Basic principle of grinding machine. A.What is grinding machine?
A grinding machine, often shortened to grinder, is a machine tool used for grinding, which is a type of machining of machining using an abrasive wheel as the cutting tool. Each grain of abrasive on the wheel's surface cuts a small chip from the workpiece via shear deformation.
B.Why and when do we need to use it ? Grinding is necessary for the following reasons not only for replace filling:
The material is too hard to be machined economically.
If the surface is adequately supported, grinding can produce flatness tolerances of less than ±0.0001 in. (±0.0025 mm) on a 5 x 5 in. (127 x 127 mm) steel surface.
Machining removes excessive material.
Grinding should be used when size tolerance specifications are beyond the capability of turning.
It is also applied if the requirements of surface finish are too tight for hard turning.
C,How is the grinding process work? The process of grinding can take shape in many forms, but one of the oldest forms of grinding is the grinding ball mill. In this process, a hollow ball is used. Usually, the ball is made of metal, though it can be made of other material as well. Inside of the ball there is some form of grinding media. Grinding media is the material that is used to rise and fall inside of the ball. The fall of the grinding media is what causes the material to be ground. The types of grinding media that is used inside of the grinding ball will depend on the things that are being ground.
The grinding ball continuously rotates over and over causing the grinding media to fall over and over onto the material that is in the grinding ball to be made into a fine powder. This process may take some time. Depending on the material to be ground and how fine it needs to be ground down. However, this process is automated and makes it possible for the process to take far fewer people to accomplish the work. In many grinding balls the material is able to put into one end and then come out of the other end when it is sufficiently ground down. This makes the process even more automated and less labor intensive
vertical spindle
l horizontal spindle
D.Type of grinding machine stress more about surface grinding.
1.Horizontal-spindle (peripheral) surface grinders The periphery (flat edge) of the wheel is in contact with the workpiece, producing the flat surface. Peripheral grinding is used in high-precision work on simple flat surfaces; tapers or angled surfaces; slots; flat surfaces next to shoulders; recessed surfaces; and profiles.
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2.Vertical-spindle (wheel-face) grinders The face of a wheel (cup, cylinder, disc, or segmental wheel) is used on the flat surface. Wheel-face grinding is often used for fast material removal, but some machines can accomplish high-precision work. The workpiece is held on a reciprocating table, which can
be varied according to the task, or a rotary-table machine, with continuous or indexed rotation. Indexing allows loading or unloading one station while grinding operations are being performed on another.
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3.Disc grinders and double-disc grinders Disc grinding is similar to surface grinding, but with a l arger contact area between disc and workpiece. Disc grinders are available in both vertical and horizontal spindle types. Double disc grinders work both sides of a workpiece simultaneously. Disc grinders are capable of achieving especially fine tolerances
E.Machine parts and functions
Machine parts 1)base
functions Serves as a foundation member for all the other parts which rest upon it. It carries the column at its one end.
2)column
main supporting frame mounted vertically on the bag
3)knee
The rigid gray iron casting that slides up and down on the vertical way of the column face.
4)saddle
Slides on guide ways set exactly at 90 to column face and to provide guide ways for the table.
5)table
The table rest on ways on the saddle and travels longitudinally. The top of the table is accurately finished and T-slots are provided for clamping the work and other fixtures on it.
6)over hanging arm
Machine parts 1)base
Serve as a bearing support may be provided nearest to the cutter.
functions Serves as a foundation member for all the other parts which rest upon it. It carries the column at its one end.
2)column
main supporting frame mounted vertically on the bag
3)knee
The rigid gray iron casting that slides up and down on the vertical way of the column face.
4)saddle
Slides on guide ways set exactly at 90 to column face and to provide guide ways for the table.
5)table
The table rest on ways on the saddle and travels longitudinally. The top of the table is accurately finished and T-slots are provided for clamping the work and other fixtures on it.
6)over hanging arm
Serve as a bearing support may be provided nearest to the cutter.
Wheel A.Grinding wheel materials.
Aluminum Oxide (A) Silicon Carbide (C) Diamond (D, MD, SD) Cubic Boron Nitride (B) B.Available wheel shapes. 1.Straight wheel
To the right is an image of a straight wheel. These are by far the most common style of wheel and can be found on bench or pedestal grinders. They are used on the periphery only and therefore produce a slightly concave surface ( hollow ground ) on the part. This can be used to advantage on many tools such as chisels. Straight Wheels are the kind of generally used for cylindrical, centreless, and surface grinding operations. Wheels of this form vary greatly in size, the diameter and width of face naturally depending upon the class of work for which is used and the size and power of the grinding machine. 2.Cylinder or wheel ring Cylinder wheels provide a long, wide surface with no center mounting support (hollow). They can be very large, up to 12" in width. They are used only in vertical or horizontal spindle grinders. Cylinder or wheel ring is used for producing flat surfaces, the grinding being done with the end face of the wheel. 3.Tapered wheel A straight wheel that tapers outward towards the center of the wheel. This arrangement is stronger than straight wheels and can accept higher lateral loads. Tapered face straight wheel is primarily used for grinding thread, gear teeth etc. 4.Straight cup Straight cup wheels are an alternative to cup wheels in tool and cutter grinders, where having an additional radial grinding surface is beneficial. 5.Dish cup A very shallow cup-style grinding wheel. The thinness allows grinding in slots and crevices. It is used primarily in cutter grinding and jig grinding. 6.Saucer wheel
A special grinding profile that is used to grind mil ling cutters and twist drills. It is most common in non-machining areas, as sawfilers use saucer wheels in the maintenance of saw blades.
7.Diamond wheel
Diamond wheels are grinding wheels with industrial diamonds bonded to the periphery.
They are used for grinding extremely hard materials such as carbide cutting tips, gemstones or concrete. The saw pictured to the right is a slitting saw and is designed for slicing hard materials, typically gemstones. 8.Diamond mandrels Diamond mandrels are very similar to their counterpart, a diamond wheel. They are tiny
diamond rasps for use in a jig grinder doing profiling work in hard material. 9.Cut off wheels Cut off wheels, also known as parting wheels, are self-sharpening wheels that are thin in
width and often have radial fibres reinforcing them. They are often used in the construction industry for cuttingreinforcement bars (rebar), protruding bolts or anything that needs quick removal or trimming. Most handymen would recognise an angle grinder and the discs they us Criteria of the wheel 1.Grain size, from 8 (coarsest) 600 (finest), determines the physical size of the abrasive grains in the wheel. A larger grain will cut freely, allowing fast cutting but poor surface finish. Ultra-fine grain sizes are for precision finish work. 2.Wheel grade, from A (soft) to Z (hard), determines how tightly the bond holds the abrasive. Grade affects almost all considerations of grinding, such as wheel speed, coolant flow, maximum and minimum feed rates, and grinding depth. 3.Grain spacing,
or structure, from 1 (densest) to 16 (least dense). Density is the ratio of bond and abrasive to air space. A less-dense wheel will cut freely, and has a large effect on surface finish. It is also able to take a deeper or wider cut with less coolant, as the chip clearance on the wheel is greater. 4.Wheel bond, how the wheel holds the abrasives, affects finish, coolant, and minimum/maximum wheel speed.
Vitrified (V)
Resinoid (R)
Silicate (S)
Shellac (E)
Rubber (R)
Oxychloride (O)
C.Wheel balancing
1. Remove out the wheel adaptor and the balancing weight 2. Before install the new grinding wheel, check the grinding wheel by knocking the grinding wheel and differential the sound of the grinding wheel 3. After mounting the new grinding wheel fix the unit onto the spindle and rough true grinding wheel so that it has a true roundness. 4. Remove out the grinding wheel from machine and insert the balancing arbour into the griding wheel flange. 5. Place the grinding wheel balancing stand and level the unit by checking the level gauge. 6. Place the grinding wheel with arbour onto the balancing stand. 7. Turn the grinding wheel run freely until it comes to a rest, the bottom point may be the heavier side(W). 8. Then tighten one of the balancing weight at opposite side of the heavier point(W). 9. And then tighten two pieces balancing weights(AA) in a symmetry. 10. Adjust an each opening angle(A) must be according to the amount of inbalance. 11. Adjust the position of the balancing weight repeatedly until the grinding wheel is in the good balance when turned in any positions on the balancing stand.
Accessories A.Clamping techniques used in the grinding processes Method for grinding a machine component having at one longitudinal axial end a journal and at its other longitudinal axial end an interior recess having a rotationally symmetrical surface, comprising rotating the machine component about a longitudinal axis thereof, grinding exterior surfaces thereof with a first grinding wheel and grinding said surface of said interior recess with a second grinding wheel, a workpiece headstock, a tailstock, and at least one steady being provided for clamping said machine component during grinding, wherein said grinding method comprises the following sequential steps: a) effecting a first clamped condition in which a chuck of said workpiece headstock surrounds said journal of said machine component with releasable clamping jaws and at the same time a centering tip of the workpiece headstock engages an end face of said journal, while a tip of a sleeve of the tailstock engages in said interior recess of said machine component; b) in the first clamped condition, with the first grinding wheel grinding a seat for the steady on an exterior circumference of said machine component and grinding predetermined areas on surfaces of the exterior circumference of said machine component with the exception of said journal; c) effecting a second clamped condition in which said machine component is supported at said steady seat by said steady and said tailstock is moved far enough away from said machine component in an axial direction of the machine component that said second grinding wheel can be inserted into said interior recess of said machine component upon being moved from an idle position;
d) in the second clamped condition, moving the second grinding wheel from the idle position, inserting the second grinding wheel is said interior recess and grinding therewith said rotationally symmetrical surface of said interior recess; e) returning said second grinding wheel to its idle position, rendering said steady is inactive, and reinstating the f irst clamped condition; f) effecting a third clamped condition n which said clamping jaws of said chuck of said workpiece headstock are released from said journal and drawn axially into said chuck such that said machine component is then clamped only between the centering tip of said workpiece headstock and said tailstock sleeve; g) in the third clamped condition, with the first grinding wheel grinding a circumference of said journal.
B,Measuring instruments suitable for grinding product
1. Dial caliper 2. Vernier caliper
ASSIGNMENT 2 GRINDING MACHINE
NAME : AKALIL JAZLI BIN JASRI ID : FB10025(F08)
