abrasive technologies

1. ABRASIVE MACHINING PROCESS

2. INTRODUCTION
Rz: Maximum height of the
roughness profile
Ra: Arithmetical mean deviation
of the roughness profile
 Usually brought into play after machining, casting, forging, sheet metal forming, etc.
 It can be used on all type of materials.
 A variety of abrasive machining processes and machinery is available.
 Abrasive machining is necessary and economical when:
 Hard materials
 Brittle materials
 Excellent surface finish and dimensional tolerances are required.
 Roughness 2D Parameters
Rq: Root mean square deviation
of the roughness profile
Profilometer

3. GRINDING
Introduction
 It is an abrasive technology in which abrasive particles are contained in bonded grinding wheel.
 The feed (f) and depth of cut (d) in grinding are small, while the cutting speed (V) is high.
 Dimensional accuracy: 0.3 – 0.5 µm
 Surface finish (Ra) ~ 0.1 – 1.6 µm
VIDEO

4. GRINDING
 Material cutting process which engages an abrasive tool whose cutting elements are grains
of abrasive material known as grit.
 Grits are characterized by sharp cutting points, high hot hardness, chemical stability and
wear resistance.
 The grits are held together by a suitable bonding material to give shape of an abrasive tool.
Grinding Wheel & Workpiece interaction
grit

5. Introduction
GRINDING
 A grinding wheel consists of:
 Conventional abrasive wheel materials:
• Aluminium oxide (Al2O3)
• Silicon carbide wheels (SiC)
 Superabrasive wheels:
• Diamond
• CBN (Cubic Boron Nitride)
Conventional abrasive wheels Superabrasive wheels
Hard abrasive grains called grits perform the cutting or material removal Hardness
Bonding material holds particles in place and gives the profile to the wheel Toughness

6. 1 14192 250 X 25 X 25 51-A-36-L-5-V-23 40m/s
GEOMETRY DIMENSIONS COMPOSITION Max SPEED
PRODUCT
NUMBER
GRINDING
Grinding wheel specification
The heavy point of the
grinding wheel is marked
with an arrow. Depending of
the wheel manufacturer, it
needs to be mounted with
the arrow pointing
downwards or upwards. VIDEO

7. GRINDING
Grinding wheel specification

8. CBN (4000-5000) very hard materials
Diamond (7000-8000) carbide & very hard non ferrous materials
ABRASIVE GRAIN SIZE:
GRADE (abrasive grain-bonding joining strength):
Soft wheel hard materials machining (to have fresh abrasive) or poor Ra = roughing Hard
wheel soft materials machining or excellent Ra = finishing
STRUCTURE (porosity):
BOND TYPE:
Vitrified: most common, brittle bond
Resinoid: more flexible bond
Rubber: very flexible bond
GRINDING
VIDEO
Al2O3 (2000-3000 ) high tensile strength materials, ductile materials
SiC (2100-3000) low tensile strength, brittle and non metallic materials
Coarse Soft & ductile materials or poor Ra = roughing
Fine Hard & brittle materials or excellent Ra = finishing
Open Soft & ductile materials
High removal rate or poor Ra = roughing
Dense Long wheel life & precise wheel forms/profiles or excellent Ra = finishing
Grinding wheel specification

9.  Truing is the process of making a grinding wheel round and concentric with the grinding wheel
spindle axis. Truing is also the process of forming a specific shape on the face of the wheel.
 Dressing is the process of conditioning the surface of a trued wheel to expose the grain for
efficient grinding action.
GRINDING
After dressing
 Truing and dressing can often be performed at the same time, even using the same tool.
Truing and dressing a grinding wheel
After truing

10. Grinding-Truing a grinding wheel
Grinding-dressing a grinding wheel
Video
Video

11. Types of Grinding Process

12. GRINDING
 It is used to remove material from flat surfaces.
 Spindle position can be horizontal or vertical.
 Dimensional tolerance ~ IT5 – IT6
 Surface finish (Ra) ~ 0.15 – 0.6 µm
Types of Grinding Process
1.Flat or surface grinding

13. Flat or surface grinding
Video

14. ALTERNATIVE
WORKTABLE
ALTERNATIVE
WORKTABLE
ROTATIVE
WORKTABLE
ROTATIVE
WORKTABLE
 Long and narrow surfaces.
 Worse efficiency than the frontal grinding.
 Better finishing than the frontal grinding.
 High material start-up rate.
 Worse finishing than the
tangential grinding.
 Tools: rings, cups, segments
GRINDING
TANGENTIAL GRINDING WHEEL FRONTAL GRINDING WHEEL
VIDEO VIDEOVIDEO
Types of Grinding Process
1.Flat or surface grinding

15. surface grinding Tangential grinding wheel
surface grinding Frontal grinding wheel
Video
Video
1.Flat or surface grinding

16. Engine Cutting blade
GRINDING
APPLICATIONS
Gear
TANGENTIAL
FRONTAL FRONTAL
TANGENTIAL TANGENTIAL
VIDEO
Guide Props Other
Types of Grinding Process
1.Flat or surface grinding

17. GRINDING
2.Creep feed grinding
 It uses large depth of cuts (typically ap on the order of 1 - 6 mm) and low feed rates (F).
 The wheel is often continuously dressed.
 It is essential to use a high pressure coolant system and soft wheels with open structure to keep
temperature low.
 Advantages: High material removal rates and productivity (the wheel is continuously cutting).
Conventional grinding contrasted to creep feed grinding
Types of Grinding Process

18. GRINDING
APPLICATIONS
Gas turbine bladeGear Other parts
Types of Grinding Process
2.Creep feed grinding

19. 3.Cylindrical grinding
GRINDING
 It is used to remove external or internal cylindrical surfaces.
 It is also known as Universal grinding.
 The workpiece is usually held in a rotating chuck in the headstock or between
centers.
 The wheel rotates at very high rotational speed (N).
• Dimensional tolerance ~ IT6 – IT8
• Surface finish (Ra) ~ 0,8 – 1,6 µm
VIDEO
Types of Grinding Process

20. GRINDING
Types of Grinding Process
3.Cylindrical grinding
External grinding
Internal grinding operations
VIDEO
(a) Traverse grinding (b) Plunge grinding (c) Profile grinding

21. Cylindrical grinding Application
Internal grinding
3.Cylindrical grinding
Video
Video

22.  The part rotation and the distance x between
centers is varied and synchronized to grind the
particular workpiece shape.
Cylindrical grinding
SPECIAL OPERATIONS
GRINDING A NON-CYLINDRICAL PART
GRINDING
VIDEO
Types of Grinding Process

23. Cylindrical grinding Special operations
Crankshaft grinding
Special operations Thread grinding
SPECIAL OPERATIONS
Video
Video

24. Cylindrical grinding
APPLICATIONS
GRINDING
Transmission shaft
Internal axis gear Aerospace rotor
Axle Spindle housing
VIDEO
Types of Grinding Process

25. 4.Centerless grinding
EXTERNAL GRINDING
OPERATIONS
GRINDING
• Dimensional tolerance ~ IT4 – IT6
Surface finish (Ra) ~ 0.4 – 0.8 µm
(a) Through-feed grinding
 It is used for high length to diameter ratio parts.
Workpiece is NOT supported by centers or chucks,
but by a blade or between rollers.
 Easy to be automatizated.
(a) Through-feed grinding (b) Plunge grinding
Types of Grinding Process

26. Centerless grinding External grinding
Centerless grinding External grinding Through-
feed grinding
4.Centerless grinding
Video
Video

27. Centerless grinding
INTERNAL GRINDING OPERATIONS
(c) Internal centerless grinding
GRINDING
Types of Grinding Process

28. GRINDING
APPLICATIONS
Bars / tubes
Gearbox shaft
Camshaft tube
Piston
Types of Grinding Process

29.  The work is held (usually manually) against the flat surface of the wheel to accomplish the
grinding operation.
 It can be a bench grinder or pedestal grinder.
Surface finish (Ra) ~ 0.2 – 1.6 µm
GRINDING
VIDEO
Types of Grinding Process
BENCH GRINDING

30. BLASTING, WIRE BRUSHING, MASS
FINISHING, HONING, POLISHING AND
BUFFING, LAPPING, SUPERFINISHING

31. This is the finishing method by spraying blasting abrasives from a nozzle with
the force of compressed air to workpieces.
 It is used for:
 Cleaning
 Deburring
 Descaling
 Finishing
 Surface finish (Ra) ~ 1.5 µm
1. BLASTING
VIDEOVIDEO
Video

32. 2. WIRE BRUSHING
It produces a fine and controlled surface texture.
Wire brushing is typically used for:
removal of rust or corrosion from metal objects.
rough-polishing castings, hot-rolled steel,…
 Brushes can be made of nylon, steel or brass filaments, and may contain abrasives.
 Surface finish (Ra) ~ 0.1 – 1.5 µm
VIDEOVideo

33. 3. MASS FINISHING
It is used for:
 Deburring
 Smoothing
 Descaling
 Luster and mirror finishing.
There are several types of barrel motion:
HIGH
 Centrifugal
barrel
 Centrifugal disc
 Vibratory bowl
 Rotary tumbling
 Surface finish
(Ra)
~ 0.05 – 1.6 µm
LOW
Centrifugal barrel
Centrifugal disc
VIDEO VIDEO
Vibratory bowl Barrel / Rotary tumbling
VIDEO
VIDEOVIDEO
Mass finishing is a surface improving mass-production system. A mixture of parts, abrasive
media (vitrified, alumina, plastic, organic or metallic) and compounds (liquid or powder) are
placed into a container or barrel, and rotated at a predetermined speed.

34. MASS FINISHING
Video

35. 4. HONING
 Honing is used to improve the surface finish and roundness of bored or ground holes.
 It creates a characteristic cross-hatched surface that retains lubrication.
 As it is a slow rotation operation, no heat affected zone (HAZ) appears.
 Typical application: bores of internal combustion engines.
(Al2O3 or SiC)
OscillationVa
Slow rotation
Vu
VIDEO
Video

36. 5. POLISHING
Abrasive particles are glued to the outside periphery of the polishing wheel and it rotates at high
speeds.
 Polishing is used to remove scratches and burrs.
 Polishing operations are often accomplished manually.
 The polishing wheel is made of fabrics, leather or felt.
 Surface finish (Ra) ~ 0.02 – 0.4 μm
BEFOREAFTER
VIDE

37. It is very similar to polishing, in which abrasive particles are not glued to the wheel but are loose.
Buffing is a finer operation than polishing.
 Ideal for enhancing and brightening existing finishes, taking out stains in metals
and bringing out a new lustre in work surfaces.
 Polishing operations are often accomplished manually.
 The buffing wheel is made of linen, cotton, flannel, or other soft cloth materials.
 Surface finish (Ra) ~ 0.01 – 0.2 μm
6. BUFFING
Video

38. 7. LAPPING
lapping on cylindrical surfaces
 It is a low speed, low ablading process.
Lapping uses fluid suspension of very small abrasive particles between
workpiece and lap. Lap usually made of cast iron, copper, leather, or cloth.
 Typical application: optical lenses, metallic bearing surfaces, gages.
 Dimensional tolerance ~ IT4 – IT5
 Surface finish (Ra) ~ 0.025 – 0.1 μm
VIDE
Video

39. 8. SUPERFINISHING
 `It is similar to honing (also called “microhoning”):
 Shorter strokes (<5 mm)
 Higher frequencies (>400 cycles/min) Lower pressures (10-40 psi)
 Smaller grit size
 Copious amount of low viscosity lubricant-coolant is used and it establishes a continuous
film between the stone and the workpiece and separates them.
 Stroke paths controlled so that a single grit never traverses the same path twice.
 Dimensional tolerance ~ IT3 – IT4
 Surface finish (Ra) ~ 0.01 – 0.04 μm
cylindrical microhoning VIDEOVIDEO
VIDEO
Video

40. SUPERFINISHING
Video