FABRICATION OF MECHANICAL SCISSOR LIFT A Mini Project Report Submitted by
G Madhusudhan Rao
158W5A0315
SK.K.Khamuruddin
158W5A0324
K Naveen Teja
148W1A0386
B Anusha
158W5A0325
In partial fulfillment of the requirements For award of the degree of
BACHELOR OF TECHNOLOGY
With specialization in MECHANICAL ENGINEERING
Under the esteemed guidance of Mr. N Vijay Kumar, ME Associate Professor of ME Department
MECHANICAL ENGINEERING DEPARTMENT VELAGAPUDI RAMAKRISHNA SIDDHARTHA ENGINEERING COLLEGE VIJAYAWADA 520 007 OCTOBER 2017
DEPARTMENT OF MECHANICAL ENGINEERING 1
CERTIFICATE
This is to certify that the mini project titled “ FABRICATION OF MECHANICAL SCISSOR LIFT ” was
prepared
and
presented
by G
Madhusudhan
Rao(158W5A0315),
SK.K.Khamuruddin
(158W5A0324), K Naveen Teja (148W1A0386), B Anusha(158W5A0325) of B.Tech., 7th Semester,Mechanical Engineering in in partial fulfillment of requirements requirements for
award of the
Degree of Bachelor of Technology in Mechanical Engineering under the Jawaharlal Nehru Technological University Kakinada, Kakinada during the year 2017 -18
MINI PROJECT GUIDE
(N VIJAY KUMAR)
HEAD OF THE DEPARTMENT
(DR.N VIJAYA SAI)
2
Abstract
The following paper describes the information about fabrication of a simple mechanical scissor lift. Conventionally a scissor lift or jack is used for lifting heavy loads with less effort mainly in industries or any other fields where loads are lifted. It can be of mechanical, pneumatic or hydraulic type. The matter described in the paper is developed keeping in mind that the lift can be operated by mechanical means so that effort required to operate is less for lifting more weight. Also such design can make the lift more compact and much suitable for medium scale work. This paper also gives information on how scissor lift works with different means (exmechanical, pneumatic and hydraulic), basic information about worm and worm gear, rack and pinion, types of lifts, advantages of the scissor lift, different types of gears, gear nomenclature, threads and scissor arms
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FABRICATION OF MECHANICAL SCISSOR LIFT
1. INTRODUCTION
SIMPLE MACHINES
SCISSOR LIFT
TYPES OF SCISSOR LIFT
MECHANICAL MECHANICAL SCISSOR LIFT
2. HISTORY OF LIFTS
DEVELOPMENT
NECESSITY
TYPES OF LIFTS
3. WORM & WORM WHEEL
INTRODUCTION
FORMS OF THREAD
TERMINOLOGY
4. GEARS
TYPES
RACK AND PINION
TERMINOLOGY
MANUFACTURING
THREAD MANUFACTURING
5. PARTS 6. CONCLUSION & FUTURE WORK
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CHAPTER-1 INTRODUC TION
Simple machines A simple machine uses a single applied force to do work do work against a single load force. Ignoring friction Ignoring friction losses, the work done on the load is equal to the work done by the applied force. The machine can increase increase the amount of the output force, at the cost of a proportional proportional decrease in the distance moved by the load. The ratio of the output to the applied force is called the mechanical the mechanical advantage.
Scissor lift A scissor lift is a type of platform which moves in vertical direction. The mechanism incorporated to achieve this function is the use of linked, folding supports in a crisscross 'X' pattern, known as a pantograph. The upward motion is achieved by the application of pressure to the outside of the lowest set of supports, elongating the crossing pattern, and propelling the work platform vertically upwards. The platform may also have an extending 'bridge' to allow closer access to the work area (because of the inherent limits of only vertical movement). The operation of the scissor action can be obtained by hydraulic, pneumatic or mechanical means (via a lead screw or rack and pinion system). Depending on the power system employed on the lift, it may require no power to enter 'descent' mode, but rather a simple release of hydraulic or pneumatic pressure. This is the main reason that these methods of powering the lifts are preferred, as it allows a fail-safe option of returning the platform to the ground by release of a manual valve.
Types of Scissor lift The scissor lifts can be classified as follows:1. Classification based on the type of energy used (a) Hydraulic lifts (b) Pneumatic lifts (c) Mechanical lifts
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MECHANICAL SCISSOR LIFT
Industrial lifts have traditionally been in use in manufacturing and production settings to raise and lower people, work pieces and
materials. The scissor lift, sometimes
known known as a table table lift, is an industrial industrial lift that has been modified modified for for di d i ff e re nt settings. settings. In basic terms terms, the scissor lift is platform with wheels that acts like a f ork orklif t. In a nonindustrial setting, it is useful for completing tasks which require the speed, mobility and
transporting o f people and material above gro ground. The first scissor lifts were built in the 1970s; 1970s; althou although gh impr ove ment s in materials and safety have been made since then, the underlying basic design is often still used. The concept was ideal for the many retail establishments that were beginning to expand their inventory tory.. Modern scissor lifts maintain a presence in nearly all aspects of manufacturing and production, from construction to assembly assembly to vehicle repair and beyond. LIFT is a mechanical device used to lift or apply great forces. Mechanical lift employ a worm,
worm wheel, rack, pinion for lifting heavy equipment. The most common form is a car lift, floor lift which lifts vehicles so that maintenance can be performed mechanical lifts are usually rated for maximum lifting capacity more powerful jacks use hydraulic power to provide greater lift
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Problem Statement Available lifts present difficulties for the elderly people and women and
are
especially disadvantageous disadvantageous under adverse weather conditions. Presently Presently available lifts further require the operator operator to remain in prolonged prolonged bent or squatting position to operate the lift which is not ergonomic to human body. It will give physical problems in course of time. Moreover, the safety features are also not enough for operator to operate the present lift. The purpose purpose of this project is to overcome these problems. An electric car lift which has a frame ty p e of design by using using ele ctr ici ty from from the car wi ll be developed. developed. Operator Operator frame type of design by using electricity from the car will be developed. Operator only needs to press the button from the controller without working in a bent or squatting position for a long period of time to change change the tire.
Objectives 1. To fabricate mechanical scissor lift which is safe and rel iable to raise and lower the load easily 2. Use of worm, worm wheel, rack and pinion to l ift the loads
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CHAPTER-2 HISTORY OF LIFTS Noted just by several artists, a fabulous telescopic handler; or possibly tele handler and also extendible extendible grasp fork lift li ft is mostly mostly a model popular popular for farming and additionally enterprise. It's always matching in look and additionally feature towa to wards forklift still is normally a great deal more a fabulous crane compared to a an ancient, along with the heightened all-aroun d from the one-time scissor lift which might open up ahead and additionally upwards from used car. Relating to the terminate f or or the scissor lift all the operator may well compliment one of the devices, possibly possibly ocean, end skip out outon on, avenue painting brush . Besides suppleness is normally an alternative good thing about all the telehandler. A lot of varieties a few operator operator the capability to modify software fairly quickly, ultimately causing an overall enhancement enhancement for return return in the exact location. We also have improved suppleness by having a result of the power to space the strain lacking the need to push the machine, merit to these sort of qualities like swivel and additionally team proceed carriages. Still, the luxury of all the telehandler is as well well the country's or the scissor lift stretches or possibly also increases at the same time leading constraint: f or showing a lot, the software antics in the form of lever and additionally can cause the vehicle to start to be very erratic, in the face of counterweights on the backed. Which indicate that all the pushing efficiency fairly quickly cuts down down for the doing business
radius acceler ates. To make sure you tackle this approach, the entire operator gi give vess you a lot record in which helps to the dog verify when the mission is wor work kable, using extra fat, and scissor lift incline and additionally distance off the the ground. As an illustration, it is possible, with this instrument, to distinguish distinguish if you have a used car by having a 5,
000 lb efficiency along with the scissor lift rolled away will probably sole be prepared to risk-f re ree exercise with 400lb in it well fully extended during a poor scissor lift incline, ly,, along with the scissor lift exalted to make sure you be prepared to sustain still will probably 8
even though 10,000 lb. Crashing this approach, a large number of telehandlers start using a laptop computer in which applies devices to make make sure you display the vehicle, all all of which launch a serious all the operator and/or not available farther manipulate effort if f or or example the bounds for the used car really are realized. A lot of makers are likewise
prepared by facade outriggers and that can come to be generally known as wire less cranes, in which open up all the pushing convenience of the gear at the same time writing equipment.
Various Developments in lifting devices 1. Levers 2. Gears
Levers Use of lever gives the operator much mu ch greater greater lift li ftin ing g force than that available to a person who tried to lift lift with with only the the strength of his or her own body. Types of levers are first, second
Gears Gear is a machine element which transmits energy from one shaft to another shaft
Types of gears 1. Spur Gear 2. Helical Gear 3. Herringbone Gear 4. Bevel Gear 5. Worm Gear 6. Rack and Pinion
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Necessity of lifts In the repair and maintenance of automobiles automobiles (car) , it is often necessary to raise an automobile to change a tire or access the underside of the automobile. Accordingly, a variety of car lifts have been be en developed for lifting an automobile from a gro ground surf ace ace. Available car lifts, however, are typically manually operated and therefor erefore
require substantial laborious physical effort on the part of the user. Such lifts present diff diffic icul ulti tie es for for the eld er ly and h an d i ca pp e d
and and ar e e sp e ci al l y disa disadv dva anta ntageou geouss
under adverse weather conditions. Fur Furth ther ermo more re,, a v a i l a b l e lifts lifts are are typ ica lly
larg large, e,
heavy and also difficult to store, transport, carry, or more in to the proper proper position under an automobile. In addition, to the difficulties in assembling and setting up lifts, such
lifts are
generally
not adapted to be be readily disassembled disassembled and stored after
automobile repairs have be been completed. Car lifts must be easy to use for women or whoever had problem with the tire in the middle of nowhere. In light of such inherent disadvantages, commercial automobile repair and service stations are commonly equipped with large and hi-tech car lift, wherein such lifts are raised and lowered via elec trically-powered wered systems. However, due to their size and high costs of purchasing
a nd
maintaining e l ec t r i ca l l y -powered powered car lifts, lif ts, such lifts are not available to the
average car owner.
Engineering
is about making things simpler or improving and
effective. Such electrical powered portable lifts not only remove the arduous task of lifting an automobile via manually operated lifts, but furt furthe herr d e c r e a se the the time time need needed ed to repair the automobile. Such a feature can be especially advantageous advantageous when it i t is necessary to repair repair an automobile on the side of a road way or under other hazardous conditions.
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Types of Lifts Bottle (or) cylinder lift
Bottles screws may be operated by either rotating the screw when the nut is fixed or by
rotating the nut and preventing rotation of the screw. Bottle lift mainly consists of a screw, screw, a nut, thrust bearings, and a body. A stationary platform is attached to the top of the screw. This platform acts as a support for the load and also assists assists it in lifting or lowering of the load. These lifts are are sturdier than the scissor lifts and and can lift heavier loads. In a bottle lift the piston is vertical and directly supports a be aring pad pad that con ta cts the obje ob ject ct being lifted. lif ted. With a single single action action pi st on the lift is somewhat somewhat less than than twice twice the collapsed height of the lift, making it suitable only f or vehicles with a relatively high clearance. Hydraulic Lifts
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Hydraulic lifts are typically used for shop work work, rather than as an emergency lift to be carried with the vehicle. Use of lifts not design for a specific vehicle requires more than the usual care in selecting ground conditions , the lifting point on the vehicle, and to ensure stability when when the lift is extended. A Hydraulic lift uses a fluid, which is in compressible. Oil is used since it is self-lubricating and stable. When the plunger pul ls back back, it draws oil out reservoir through a suction check valve in to the pump chamber. When the of the reservo plunger moves forward, it pushes the oil through a discharge check valve in to the cylinder. The suction valve ball ball is within the chamber and opens with each draw of the plunger. At this point the suction ball with in the chamber is forced to shut and oil
pressure builds in the cylinder.
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CHAPTER-3 WORM & WORM WHEEL
A worm drive is a gear arrangement in which a worm (which is a gear in the f or orm of a
screw) meshes with a worm gear (which is similar in appearance to spur gear). The two eel. The terminology is often elements are also called the worm screw and worm wheel
confused by imprecise use of the term worm gear to refer to the worm, the worm gear gear, or the worm drive as a unit. Like other gear arrangements, arrangements,
a worm drive can reduce
rotational speed or tr ansmit higher torque. The image shows a section of a gear box with a worm gear driven by a worm. A worm is an example of a screw, one of the six simple machin machines Worm gears are used to transmit power at 90° and where high reductions are required. The axes of worm gears shafts cross in space. The shafts of worm gears lie in parallel planes and may be skewed at any angle between zero and a right angle. In worm reads. Due to this, is, worm gears are quiet, vibration free and gear s, one gear has screw threads give a smooth output. 13
Forms of Threads There are three popular types of threads used for worms viz. Square, Trapezoidal , and Acme threads.
Square Threads
orm, used in high applications such as The square thread form is a common screw thread f or lead screws and lift screws. It gets its name from the square cro cross-section of the thread. It is the lowest friction and most efficient thread thread form. The efficiency of square threads is more than that of trapezoidal threads
Trapezoidal Threads
Trapezoidal threads forms are screw thread profiles with with trapezoidal outlines. They are the most common forms used for lead screws screws. They offer high strength and ease of manuf act acture. It is used in lead screw of lathe to compensate wear at periodic levels by
tightening. 14
ACME Threads
Trapezoidal and acme threads are identical in all respects except the
thread
angle. In acme
thread, the thread angle is 29° instead of 30°. The relative advantages and disadvantages of acme threads are same as those of trapezoidal threads. ess thread and it is used where heavy called Buttr es
direction
axial
Ther e
is another type of thread
force acts along the screw axis in one
only.
Terminology of Worm Thread
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1. Pitch : The pitch pitch is defined as the distance, measured parallel to the axis of the screw, from from a point point on one thread thread t o the correspo correspondin nding g p o i n t on the adjacent thread. It is denoted by the letter
“P”.
2. Lead: The lead is defined as the distance, measured measured parallel to the axis of the screw that the nut will advance in one revolution of the screw. It is denoted by the letter
“L”.
For
a single- threaded screw, the lead is same as the pitch, for a doubl double- threaded screw; the lead is twice that of the the pitch, and so on.
3. Nominal diameter : It is the the largest diameter of the screw. It is also also called as major diameter. It is denoted denoted by the letter “d¸”
lled as minor 4. Core diameter : It is the smallest diameter of the screw thread. It is also ca calle
diameter.
5. Helix angle It is defined as the angle made by the helix of the thread with a plane perpendicular to the axis of the screw. Helix angle is related to the lead and the mean diameter of the the screw. Ii is also called as Lead angle.
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CHAPTER-4 GEAR A gear or cogwheel is a rotating machine rotating machine part having cut teeth, or cogs, which mesh with another toothed part to transmit torque. transmit torque. Geared Geared devices can change the speed, torque, and direction of a power source. source. Gears almost always produce a change in torque, creating a mechanical advantage, advantage, through their gear ratio, ratio, and thus may be considered a simple a simple machine. The machine. The teeth on the two meshing gears all have the same shape. Two or more meshing gears, working in a sequence, are called a gear a gear train or a transmission. a transmission. A A gear can mesh with a linear toothed part, called a rack, thereby producing translation producing translation instead of rotation.
Types of Gears 1. Spur Gear Parallel and co-planer shafts connected by gears are called spur gears. The arrangement is called spur gear gearing. eel. Spur gear s Spur gears have straight teeth and are parallel to the axis of the wheel
are the most common type of gears. The advantages of spur gears are their simplicity in design, economy of manufacture manufacture a n d maintenance, a n d absence of end thrust. They impose only radial loads on the bearings bearings. Spur gears are known as slow speed gears. If noise noise is not a serious design problem,
spur gears can be used at almost any speed .
2. Helical Gear Helical gears have their teeth inclined to the axis of the shafts in the form of a helix, ears. These gears are usually thought of as high hence the name helical g gear high speed gears. 17
Helical gears can take higher loads than similarly sized spur gear s. The motion of helical gears is smootherand quieter than the the motionof spur gears. Single helical gears impose both radial loads and thrust loads on their bearings and so
require the use of thrust bearin gs
.
3.
Herringbone Gear Herringbone gears resemble two helical gears that have been placed side by side. They a r e often referred referred to as double helical . In the double helical gears "
"
arrangement, the thrusts are coun ter-balanced. In such double helical gears there
is no thrust loading on the bearings.
4. Bevel Gear Inter Intersec secting ting b u t coplanar s h a f t s connec connected ted b y gears gears are cal led bevel bevel gears. gears. This This arrangement is known known as bevel gearing. gearing. Str aight bevel gears can be used on shafts at any angle, but right angle is the most c ommon. Bevel Gears have conical blanks. The 18
teeth of straight bevel gears are tapered in both thickness and tooth height. (a)Spiral Bevel Gears In these Spiral Bevel gear s, the teeth are oblique. Spiral Bevel gears are quieter and can take up more load as compared to straight straight bevel gears.
(b)Zero Bevel Gears Zero Bevel gears are similar to straight bevel gears, but their teeth are curved rved se. These curved teeth of zero bevel gears are arranged in a manner lengthwise. manner that the
effective spiral angle is zero.
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5. Worm Gear Worm gears are used to transmit power at 90° and where high reductions are required. The axes of worm gears shafts cross in space. The shafts shafts of worm gears lie in parallel planes and may be skewed at any angle between zero and a right angle. In worm is, worm gears are quiet, vibration free and gear s, one gear has screw threads reads. Due to this,
give a smooth output.
Rack Pinion A rack and pinion is a type of linear actuator actuator that comprises a pair of of gears which
convert rotati onal m o t i o n into into lin linea earr mot io n . A circular gear called the pinion "
"
rack ; rotational motion engages teeth on a linear gear bar called the rack motion applied to the "
"
"
"
pinion causes the rack to move relative to the pinion, thereby translating the rotational motion of the pinion into linear motion. railway, the rotation of a pinion mounted on a locomotive For example, in a rack railwa a locomotive or a railcar engages engages a rack a rack between between the rails and forces a a train up up a steep slope. For every pair of conjugate involute profile, there is a basic rac rack k. A generating rack is a rack out outlin line e used to indic indicate ate to toot ot h deta details ils and di dimen men si sions ons for the desig design n of a generating tool, such as a hob or a gear shaper cutter.
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Terminology Used In Gears
Root diameter: It is the diameter of the circle that contains the roots or bottoms of the
tooth spaces.. Pitch point: It is the the intersection between the axis of the line of centers and the line of
action.. Pitch circle : It is the circle through the pitch point having its center at the gear axis Pit ch: It is the distance between similar, equally-space spaced d tooth surfaces in a given direction
along a given curve or line. Helix an gle : It is the angle that a helical gear tooth makes with the gear axis at the pitch
circle, unless specified otherwise. Deden dum: It is the radial or perpendicular distance between the pitch circle and the
bottom of the tooth space. ancce : it is the radial distance between the top of a tooth and the bottom of a mating Cl earan
tooth space. Addendum: It
is the radial or perpendicular distance between the pitch circle and the top
of the too th.
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Gear Manufacturing Gear manufacturing refers to the making of gears. Gears gears. Gears can be manufactured by a variety of processes, including casting, including casting, forging, forging, extrusion, extrusion, powder powder metallurgy, and metallurgy, and blanking. blanking. As As a general rule, however, machining is applied to achieve the final dimensions, shape and surface finish in the gear.
Selection of Gears The gear material should have the following properties:
High tensile High tensile strength to prevent failure against static against static loads
High endurance strength to withstand dynamic withstand dynamic loads
Low coefficient of friction friction
Good manufacturability manufacturability
Gear Manufacturing Process (a) Gear Forming
In gear form cutting, the cutting edge of the cutting tool has a shape identical with the shape
of
the
space
between
the
gear
teeth.
Two
machining
operations, milling operations, milling and broaching and broaching can be employed to form cut gear cut gear teeth (b) Form Milling
In form milling, form milling, the cutter called a form cutter travels axially along the length of the gear tooth at the appropriate depth to produce the gear tooth. After each tooth is cut, the cutter is withdrawn, the gear blank is rotated, and the cutter proceeds to cut another tooth. The process continues until all teeth are cut (c) Broaching
Broaching can also be used to produce gear teeth and is particularly applicable to internal teeth. The process is rapid and produces fine surface finish with high dimensional accuracy. However, because broaches are expensive and a separate broach is required for each size of gear, this method is suitable mainly for high-quality production. 22
(d) Gear Generation
In gear generating, the tooth flanks are obtained as an outline of the subsequent positions of the cutter, which resembles in shape the mating gear in the gear pair. There are two machining processes employed shaping employed shaping and milling. and milling. There are several modifications of these processes for different cutting tool used (e) Gear Hobbing
Gear hobbing Gear hobbing is a machining process in which gear which gear teeth are progressively generated by a series of cuts with a helical cutting tool. All motions in hobbing are rotary, and the hob and gear blank rotate continuously as in two gears meshing until all teeth are cut.
Thread Manufacturing Manufacturing The various methods, which are more or less widely employed for producing screw threads are:
Casting Charac Characte teristics
1. Only a few threads over short length 2. Less accuracy and poor f inish 3. Example-threads at the mouth of glass glass bottles, spun cast iron pipes etc .
Forming (Rolling) Charac Characte teristics
1. Blanks of strong ductile metals like steel are rolled between threaded dies 2. Large threads threads ar a r e hot rolled followed by finishing finishing and smaller threads are straight cold rolled to desired f inis inish
3. Cold rolling attributes more strength and toughness to the threaded threaded parts 4. Widely used for mass mass production production of fasteners like bolts, bolts, screws etc.
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Removal Process (Machining process) 1. Accomplished by various cutting tools in different machine tools like lathes, milling machine, drilling machines (with tapping attachment) etc.
2. Widely used for high accuracy & f inis inish. 3. Employed for wide ranges of threads and volume of production; from piece to mass production.
Finishing (Grinding) Charac Characte teristics
1. Usually done for finishing (accuracy & surface) after performing low machine (or) hot rolling rolling but are often employed employed for for direct threading on rods
2. Precision threads on hard (or) surface hardened components are finished (or) directly produced by grinding only
Non-Conventional Non-Conventional process (EDM, ECM) Charac Characte teristics
1. When conventional methods are not feasible. 2. High precision and micro threads threads are needed. ess. 3. Material is as such difficult to process.
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PARTS
Worm and worm gear
Rack & Pinion
25
Scissor Arms
Mechanical Scissor Lift
26
CONCLUSION & SCOPE In this project a scissor lift which can be operated manually by the use of a worm and worm wheel and rack and pinion mechanism has been studied with required parts and making of each parts with available process. The salient features of the present fabrication are elimination of use of heavy cost equipment through a simple worm & worm wheel and rack and pinion mechanisms. To facilitate convenient operation without heavy operating cost. . Another feature of the unit is provision of worm and worm wheel provides a free movement of lift and it provides a self-locking system. The parts are available and can replace In less time and In easy way
FUTURE WORK The future work deals with the fabrication of the scissor lift with available process which consists of manufacturing of each part precisely and assemble them without any errors in manufacturing
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org/wikilJackscrew [4] http://en.wikipedia.org/ [5] Design and fabrication of motorized automated object tiftingjack; tiftingjack; IOSRJEN.ISSN (e):225O-
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