Manufacturing Technology- ii Unit 4 PPT By Ravisankar.G

1. Unit 4 - ABRASIVE PROCESSES AND
BROACHING
G.Ravisankar, Asst Prof , Mechanical, Sri
Eshwar college of Engineering , Coimbatore .

2. UNIT IV - ABRASIVE PROCESSES AND BROACHING
2
Abrasive processes: grinding wheel – specifications
and selection, types of grinding process–cylindrical
grinding, surface grinding, centreless grinding and
internal grinding- Typical applications –concepts of
surface integrity, broaching machines: broach
construction – push, pull, surface and continuous
broaching machines
1. Hajra Choudhury, "Elements of Workshop Technology", Vol.II., Media
Promoters
2. Rao. P.N “Manufacturing Technology - Metal Cutting and Machine Tools",
Tata McGraw-Hill, New Delhi, 2003.

3. Abrasive processes - Outline
• Abrasives
• Grinding
▫ Grinding Wheels
▫ Grinding Process
• Coated Abrasives
▫ Belt Grinding
• Honing
• Lapping
• Other Finishing Operations
• Deburring Processes

4. Abrasive Machining
Abrasive machining is a material removal process that
involves the use of abrasive cutting tools.
There are three principle types of abrasive cutting
tools according to the degree to which abrasive
grains are constrained,
•Bonded abrasive tools
• Coated abrasive tools
• Free abrasives

5. Abrasive Machining

6. Abrasive Machining
Why a smooth surface?
• Reduction in Friction
▫ Heat - Bearings
• Reduction in Wear
▫ Bushings/Bearings
• Appearance
▫ Car Body, Furniture
• Clearance
▫ Disk Head
• Sharpness
▫ Cutting Tools

7. Abrasive Machining
How do we get a smooth surface?
• Remove Material
▫ Abrasive Machining
• Flatten
▫ Burnishing – polish the metal by rubbing.
• Fill in Voids
▫ Add material
▫ Paint
▫ Finish
▫ Wax

8. Abrasives
• Small, hard nonmetallic particles with sharp edges
and irregular shapes
• Can remove small amounts of material, producing
tiny chips
• Abrasive processes can produce fine surface
finishes and accurate dimensional tolerances

9. Types of Abrasives
Conventional Abrasives
a. Aluminum oxide (Al2O3)
b. Silicon carbide (SiC)
Super abrasives
c. Cubic Boron Nitride (cBN)
d. Diamond
Natural abrasives (sand stone, emery, diamond)
Abrasives are harder than conventional tool materials

10. Abrasive Factors
- Grain size
- Grain shape
- Hardness
- Friability (tendency to fracture)

11. Abrasive Material

12. Abrasive Hardness and Thermal Conductivity

13. Grinding
• Grinding is the most common form of abrasive
machining.
• It is a material cutting process which engages an
abrasive tool whose cutting elements are grains of
abrasive material known as grit.
• These 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.

14. Grinding
• Cutting action of abrasive grains

15. Grinding

16. Example of a Grinding Machine

17. Major advantages of grinding
A grinding wheel requires two types of specification
• dimensional accuracy
• good surface finish
• good form and locational accuracy applicable to
both hardened and unhardened material

18. Major applications of grinding
Applications
• surface finishing
• slitting and parting
• descaling, deburring
• stock removal (abrasive milling) finishing of flat as
well as cylindrical surface
• grinding of tools and cutters and resharpening of
the same.

19. Types of Grinding
- Surface Grinding
- Cylindrical Grinding
- Internal Grinding
- Centerless Grinding
- Others
- Tool and cutter grinders
- Tool-post grinding
- Swing-frame grinders
- Bench grinders
- Creep-Feed Grinding

20. Floor stand, Bench grinding

21. Portable grinding

22. Abrasive belt, Swing frame

23. Surface Grinding

24. Horizontal spindle reciprocating table

25. Surface Grinding
• Surface grinding is an abrasive machining process in
which the grinding wheel removes material from the
plain flat surfaces of the work piece.

26. Cylindrical Grinding

27. Cylindrical Grinding

28. PRECISION GRINDING
1. Cylindrical grinding

29. Types of cylindrical grinding
• Plunge grinding (form tool method)

30. Plain center type cylindrical grinding

31. Center type universal grinding

32. Cylindrical Grinding
• Three types of feed motion are possible according
to the direction of feed motion,

33. Internal Grinding

34. Internal Grinding
1.Chucking type internal
grinding
2.Planetary type

35. Centerless grinders

37. Centerless Grinding
• Centerless grinding is a process for continuously
grinding cylindrical surfaces in which the work
piece is supported not by centers or chucks but by
a rest blade.
• The work piece is ground between two wheels.
• The larger grinding wheel does grinding, while the
smaller regulating wheel, which is tilted at an
angle i, regulates the velocity Vf of the axial
movement of the work piece.

38. Centerless Grinding

39. Centerless Grinding

40. Center less grinding

41. Creep-Feed Grinding
• Grinding has traditionally been associated with small
rates of material removal and finishing operations.
• However, grinding can also be used for large-scale
metal removal operations similar to milling, shaping,
and planing.
• In creep-feed grinding, the depth of cut d is as much as
6mm, and the workpiece speed is low.
• The wheels are mostly softer grade resin bonded with
open structure to keep temperatures low.
• Creep-feed grinding can be economical for specific
applications, such as grinding cavities, grooves, etc.

42. Creep-Feed Grinding

43. Special purpose grinding machine
1.Form Tool, Gear Teeth Grinding 2. Cam grinding

44. 3. Tool and cutter grinder

45. Bonded Abrasives/ Grinding Wheels
Bonded Abrasives
• Most grinding wheels are made of abrasive grains
held together by a bonding material
Types of bonding material:
• Vitrified (glass)
• Resinoid (thermosetting resin)
• Rubber
• Metal (the wheel itself is metal; the grains are
bonded to its surface

46. Grinding Wheel Components

47. Grinding Wheel - Structure

48. Grinding Wheel - Shapes

49. Grinding Process
Grinding
- Grains have irregular shapes and random spacing
- Average rake angle is very negative (about -60° or
lower)
- Radial positions of grains vary
- Cutting speed is very high (ca. 600 ft/min)

50. Grinding Process

51. Grinding Process
Grain force
 ((v/V)√(d/D))(material strength)
Temperature rise
 D1/4d3/4(V/v)1/2
Effects caused by grinding temperature increase:
- Sparks
- Tempering
- Burning
- Heat Checking

52. Grinding Wheel – Standard marking system
• Grade

54. Grinding Wheel - Loading

55. Grinding Wheel - Wear
Types:
• Attritious Grain Wear
Grains develop a wear flat
• Grain Fracture
Necessary to produce sharp grain edges
• Bond Fracture
Allows dull grains to be dislodged from the
wheel

56. Grinding Wheel - Parameters
• The way the abrasive grains, bonding material, and
the air gaps are structured, determines the
parameters of the grinding wheel,
which are
• Abrasive material,
• Grain size,
• Bonding material,
• Wheel grade,
• Wheel structure.

57. Truing and Dressing

58. Cutting Fluids
- Remove heat
- Remove chips, grain fragments and dislodged
grains
- Are usually water-based emulsions
- Are added by flood application

59. Grinding Ratio
G = Volume of material removed
Volume of wheel wear
Vary greatly (2-200 or higher) depending on the
type of wheel, grinding fluid, and process
parameters
Higher forces decrease the grinding ratio

60. Grinding
Design Considerations:
- Design parts so that they can be held securely
- Avoid interrupted surfaces if high dimensional
accuracy is required because they can cause
vibrations
- Ensure cylindrical parts are balanced and thick
enough to minimize deflections
- Short pieces may be difficult to grind accurately in
centerless grinding because of limited support by the
blade
- Parts requiring high accuracy form grinding should be
kept simple to prevent frequent wheel dressing
- Avoid small deep or blind holes or include a relief

61. Coated Abrasives
Coated Abrasives
Abrasive grains are deposited on flexible backing;
they are more pointed than those in grinding
wheels
Common examples: sandpaper, emery

62. Coated Abrasives

63. Coated Abrasives
Belt Grinding
Uses coated abrasives in the form of a belt; cutting
speeds are about 2500-6000 ft/min
Microreplication
Abrasives with a pyramid shape are placed in a
predetermined regular pattern on the belt

64. Belt Grinding

65. BROACHING
65

66. Broaching
• Broaching is the process of removing metal with a
tool which has “teeth” arranged in a row. Each
tooth is successively higher than the previous
tooth and removes more material. In broaching,
one stroke or cycle of the machine produces a
finished part.
• Broaching is used to produce both internal and
external features. Production rates are high and
tolerances of +/- .0005” are possible.

67. Broaching
Broaching machine is a process of machining
surface with a special multipoint cutting tool
38-67

68. Tool Feed Direction
Gullet
Workpiece
Depth of
cut per tooth
Tool
Broaching

69. Specification of broaching machine
• Max length of the stoke
• Max force developed by the slide in tonnes
• Types of drives
• Power rating of electrical motor in HP
• Speed and feed
• Weight of the machine
• Floor space required

70. Advantages & Disadvantages
▫ Advantages
 Rough to finish in one pass
 Production rates are high
 Cutting time is quick
 Rapid load and unload of parts
 External and internal features
 Any form that can be produced on a broaching tool can
be produced
 Production tolerances are excellent
 Surface finishes are equal to milling
 Operator skill is low

71. Advantages & Disadvantages
▫ Disadvantages
 Tooling cost can be high
 In some cases--not suited for low production rates
 Parts to be broached must be strong enough to
withstand the forces of the process
 Surface to be broached must be accessible

72. TYPES OF BROACHING MACHINE
According to the nature and direction of primary cutting motion
▫ Horizontal broaching machine
▫ Vertical broaching machine
▫ Continuous broaching machine
According to the purpose
▫ Internal broaching machine
▫ External surface broaching machine
According to method operation
▫ Pull broaching machine
▫ Push broaching machine
According to the construction of the broach tool
▫ Solid broaching machine
▫ Inserted tooth broaching machine
▫ Progressive cut broaching machine
▫ Built-up broaching machine

73. • According to the function
▫ Keyway broaching machine
▫ Burnishing broaching machine
▫ Spline broaching machine
▫ Round hole broaching machine
▫ Surface broaching machine
• According to the number of main slides or stations
▫ Single broaching machine
▫ Double broaching machine
▫ Multiple slides broaching machine
• According to the motion of the broach tool relative to the
work
▫ Straight line motion broaching machine
▫ Stationary broach tool broaching machine

74. Horizontal broaching machine

75. Vertical broaching machine

76. Continuous broaching machine

77. Continuous broaching machine

78. Nomenclature of Broaching tool

79. Types of broaching tool
According to the method of operation
▫ Push Broach
▫ Pull Broach
According to the kind of operation
▫ Internal Broach
▫ External Broach
According to their construction
▫ Solid Broach
▫ Built up of replaceable section
▫ Inserted tooth Broach
▫ Overlapping teeth Broach
▫ Progressive cut Broach

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