspond to the wiring diagram used on pages 151/152. The port# must correspond to which parallel port is being used to control the drive. The pin number corresponds to how the limit switches are wired through the drive (or breakout board.) On the Gecko G540 and Xylotex drives, certain terminal connections correspond to certain parallel port pin numbers.

Home Referencing: Config>Homing/Limits


MomusDesign

The machine can be instructed to sequentially move each axis in a determined direction, until it hits a “home” switch. The limit switches, configured above, can also be used for this homing operation. No separate switches are required. By checking “auto zero”, as seen in the image to the right, an axis will be included in the homing operation. The X and Y axes are typically homed in the negative direction, while the Z is homed positive. Due to the particular motor wiring, here it can be seen that the direction of two motors required reversing, in order to orient the correct positive/negative movement directions. Activating the REF ALL HOME command (circled in red in the lower right illustration), each axis will move at a reduced speed until it contacts a home switch. It will then back away from the home switch slightly. This position will be the zero coordinate for the axis. These three 0,0,0 locations set the “machine coordinates.” Soft limits: Config>Homing/Limits Rather than depend on limit switches for end of axis protection, travel limits can be set through the software. These are distances from the 0,0,0 machine coordinates. The advantage of using soft limits is that the machine will gently decelerate as it approaches this travel limit, unlike the abrupt stop caused by hitting a limit switch.


Mach3 setup

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eq ua l

l ua eq

At this point the machine is basically finished and primarily needs alignment before use. The first alignment step will be to get the two X rails exactly parallel to the surface of the machine bed. This is done by measuring up from the bed at the front and rear of each rail, and adjusting them so that the measurements are equal. This can be accomplished to a high level of accuracy with some relatively simple tools.


MomusDesign

The image to the left illustrates an adjustable height gauge that was constructed from some scrap rectangular tubing and a length of threaded rod. The tubing size was 1 1/2" x 2". The surfaces of the tubing are very flat and allow the gauge to sit flush against the bed without rocking. The top of the threaded rod was filed to a shallow point. Note in the images to the right that the threaded rod was bent very slightly to the side so that it would reach exactly under the rails.

The height gauge is used in conjunction with a set of feeler gauges (middle left image.) These are simply thin flexible metal strips that are inserted into a gap to "feel" how wide it is. They can be purchased at any auto parts store for a few dollars. Adjust the threaded rod up under the front of the right X rail until it is almost touching. Ideally, leave about .010" of clearance. Use the feeler gauges to measure this gap. With trial and error, find the feeler gauge strip, or combination of strips together, that slides into the gap with just a faint amount of drag along its surface. Without changing its adjustment, reposition the height gauge under the rear of the right rail. Measure the gap between it and the rail with the feeler gauges. Loosen the bolts holding the rail to the rail angle and reposition it so that the gap is the same at the front and rear. This may take moving the height gauge from front to back several times and taking repeated measurements. With some patience, the rails can be very accurately positioned this way. Do the same for the left rail. The right and left rail should each be the same exact same height above the bed.


alignment

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The two X rails should now both be parallel to the machine bed. The next adjustment is to set the Y rail parallel to the bed. This is done in a similar fashion, but we will now be adjusting bearings to effect its height. We will again be using the height gauge and feeler gauges, this time to measure the left and right sides of the Y rail (left and right images.)


MomusDesign

The four bearings that ride along the tops of the X rails will need to be adjusted (circled in the middle right image). All four will need to be exerting equal pressure downward on the rails so that the gantry will not rock. Again, this will require some trial and error and multiple repositioning of the measuring gauge during the process. Tighten the nuts on the bearing bolts so that they are just slightly snug and then adjust the set screw to reposition it before fully tightening the nut (lower right image).

While adjusting these four bearings to get the Y rail parallel to the bed, occasionally check that the front face of the Y rail is as close to perpendicular to the bed as possible (left photo). The closer to perpendicular, the easier it will be to adjust the Z axis later. Take your time with these adjustments and be patient. It may take multiple attempts to get the adjustment correct and may be frustrating and time consuming at first. The process will proceed faster as you develop a feel for adjusting the bearings.


alignment

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Once you are satisfied with the adjustment of the four bearings that ride along the tops of the rails, next adjust the four that ride along the lower edge. Move the gantry so that the bearings line up with the four depressions in the inner skins, as shown in the lower right image. These are provided to allow clearance to get a wrench onto the heads of the bolts. However, as the bolt heads are thinner than normal, it will take a special wrench to fit onto them.


MomusDesign

There are a couple of solutions to this. One is to simply grind down the head of a standard wrench so that it fits. If you do this, grind the wrench slowly to avoid overheating the metal. Cool it often by dipping it into water. Another solution is to use a ready made wrench. Many power tools have special wrenches to fit their arbors that are thin. The lower left images shows a wrench for a router that was the required 1/2" size. Another option is to buy a bicycle “cone wrench” that is made for working on bicycle hubs (wrench with blue handle in image.) Buy one in a 13mm size. Note that this is a slightly loose fit on the 1/2" head (which is 12.7mm) but should work fine. These do not need to be excessively tightened, so no rounding should occur if the wrench is squarely on the bolt head.

Adjust these four bearings until they lightly touch the bottom edge of the rails. This also requires acquiring a feel for how tight against the rail they need to be. They need to be tight enough that there is no free play, but not so tight that they increase rolling resistance. A good test is that with the gantry stationary, you should still be able to grasp the bearing and turn it against the rail. It should slip against the rail when turned with some pressure. It should not slip very easily, but should not turn completely freely either. The tendency while adjusting may be to over‐tighten the bearings. It is easy to over‐tighten the bearings to the point where the stepper motors can not move the machine, or lose steps during movement. If in doubt, it is better to go with an adjustment that seems slightly too loose rather than too tight.


alignment

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Most of the bearings on the machine are adjusted in sets, that simultaneously touch opposing sides of a rail. This may either be across the width (left illustration), or across the thickness (right illustration). Keeping this in mind can help during adjustments, as there are a couple of strategies that can be used to cause an adjustment to have the needed effect. Adjusting two bearings along one surface (the top two bearings in the upper left illustration) can cause either rotational shift or a parallel shift. Make these adjustments with the opposing bearings loose. Once bearings along one surface are satisfactory, adjust in the opposing set (middle left illustration.)


MomusDesign

If all four bearings are making the desired amount of contact, a rotational shift can be accomplished by leaving two opposing ones alone, while adjusting the other two equal amounts in the same direction. (lower left illustration.)

The next bearings to adjust will be the carriage bearings that ride along the Y rail. First adjust the four that contact the top and bottom edges (circled in the middle right image.) While adjusting these four bearings, also try to get the carriage itself perpendicular to the bed, as shown in the photo to the right. The closer to perpendicular the carriage can be set, the easier the alignment of the Z axis rail and Z screw will be later.


alignment

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The Y axis bearings that ride along the front and rear faces of the rail are adjusted next. There are a total of eight bearings, that need to be adjusted as one group. Note that on the front ones, a single socket head cap screw secures two bearings at a time. Each bearing does have an individual set screw adjuster. You may find it easiest to adjust these double sets of bearings first (middle right image), and then adjust the rear ones in to touch the rail (upper right image.)


MomusDesign

The rear bearings also use bolts with thinner heads for clearance, so the thin wrench will be needed here too.

Like with the previous adjustment, check often during this adjustment to try and set the carriage perpendicular to the bed in the front/rear direction. Again, this will make later Z axis adjustments much easier, and will result in smoother Z axis operation.


alignment

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The next adjustment will be to the Z axis rail. This needs to be adjusted so that it is perpendicular to the machine bed in both side to side, and front/rear directions. First adjust it side to side, using the four bearings circled to the right.


MomusDesign

Jog the Z axis down so that it is at the lowest point of its travel. Be careful that the rail does not move low enough that it it no longer captured between the top bearings. A small triangle or square can now be used as a gauge to set the rail perpendicular. When the Z rail is perpendicular to the bed, double check by flipping the triangle around and holding it up to the other side. If your triangle is not exactly a 90 degree angle, or the bed surface is uneven, then flipping the triangle to the other side will reveal the discrepancy, and that something is inaccurate.

Move the triangle or square to the front of the rail as shown in the image to the right. Adjust the eight bearings that ride along the front/rear surfaces of the rail to get it perpendicular to the bed. These also have paired bearings on long socket head cap screws, so use the technique that was used on the Y rail. All three of the machine axes should now be in proper adjustment and alignment.


alignment

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The final adjustment is to the Z axis drive screw. There is no simple place to directly measure to find its proper positioning, so it will take some trial and error. Begin by jogging the Z axis to its lowest position. Tighten the #4‐40 x 1" machine screws and nuts holding the anti‐backlash nut so that they are snug enough to hold it in position, but it can still be repositioned with some slight force. Also snugly tighten the nuts securing the nut plate, and nut plate block. Each of these points can later provide adjustability. Standing in front of the machine, visually align the drive screw so that it is parallel to the Z axis rail. Move to the side of the machine and do the same in that direction.


MomusDesign

Jog the machine all the way to the top of its Z axis travel. It should not bind, and the sound from the stepper motors should stay consistent during the travel. Readjust as necessary. It will probably require jogging the Z axis up and down several times, readjusting each time, to finally get it correct. Once it is in a satisfactory position, tighten all of the nuts fully. On the anti‐backlash nut, be sure to either use thread‐locking compound (the removable type), lock nuts, or lock washers. These are highly vulnerable to vibrating loose, and their small size does not allow excessive tightening without stripping threads.

If all is adjusted correctly, the Z leadscrew should be parallel to the Z rail when viewed both from the front and from the side. They should remain parallel in both directions as the Z axis is jogged along its length. Binding may occur if the two are not parallel during the entire length of travel.


alignment‐ Z screw

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Install the router mounts, as seen in the image to the left. Note that the mounts shown in this series of images are an older variation, and are not exactly the same shape as the current design. With the Z axis jogged to its lowest position, set a triangle or square against the faces that will contact the router body. Note if the square touches both evenly. If the mounts are not exactly perpendicular to the machine bed they can be shimmed into the correct position. Thin metal foil or paper can be used as shim stock.


MomusDesign

When satisfied that all of the clamping surfaces are perpendicular to the bed, install the router and front clamp halves. Tighten to secure the router.

Make sure that the router and cord clear all mechanical components as the Z axis moves through its full range of motion. The extended threaded rod that contacts the Z axis limit switch can also be used to manage the router cord. Be sure that it can not interfere with proper operation of the limit switch. Here a washer and nut were used to contain the cord.


router and mounts

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Some method is required to secure workpieces to the bed area. The bed area should also be provided with a sacrificial “spoilboard” wear surface that can accommodate milling operations that cut through the entire thickness of the work. The spoilboard may be as simple as a piece of medium density fiberboard (MDF) that is fastened to the machine bed. Workpieces can in turn be screwed to this surface. A more versatile system is shown here, which consists of aluminum T‐track extrusions that are set within pieces of MDF. This provides a convenient and fast method of clamping that does not require sinking screws into the spoilboard surface. Many types of clamping accessories are commercially available for T‐track systems.


MomusDesign

The assembled pieces in the illustration to the left result in a working surface that measures 15” x 15”. This size will allow the cutting tool to just extend beyond each edge. This is necessary so that the router can be used to mill this surface flat after installation. The spoilboard can also be resurfaced after it wears during use. The assembly shown here used a piece of 3/4” plywood as the center layer. This was used rather than MDF as it is easier to screw into. Any screw that penetrates into MDF should be provided with a pilot hole to avoid damage, as the MDF does not easily displace material. The top MDF strips were fastened from the bottom, through countersunk clearance holes in the plywood layer. 1.500

.75

1.000

.50

1.000

.50

.75 1.500

.25 0.500

1.375 2.750

Typical extruded aluminum T‐slot track.

(2) pieces, MDF.

.75 1.5

.50 1

.25 0.5

2.75 5.500

.25 0.5

Thickness of spoilboard: The Z axis of the machine has a substantial amount of travel, and it should be kept in mind that the machine will be most rigid with the Z axis at its highest. Thus, it is beneficial to mount the workpiece as high as possible. If you anticipate cutting a consistent type of parts, such as mostly parts cut from 3/4” thick wood, then the spoilboard can be constructed with this in mind. It can be built to a thickness that raises the work to a desired height. The spoilboard could also be constructed in multiple layers, that could be removed to lower it when necessary.


(4) pieces, MDF.

spoilboard

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The middle right image illustrates the finished spoilboard before mounting on the machine. Note that the top of the MDF surface is well above the top surface of the aluminum T‐track. This provides a safe thickness of wear surface that would need to be penetrated before the cutter would contact the metal track.


MomusDesign

The lower left image shows one type of clamp that is available for this T‐track system. Special T‐track bolts are also available, allowing more custom clamping configurations. It is recommended to use clamp components that are made of plastic, brass, or other soft metals where possible. This will reduce the danger that is possible if a clamp is accidentally hit by a cutting tool.

In the image to the right, the finished spoilboard is mounted on the machine bed. It was carefully located so that the cutting tool can cut move just beyond its perimeter for surfacing. It was also carefully positioned so that the T‐slots are as parallel to the X axis travel as possible. This makes it easier to clamp material to the spoilboard in a position that is known to be parallel to that axis.


spoilboard

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Congratulations, the machine is now complete and ready to be used. After familiarizing yourself with a CAM application, and generating G‐code to cut a part, here is a suggested procedure for the first use of the machine. 1. Home the machine by using the Mach3 REF ALL HOME command. This will zero the Machine Coordinates. 2. Jog the machine so that the tip of the tool is in the location on the workpiece that corresponds to 0,0,0 as it was defined in the CAM software. When in that position, use the buttons circled in the image to the left to set the Work Coordinates. Note that this does not alter the Machine Coordinates, which are still used to control soft limit locations. 3. Jog the machine to make sure that soft limits are functioning correctly. The Soft Limits button (also circled in the left image) in Mach3 needs to be activated, which will be indicated by a green border around the button.


MomusDesign

4. Load a G‐code program. File>Load G‐code. The lines of code will appear in the window that is circled in the right image. 5. Run the program. For the first time running a program it is advisable to zero the Work Coordinate for the Z axis higher than the workpiece. This way you will be “cutting air” and have an opportunity to observe if the program seems to be running correctly. Keep a hand on the emergency‐stop button and click the Cycle Start button in Mach3 (also circled in the right image.) Watch to see that the axes appear to be traveling the correct distance. If there are any problems, the machine can be stopped by hitting the emergency‐stop button, or the red Stop button in Mach3 (circled at right.) 6. If all appears to be working correctly, set the correct Z axis Work Coordinate, jog the tool a safe distance above the workpiece, turn on the router spindle, and run the program. Congratulations again, you've just cut your first part. 7. It is advisable to measure the finished part, to compare its cut dimensions to its design dimensions. If there is any variation, the steps per inch values in the Mach3 motor tuning screens may need slight adjustment.

version 2.1

This concludes the building of the machine, and hopefully begins many enjoyable hours of machining parts. Be creative!

copyright 2013

‐Bob Pavlik [email protected]

first use

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SUPPLIERS Metals

Stepper Motor Drives

Epoxy

Online Metals 1138 West Ewing Seattle, WA 98119 800_704_2157 http://www.onlinemetals.com/ [email protected]

Xylotex, Inc. 2626 Lavery Court #307 Newbury Park, CA 91320 http://www.xylotex.com/ [email protected] http://groups.yahoo.com/group/Xylotex/

Jamestown Distributors 17 Peckham Drive Bristol, RI 02809 http://www.jamestowndistributors.com/ ‐MAS low viscosity epoxy

Speedy Metals locations in Wisconsin, Michigan, Texas http://www.speedymetals.com/

GeckoDrive Motor Controls 14662 Franklin Ave. Suite E Tustin, CA 92780 http://www.geckodrive.com/ http://groups.yahoo.com/

Dumpster CNC http://dumpstercnc.com/ [email protected] ‐anti‐backlash nuts ‐motor couplings McMaster‐Carr http://www.mcmaster.com/ ‐precision acme threaded rod ‐many misc. components Stock Drive Products http://www.sdp‐si.com/ ‐drive belt ‐timing pulleys Bearings VXB Bearings http://www.vxb.com/ Ebay vendor user id: irvineman store name: VXB Bearings Skateboard and Slotcar

CNCrouterparts http://www.cncrouterparts.com/ ‐GeckoG540/motor kit with molded cables Longs Motor Ebay vendor user id: longsmotor99 store name: Changzhou Longs Motor Co ‐motors and drives. Ships from China. Soigeneris http://www.soigeneris.com/ ‐Gecko G540 drives ‐G540 heatsink kit ‐EZ‐G540 DB‐9 connectors with potentiometer

Bolt Depot www.boltdepot.com ‐hardware BOLT IT UP Ebay vendor user id: 5137jones store name: BOLT IT UP ‐hardware Multiple Items Hubbard CNC Ebay vendor user id: carolbrent store name: HUBBARD CNC INC ‐wide selection of CNC parts

NOTE: Momus Design has no affiliation with any of the vendors on this or the following page. Inclusion here does not necessarily imply an endorsement.

parts suppliers

MomusDesign

Power Transmission

KelingCNC/Automation Technology Automation Technology Inc 2112 Stonington Ave Hoffman Estates, IL 60169 http://www.kelinginc.com/ ‐vwide selection of motors and drives

Hardware


Metals Depot 4200 Revilo Road Winchester, KY 40391 http://www.metalsdepot.com/

Ebay vendor: user id: polymerproducts store name: Polymer Products ‐low viscosity resin


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SOFTWARE CAD (Computer Aided Design) Software

CAM (Computer Aided Manufacturing) Software

Machine Control Software

‐AutoCad ‐AutoCad LT ‐Inventor (3d CAD) AutoDesk http://usa.autodesk.com/

‐SheetCAM 2.5d CAM http://www.sheetcam.com/

‐Mach3 CNC controller ArtSoft Newfangled Solutions LLC http://www.machsupport.com/

‐Google SketchUp Free 3d modeler Google http://sketchup.google.com/ ‐Rhino3d 3d NURBS modeler McNeel North America http://www.rhino3d.com/ ‐Blender free 3d modeler, less intuitive than Rhino http://www.blender.org/ ‐SolidWorks (3D CAD) Dassault Systemes http://www.solidworks.com/

‐MeshCAM 3d CAM, with indexed 4th axis capability http://www.grzsoftware.com/landing/ ‐Cut2d (2.5d) ‐Cut 3d (3d) ‐VCarve Pro (V‐carving, 2.5d) ‐Photo VCarve (converts images to toolpaths) http://www.vectric.com/

‐CNC Lite ‐CNC Plus CamSoft (951) 674‐8100 http://www.cnccontrols.com/ ‐DeskCNC controller seriall port based controller IMService http://www.imsrv.com/deskcnc/

Misc. Software ‐FreeMILL (free basic 3d CAM) ‐VisualMill (3d) ‐RhinoCAM (plug‐in for Rhino3d) http://www.mecsoft.com/

‐Deskengrave (free) Converts TrueType fonts to .dxf drawings http://www.deskam.com/deskengrave.html

‐DeskProto Entry Edition simple 2.5d, 3d http://www.deskproto.com/

‐ACE converter (free) Converts .dxf drawings to G‐code http://www.dakeng.com/ace.html

‐ArtCAM Express 2.5d, 3d http://www.artcamexpress.com/

‐G‐code to .dxf converter (free) Converts G‐code to .dxf drawings http://www.cnczone.com/forums/ opensource_software/8814‐g‐code_dxf.html ‐LazyCAM (comes integrated into Mach3) Basic .dxf drawing to G‐code. http://www.machsupport.com/

MomusDesign

‐TurboCAD CAM plug‐in available IMSI/Design http://www.turbocad.com/

‐PhlatScript free 2.5d CAM plug‐in for SketchUp http://sketchuppluginreviews.com/2010/04/30/ phlatscript‐google‐sketchup‐plugin‐review/

‐LinuxCNC (EMC2) http://www.linuxcnc.org/


‐DoubleCAD XT Free AutoCad LT type clone, 2d. http://www.doublecad.com/

‐CamBam Plus 2.5d, limited 3d CAM http://www.cambam.info/


‐NCPlot (backplotter for G‐code verification) http://www.ncplot.com/

software suppliers

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Z axis thrust bearing addition:

# reqd. 1 1

BILL OF MATERIALS The materials for this upgrade are not included in the main Bill of Materials on page 27. These quantities should be added to that primary Bill of Materials when purchasing metal stock and hardware. Required is:

ALUMINUM .1875" x 2.50" x 2.25"

This addendum covers the installation of a pair of thrust bearing to the Z axis lead‐screw assembly. The original design of the Momus CNC router did not include a thrust bearing for several reasons: they would add to the overall cost of the machine, they add to the height of the Z axis while potentially reducing its travel, and require proper adjustment in order to be effective. A successful thrust bearing design would not only need to solve these issues, but in keeping with the rest of the design of the machine, would also need to able to be fabricated without special tools or equipment. However, there are several strong reasons for including such bearings. They relieve the stepper motor bearings of all axial force, which is beneficial as they have a low rating for loads of this type. Therefore, external thrust bearings will potentially increase the longevity of the Z axis stepper motor. The other reason is that a failure of the coupling between the motor and the lead‐screw could cause the router to plunge into the table. While this type of failure is unlikely, this thrust bearing upgrade will provide extra insurance against this happening.

ALUMINUM or hard plastic, such as ACETAL (delrin) .375" x 2.25" x 2.25"

BEARINGS (2) 3/8" x 13/16" x 9/64" unshielded needle bearings, VXB Item# Kit12703 (includes hardened washers) If ordering from a supplier other than VXB, be sure that the two hardened washers are included with bearings.

THREADED SHAFT COLLAR Delrin threaded collar to match lead‐screw pitch. Source: DumpsterCNC Alternatively, an unthreaded metal split shaft collar may be used. Hoever, this will be more difficult to adjust correctly.

Therefore, it is highly recommended that the following components be installed on Momus CNC routers. This upgrade is fully compatible with all previous versions of the machine. However, on machines constructed from older versions of the plans, it may reduce the Z axis travel by approximately 7/16", and will also raise the motor vertically by 3/8". This may cause cover interference on older machines that use quad‐stack stepper motors with a dual shaft. A thin shim between the cover and the machine base can be used to raise it for sufficient clearance. The assembly sequence shown here was photographed installing the parts onto an existing machine. The assembly sequence is identical on a new machine, only the gantry will not yet have been installed on the machine. Combine these instructions with those on pages 131‐132.

ADDENDUM z axis thrust bearings

MomusDesign

FABRICATED PARTS part # part name 46 thrust bearing plate 47 z axis motor spacer


LIST OF FABRICATED PARTS


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22 Z cable plate (existing)


MomusDesign

47 Z axis motor spacer

20 Z motor mount right (existing) 21 Z motor mount left (existing)

46 thrust bearing plate


ADDENDUM exploded view

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material: 6061‐T6 alum. 1.125 2.25

.928

.25 DIA., 4 holes .438 DIA.

.928

1.856


1.856

# required:

1

.75 1.5


MomusDesign

1.125 2.25

.928 1.856

2.25

.75 1.5

4.5

.928 1.856

.25 0.5

Slight enlargement of this notch may be necessary to allow proper adjustment of lead‐screw. 2.25 4.5

.1875 0.375


NOTE: Cut from 2.50" wide plate stock, as it is a more common stock size than 2.25"

ADDENDUM thrust bearing plate

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1.125 2.25

.928

material: 6061‐T6 alum. OR acetal plastic

.25 DIA., 4 holes


.928

1.856

1.856

1.50 DIA. # required: 1.125

1

2.25

.928


2.25

MomusDesign

1.856

.75

4.5

1.5

.928 1.856

.75 1.5

2.25 4.5

.375 0.75

version 2.1 NOTE: Cut from 2.50" wide plate stock, as it is a more common stock size than 2.25"

ADDENDUM z axis motor spacer

copyright 2013

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The images to the left and right show the additional lead‐ screw components that are not shown in the main plans.


MomusDesign

As shown to the left, thread the Delrin collar onto the leadscrew, about 1.5". Slide one unlubricated needle bearing, and its hardened washers, against the top of the collar. Insert this assembly through the hole in the aluminum thrust bearing plate (part #46). Slide the other unlubricated bearing and hardened washers onto the top of the plate.

As shown to the right, thread the motor coupler onto the end of the lead‐screw. Thread it down the screw until the end of the screw is aligned with the bottom of the slot in the coupler. Gently tighten the coupler in position.

As shown in the left image, thread the collar back up the lead‐ screw until it firmly compresses the stack of components against the coupler. While keeping it firmly threaded against the parts, tighten it in position.

Keep the collar tightened in place, and remove the other components from the lead‐screw, as shown to the right.


ADDENDUM thrust bearing assembly

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Thread the lead‐screw, with the collar installed per the instructions on the previous page, down through the anti‐ backlash nut, as seen in the image to the left. Thread it far enough that the top of the screw is approximately 1" below the bottom of the Z motor mounts. As seen to the right, lightly lubricate one of the needle bearings, and with it sandwiched between its hardened washers, slide it down the screw onto the collar. A light lithium grease can be used for lubricant. Be cautious to not use an excessive amount, that will get onto the surfaces of the collar. The collar should be kept clean.

As shown to the left, temporarily install the aluminum bearing plate with one or two of the 2.5" screws, and place the other lubricated bearing and washers on its top surface. Make sure its bore is aligned over the hole in the bearing plate.


MomusDesign

Raise the Z axis assembly up, so that the end of the lead‐screw is guided through the hole in the bearing plate, and through the bearing. While holding it in this position, thread the motor coupler onto the end of the screw. Thread it down the screw until it is firmly clamping the bearings and plate to the collar. This tightness is the pre‐load setting on the bearings, and should be tight enough to remove all slack. Maintain the coupler in this adjustment, and tighten its clamping screws.

Remove the temporary screws holding the bearing plate to the motor mounts.



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Set the new motor spacer (part #47) on top of the motor mounts.


MomusDesign

Set the cable plate (part #22) on top of the motor spacer. Place the stepper motor into position. Carefully raise the Z axis assembly up, so that the motor coupler is guided onto the end of the motor shaft. Be sure to carefully align the flat on the motor shaft with the set screw in the coupler (see page 131 for the addition of this set screw to the Delrin coupler.) It may take some wiggling to get the coupler to slide onto the shaft. Install the four screws that hold the motor to the mounts. Tighten them snugly in place.

Fully tighten the clamping screws on the coupler, so that the motor shaft is securely held. Tighten the set screw against the flat on the motor shaft. During the alignment procedure described on page 164, very slightly loosen the four screws holding the motor to its mounts so that the motor can be repositioned side to side for proper lead‐screw adjustment. Fully tighten the screws after this process. Do not loosen any of the clamping screws on the coupler or collar during this process, or the bearing pre‐load adjustment may be lost.



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The needle bearings that are used are an unshielded design, that must be protected against dust and cutting chips. The lower bearing can be protected by merely wrapping a length of PVC electrical tape around the circumference of the collar. Carefully set it so that it just lightly contacts the bottom surface of the bearing plate.


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The upper bearing can be protected by simply closing off the front of the cavity in which it sits between the motor mounts. This can also be done with tape, as shown to the right, or a blockoff plate can be fabricated.

After closing off the cavity, re‐install the Z axis limit switch. The limit switch placement will need to be adjusted from where it would be placed if no thrust bearings were used. This may mean only one screw will secure the bracket that is included with these plans.



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Momus Design Cnc Router Manual Version 2.1

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