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Grinding and super finishing

1. UNIT 2. Grinding & Super Finishing

2. Surface Finish
•Surface finish isa measurement of the overall texture of a surface.
•Surface finishing is the final step of manufacturing that enhances the
appearance, durability, and functionality of a product's outer layer.
•After various machining operations like turning, boring, milling, shaping
& drilling produces fairly accurate surface sizes they do not produce high
degree of surface finish, So this step is necessary for better appearance
of surface.

3. Significance of Grinding in Manufacturing
•To achieve high dimensional accuracy.
•Provide high precision and tight tolerances.
•Enhance surface quality and finish.
•Reducing roughness &improve aesthetic appearance.
•Improve the wear resistance, fatigue life and friction properties by
refining the surface quality.
•Sharpen the cutting tools and create precise edges for enhance
performance.

4. Features of Grinding Process
1. Mechanical Features:
i. Abrasion: Grinding uses abrasive particles to remove material.
ii. Cutting: Grinding can be considered as cutting process with
multiple cutting edges.
2. Thermal Features:
i. Heat Generation: Grinding generates heat due to friction and deformation.
Ii. Temperature Rise: Temperature rise can occur in the workpiece,
grinding wheel, and surrounding environment.

5. Features of Grinding Process
3. Geometric Features:
i. Surface Finish: Grinding can produce high surface finish and precision.
ii. Dimensional Accuracy: Grinding can achieve high dimensional accuracy.
iii. Form Generation: Grinding can generate complex forms and shapes.
4. Operational Features:
i. Speed and Feed: Grinding speed and feed rates can be adjusted.
ii. Wheel Wear: Grinding wheel wear can affect process performance.
iii. Material Removal Rate: Grinding can achieve high material removal rates.
iv. Noise and Vibration: Grinding can generate noise and vibration

6. Advantages Of Grinding Process
1. Achieve high dimensional accuracy.
2. Extreme smooth and desirable surface finish
3. High material removal rate
4. Flexible and versatile
5. Low equipment and operating cost
6. Improved surface integrity
7. Can grind hard and brittle materials.
8. improve aesthetic appearance.

7. Application Of Grinding Wheel
1.To remove very small amount of metal from the workpiece
for close tolerance.
2.To obtain better surface finish .
3.Intermediate cut &finishing.
4.To sharpen the cutting tool.

8. Grinding Wheels Composition
Making of grinding wheel :
•The wheels are generally made with composite material. This consists of
coarse-particle aggregate pressed and bonded together by a cementing
matrix (called thebondin grinding wheel terminology) to form a solid,
circular shape.
•Grinding wheels are characterized by the following characteristics :
•(i) Kind of abrasive material
•(ii) Grain size
•(iii) Bond
(iv) Hardness or grade
(v) Structure
(vi) Shape and sizes

9. Grinding Wheels Composition
Abrasives Grains :-
•Grinding wheels are made up of abrasive particles.
•Abrasive is hard material which can be used to cut
or wear away other materials.
•Types of abrasive grains,
1. Natural grain : (Sand, Diamond, Quartz)
2. Artificial grain : (Synthetic diamond, Tin oxide,
Aluminum oxide, Silicon Carbide)
3. Super abrasives grain : Cubic boron nitride (CBN).
•In industry artificial abrasives are used commonly.

10. Grain Size or Grit
•The Grain & Grit number indicate the size of abrasive use for making the
grinding wheel, These size of particles are called grain or grit
•Grain size affects the quantity of material removed & surface quality obtained.
•The grain size selected is based on product material, type of grinding process,
required surface finish and material to be removed from the job surface.
•The green size is designated by the number from 10 to 600 in which 10 is for
coarser and 600 for being finer.
•Grain size number indicates number of meshes per inch.
•A 100-mesh screen means there are 100 little square openings across one inch
of screen.

11. Grain Size or Grit
•The various abrasive grain sizes commonly used are classified as follow.

12. Bond
•A bond is type of binding material that holds the abrasive grains together,
allowing the mixture to be kept in a desired shape or form of wheel.
The bonding material should have following properties :-
1.Bonding material should withstand the grinding temperature.
2.Bonding material should withstand the spindle speed without
disintegration.
3.Bonding should be residwhich easy to cut the work.
4.The bond makes strong adhesion between wheel and abrasive particle.

13. Types Of Bonding Material
•There are various types of bonding materials are given below

14. Types Of Bonding Material
1. Vitrified Bond:-
•Vitrified bonds are composed of clay, feldspar, and
quartz, which are mixed and heated to form a
glass-like bond.
•This bond is strong, rigid, and resistant to oils and water.
•Vitrified bonds are suitable for general-purpose grinding, cylindrical
grinding, and surface grinding.
•They offer high strength, good dimensional stability, and relatively
low cost.

15. Types Of Bonding Material
2. ResinoidBond :-
•Resinoidbonds are made from synthetic resin,
often with added fillers and modifiers.
•They are flexible, impact-resistant, and suitable
for high-speed grinding.
•Resinoidbonds are commonly used for grinding steels, cast irons, and
non-ferrous metals.
•They offer flexibility, resistance to shock and vibration, and can be
used at high speeds.

16. Types Of Bonding Material
3. Rubber Bond :-
•Rubber bonds are composed of natural or
synthetic rubber.
•They are flexible, elastic, and suitable for
grinding delicate surfaces.
•Rubber bonds are often used for grinding precision parts, bearing
surfaces, and other delicate components.
•They offer flexibility, absorb vibrations, and produce smooth finishes.

17. Types Of Bonding Material
4. Metallic Bond :-
•Metallic bonds are made from metal powders
or wires, often with added binders.
•They are strong, durable, and resistant to
high temperatures.
•Metallic bonds are commonly used for grinding hard materials, such as
ceramics and glass.
•They offer high strength, good thermal conductivity, and can be used at
high speeds.

18. Types Of Bonding Material
5. Shellac Bond :-
•Shellac bonds are composed of natural resin,
often with added fillers and modifiers.
•They are flexible, impact-resistant, and suitable
for grinding delicate surfaces.
•Shellac bonds are often used for grinding precision parts, bearing
surfaces, and other delicate components.
•They offer flexibility, absorb vibrations, and produce smooth finishes.

19. Hardness or Grade
•The grade means degree of hardness with which the bond holds the cutting
points or abrasive grains in a place. It does not refer the hardness of abrasive
grain.
•Hard wheels are recommended for soft material and soft wheel are
recommended for hard material.
•The grade is described in alphabetical order; A being the softest and Z being
the hardest.
•The words ‘Hard’ & ‘Soft’ refer the holding power or strength of the bond.

20. Structure
•The abrasive grains are held in the bonding material and the relative distance
between the grains defines the structure of wheel.
•It can also defined as the number of cutting points per unit area of the wheel face.
•Soft and ductile materials are ground by open structure and hard and brittle
materials are grounded by dense structure.
•The structure of wheel is denoted by number from 1 to 15 or more in order of
dense to open respectively.

21. Dressing Of Grinding Wheels

22. Dressing Of Grinding Wheels

23. Dressing Of Grinding Wheels
•Dressing of a grinding wheel is the process of re-shaping the abrasive
particles on the surface of the wheel to restore its cutting ability.
•This is done by using a “dressing tool” which is typically a separate
tool or a device built into the grinding machine.
•Dressing isthe act of removing dulled or worn abrasive grains from
the surface of a wheel, allowing fresh, sharp grains to take their
place.

24. Why Dressing Of Grinding Wheel Is Important ?
•Improves Wheel-Cutting Ability, Speed and Efficiency
•Extends Wheel Lifespan and Reduces Replacement Costs.
•Improves WorkpieceSurface Finish, Dimensional Accuracy & Integrity.
•Extends WorkpieceLifespan and Reduces Rework or Scrap Costs.

25. How To Dress A Grinding Wheel
Step 1 :-Put on safety wear like goggles or a welding mask
Step 2 :-Check the wheel and dressing tool for any crack or defects
Step 3 :-Turn on the wheel and let it reach its maximum RPM
Step 4 :-Place the dressing tool on the rest and slowly slide it
across the wheel
Step 5 :-Apply light to medium pressure and move the tool back
and forth to smooth out rough spots
Step 6 :-Continue until the wheel starts to tug the tool away

26. Truing Of Grinding Wheels

27. Truing Of Grinding Wheels

28. Truing Of Grinding Wheels
•Trueing is the process of changing the shape of the wheel to correct its
profile and restore its geometric accuracy.
•The main purpose of truing is ensuring that the periphery of the wheel
is concentric with the spindle.
•Truing is necessary for grinding operations to achieve accurate and
consistent results. When a grinding wheel is not properly trued, it can
lead to several problems like Inaccuracy in dimensions, poor surface
finish, vibration and too much grinding force required.

29. Why Truing Of Grinding Wheel Is Important ?
•To restore the original shape and geometry of the grinding wheel.
•To ensuring the concentricity with its central spindle or bore.
•To eliminate the deformation such as runout or uneven
surfaces causes by wear.
•To ensure the grinding will maintain precise dimension.

30. How To True A Grinding Wheel
Step 1 :-A diamond-pointed tool is slowly and precisely fed across
the wheel as it rotates.
Step 2 :-The tool removes any irregularities or damages that may
have occurred during grinding operations.
Step 3 :-The wheel's periphery is made concentric with its axis.
Step 4 :-The wheel's side is made true.