MANUFACTURING PROCESS-II UNIT-4 ABRASIVE PROCESS

MANUFACTURING PROCESS-II UNIT-4 ABRASIVE PROCESS

1. UNIT - IV ABRASIVE PROCESS AND BROACHING 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

2. ABRASIVE PROCESS Grinding is mainly used for the following purposes: To remove small amount of metal from the work pieces and finish them to close tolerances To obtain a better surface finish Sharpening of cutting tools

3. GRINDING WHEEL Grinding wheels are made up of small abrasive particles held together by bonding materials. Grinding wheel abrasives Natural abrasives Artificial abrasives

4. Natural Abrasives These are produced by uncontrolled forces of nature. These are obtained from mines. Sandstone or solid quartz Emery (50 to 60% crystalline Al 2 o 3 + iron oxide) Corundum (75 to 90% crystalline Al 2 o 3 + Iron oxide) diamond

5. Artificial Abrasives These are manufactured under controlled conditions in closed electric furnace in order to avoid the introduction of impurities and to achieve the necessary temperature for the chemical reaction to take place. Aluminium oxide Silicon carbide Artificial diamond Boron carbide Cubic boron nitride

6. TYPES OF BOND Bond is an adhesive substance which holds the abrasive grains together to form the grinding wheel. Bonds are classified into two types. Organic Non - organic

7. Organic Resinoid bond Rubber bond Shellac bond Oxy chloride bond

8. Non - organic Vitrified bond Silicate bonds

9. SPECIFICATION OF GRINDING WHEEL Grit or Grain size Grade Structure of wheels

10. Grit or Grain size

11. Grade

12. Structure of wheels

13. DESIGNATION OF GRINDING WHEEL The following elements are represented in a definite order type of abrasives Grain size or grit number Grade of the wheel Structure Type of bond Manufacture’s code

14. SELECTION OF GRINDING WHEEL The selection of a proper grinding wheel very important for getting the best results in grinding work. The grinding wheel selection will depend the following factors Constant factors Variable factors

15. Constant factors Physical properties of material to be ground Amount and rate of stock to be removed Areas of contact Type of grinding machine

16. Variable factors Work speed Wheel speed Condition of the grinding machine Personal factors

17. RECONDITIONING OF GRINDING WHEEL Dressing Star dressing tool Round abrasive Diamond dressing tool Truing

18. Star dressing tool

19. Round abrasive

20. Diamond dressing tool

21. SHAPES OF GRINDING WHEEL

22. MOUNTING WHEELS AND POINTS

23. TYPE OF GRINDING MACHINES According to the type of operation According to the quality of surface finish According to the type of surface generated

24. Further classification Rough grinders Floor stand grinders Bench grinders Portable grinders Abrasive belt grinders Swing frame grinders Precision grinders Cylindrical grinders Internal grinders Surface grinders Tool and cutter grinders Special grinders

25. Rough grinders Rough grinders are mainly used for removing large amount of metal from the work piece. Therefore the surface finish and the accuracy in dimension are not high.

26. Floor stand grinders

27. Bench grinders

28. Portable grinders

29. Abrasive belt grinders

30. Swing frame grinders

31. Precision grinders Precision grinders are used to manufacture parts of accurate dimensions and good surface finish. The work piece and the grinding wheel are rigidly mounted but they are adjustable according to the requirement of the machining methods

32. Cylindrical grinders There are four movements in a cylindrical centre type grinding. Rotation of cylindrical work piece about its axis Rotation of the grinding wheel about its axis Longitudinal feed movement of the work past the wheel face Movement of the wheel into the work perpendicular to the axis of the work piece to give depth of cut

33. Type of grinding operations are carried out Transverse grinding Plunge grinding

34. Type of cylindrical grinding Plain centre type cylindrical grinding machine Centre type universal grinder

35. Surface grinders Surface grinding machines are used to produce and finish flat and plane surfaces. By using special fixtures and form dressing devices, angular and formed surfaces can also be ground. Horizontal spindle reciprocating table surface grinder Horizontal spindle rotary table surface grinder Vertical spindle reciprocating table surface grinder Vertical spindle rotary table surface grinder

36. Horizontal spindle reciprocating table surface grinder

37. Horizontal spindle rotary table surface grinder

38. Vertical spindle reciprocating table surface grinder

39. Vertical spindle rotary table surface grinder

40. CENTRELESS GRINDERS Centreless grinding is performed on work pieces which do not have centres, such as pistons, valves, rings, shafts etc. centreless grinding can be done on both external and internal cylindrical surfaces.

41. METHODS OF EXTERNAL CENTRELESS GRINDING There are three different methods Through feed In feed End feed

42. Internal grinders There are three types of internal grinders Chucking type Planetary type Centreless type

43. Chucking type

44. Planetary type

45. Centreless type

46. TYPICAL APPLICATIONS OF GRINDING MACHINES Form grinders Thread grinding Cam grinding Tool and cutter grinding

47. Form grinders

48. Thread grinding

49. Cam grinding

50. Tool and cutter grinders

51. CUTTING FLUIDS IN GRINDING It cools the workpiece It acts as a lubricant and reduces friction between chips, workpiece and grinding wheel. It removes chips from the contact area

52. CONCEPTS OF SURFACE INTEGRITY Surface integrity is the surface condition of a workpiece after completing by a particular manufacturing process. In grinding process, the surface integrity of ground specimen is analysed. Classification of surface integrity Traditional process Non traditional process Finishing treatment

53. BROACHING Broaching is a process of machining a surface with a special multipoint cutting tool called broach which has successively higher cutting edges in a fixed path. It is a faster and cheaper method of machining but the depth of removed material is limited to 6mm or less. Broaching the inside surface is called “internal or hole broaching” and the outside surface is known as “surface broaching”.

54. SPECIFICATION OF A BROACHING MACHINE Maximum length of stroke in mm. Maximum force developed by the slide in tonnes. Power rating of electric motor in H.P Speed and feed ranges Weight of the machine Floor space required

55. ADVANTAGES OF BROACHING Roughing , semi-finishing and finishing cuts are completed in one pass of the broach. Broaching can be used for either external or internal surface finishing processes. Semi skilled worker can perform a broaching operation Broaching is mostly adopted for mass production.

56. LIMITATIONS Initial cost of the broach tool is high when compared to other tools Broaching is not suitable for the removal of large amount of stock. Almost all the work pieces will need the fixture for rigid support.

57. TYPES OF BROACHING MACHINE Horizontal broaching machine Vertical broaching machine Continuous broaching machine

58. Horizontal broaching machine Horizontal type internal broaching machine Horizontal type surface broaching machine

59. Horizontal type internal broaching machine

60. Horizontal type surface broaching machine

61. VERTICAL BROACHING MACHINES Pull up type Pull down type Push down type

62. Pull up type

63. Pull down type

64. Push down type

65. CONTINUOUS BROACHING MACHINE Horizontal type Vertical type Rotary type

66. Horizontal type

67. Rotary type

68. BROACH NOMENCLATURE

69. TYPE OF BROACHING TOOLS Push broach Pull broach Progressive broach

70. Push broach

71. Pull broach

72. Progressive broach

73. BROACHING OPERATIONS Broaching splines Broaching a keyway

74. Broaching splines

75. Broaching a keyway

76. Thank you