Milling and gear cutting machines

Milling operations-types of milling cutter. Gear cutting – forming and generation principle and construction of gear milling, hobbing and gear shaping processes –finishing of gears.

1. MANUFACTURING PROCESS-II By Arul R Assistant Professor Mechanical Engineering Department [email protected] 08-10-2021 1

2. MILLING AND GEAR GENERATING MACHINES Milling — specifications — types - cutter nomenclature — types of cutters — milling processes — indexing — gear forming in milling — gear generation - gear shaping and gear hobbing — specifications - cutters — cutting spur and helical gears - bevel gear generators — gear finishing methods

3. LECTURE-1 Milling Machines 08-10-2021 3

4. MILLING MACHINE

5. Milling

6. Milling machine Milling: is a metal cutting operation in which the excess material from the work piece is removed by rotating multipoint cutting tool called milling cutter. A milling machine is a machine tool that removes metal as the work is fed against a rotating multipoint cutter. The milling cutter rotates at high speed and it removes metal at a very fast rate with the help of multiple cutting edges. One or more number of cutters can be mounted simultaneously on the milling machine. This is the reason that a milling machine finds wide application in production work. Used for machining flat surfaces, contoured surfaces, external and internal threads.

7. Milling machine As the workpiece moves against the cutting edges of milling cutter, metal is removed in form chips Machined surface is formed in one or more passes of the work. The work to be machined is held in a vice, a rotary table, a three jaw chuck, an index head, in a special fixture or bolted to machine table. In many applications, due to its higher production rate and accuracy, milling machine has even replaced shapers and slotters.

8. Milling machine applications

9. M ILLING METHODS Two basic methods of milling Up-milling or conventional milling Down-milling or climb milling 1.Up-milling or conventional milling M e tal is r e m o v ed by cutter r o tating against the direction of travel of the workpiece. Needs stronger holding of the job. Chip thi c k n ess i s m in i m u m a t the start of cut and maximum at the end of the cut. Disadvantage- tendency to lift work from the fixtures and poor surface finish.

10. 1.C ONVENTIONAL MILLING

11. M ILLING METHODS 2.down-milling or climb milling M e tal is re m o v ed by cu t ter r o tat i ng in the s a m e direction of travel of the workpiece. teeth cut downward instead of upwards. Chip thi c k n ess i s m ax i m u m a t the st a rt of cut and minimum at the end of cut. Less friction involved Better surface finish. Less power consumption.

12. 2.C LIMB MILLING

13. PRINCIPLE OF MILLING

14. T YPES OF MILLING MACHINE The milling machine may be classified in several forms, but the choice of any particular machine is determined primarily by the size of the workpiece. According to general design, the distinctive types of milling machines are: Column and knee type milling machines Planer milling machine Fixed-bed type milling machine Special types of milling machines

15. P RINCIPLE PARTS Base Colu m n Knee Saddle Table Spindle

16. C OLUMN AND KNEE TYPE It is the most commonly used milling machine used for general shop work. The table is mounted on the knee which in turn is mounted on the vertical slides of the main column. The knee is vertically adjustable on the column so that the table can be moved up and down to accommodate work of various heights.

17. C LASSIFIACTION OF COLUMN & KNEE TYPE MILLING MACHINE Hand milling m/c. Horizontal milling m/c. Universal milling m/c. Vertical milling m/c.

18. ( a ) Horizontal Milling machine The horizontal milling machine has a spindle that is parallel to the shop floor and an overarm that extends over the workpiece. The overarm supports the arbor, which holds the milling cutter. On the horizontal mill, the arbor is the component that rotates the milling cutter.

19. A CTUAL HORIZONTAL MILLING MACHINE

20. A RBORS Fig : Mounting a milling cutter on an arbor for use on a horizontal milling machine.

21. ( B ) V ERTICAL MILLING MACHINE Spindle is vertical or perpendicular to the work table. It has all the movements of the table for proper setting and feeding the work. Spindle head may be swiveled at an angle, permitting the milling cutter mounted on the spindle to work on angular surfaces. In some machines, spindle can also be adjusted up or down relative to the work. Adopted for machining grooves, slots and flat surfaces.

22. VERTICAL MILLING MA C HINE MAJOR PARTS : BASE COLUMN SPINDLE SPINDLE HEAD KNEE SADDLE WORKTABLE

23. DIFFERENCES BETWEEN HORIZONTAL & VERTICAL MILLING MACHINES SL. NO. HORIZONTAL MILLING MACHINE VERTICAL MILLING MACHINE 01 Spindle is horizontal & parallel to the worktable. Spindle is vertical & perpendicular to the worktable. 02 Cutter cannot be moved up & down. Cutter can be moved up & down. 03 Cutter is mounted on the arbor. Cutter is directly mounted on the spindle. 04 Spindle cannot be tilted. Spindle can be tilted for angular cutting. 05 Operations such as plain milling, gear cutting, form milling, straddle milling, gang milling etc., can be performed. Operations such as slot milling, T-slot milling, angular milling, flat milling etc., can be performed and also drilling, boring and reaming can be carried out.

24. ( C ) U NIVERSAL MILLING MACHINE Difference from plain horizontal machine is addition of table swivel housing Permits table to be swiveled 45º in either direction in a horizontal plane Used for milling of helical grooves in twist drills, milling cutters, and gears

25. 2. Fixed-bed type milling machine Comparatively large, heavy and rigid and differ from column and knee type milling machines. Table is directly mounted on fixed bed. No provision is provided for cross or vertical adjustment of the table. The cutter mounted on the spindle head may be moved vertically on the column and the spindle may be adjusted horizontally to provide cross adjustment. Three types 1. Simplex 2. duplex 3. triplex

26. F IXED BED MILLING MACHINE

27. 3. P LANER MILLING MACHINE Looks like double column planer machine. Milling heads mounted in various planes, vertical heads on the cross-rail and horizontal heads at the sides (on column) This arrangement enables it to machine a workpiece on several sides simultaneously Used for producing long straight surfaces on large and heavy machine parts.

28. 5. S PECIAL -T YPE M ACHINES Designed for individual milling operations Used for only one particular type of job Completely automatic Employed when hundreds or thousands of similar pieces are to be machined Tracer mills (Profiling milling machines): Also called duplicators Designed to reproduce an irregular part geometry that can be created on an template In two dimensions- tracer In three dimensions- duplicator

29. S PECIAL -T YPE M ACHINES CNC milling machines: - Cutter path controlled by numerical data - Suited to profile, pocket, surface contouring.

30. MILLING OPERATIONS Plain or slab milling Face milling End milling Side milling Slot milling Angular milling Form milling Straddle milling

31. MILLING OPERATIONS Slitting or saw milling Gear cutting Key way milling String milling Profile milling Thread milling Helical milling Cam milling

32. PLAIN/SURFACE/ SLAB MILLING Plain Milling: Process to get the flat surface on the work piece in which the cutter axis and work piece axis are parallel. The primary motion is the rotation of the cutter. The feed is imparted to the work piece. Cutter: Plain milling cutter. Mach i n e : Horizo n tal Milling m/c.

33. PLAIN/SURFACE/ SLAB MILLING Work piece Plain mill cutter

34. FACE MILLING Face Milling: o u t for Operation carried producing a fl a t s u rface, which is perpendicular to the axis of rotating cutter . Cutter: Face milling cutter. Machine : Vertical Milling Machine

35. F ACE MILLING M ANUFACTURING T ECHNOLOGY

36. END MILLING FIG. END MILLING End Milling: Operation performed for producing flat surfaces, key slots, grooves or finishing the edges of the work piece. Cutter: End milling cutter. Machine: Vertical Milling Machine

37. SIDE MILLING SIDE MILLING : Operation performed for producing flat surfaces, slots, grooves or finishing the edges of the work piece. Cutter: End milling cutter. Machine: Horizontal Milling Machine

38. SLOT MILLING FIG. T-SLOT MILLING Slot Milling: Operation of p roducing slots l ike T -s l ots , plain slots etc., Cutter: End milling cutter, T-slot cutter, side milling cutter Machine: Vertical Milling Machine

39. ANGULAR MILLING FIG. ANGULAR MILLING Angular Milling: Oper a ti o n o f p r o d u c ing all types of angular cuts like V- notches and g r o o v e s, serrations and angu l ar surfaces. Cutter: Double angle cutter. Machine: Horizontal Milling Machine

40. FORM MILLING Form Milling: Operation of producing al l types o f angula r cuts and like V-notches gro o ve s , serration s a n d angular surfaces . Cutter: Double angle cutter . Machine: Horizontal Milling Machine

41. FORM MILLING

42. STRADDLE MILLING FIG. STRADDLE MILLING Straddle Milling: Operation of machining two s u r f a c es on a work parallel si m ul t ane o us l y piece. Cutter : 2 or more side & face milling cutters Machine : Horizontal Milling Machine

43. GANG MILLING FIG. GANG MILLING Gang Milling: Process to get different profiles on the work piece simultaneously with two or more cutters at one stretch. Cutter: Different cutters as required. Machine: Horizontal Milling Machine

44. Profile milling Outside periphery of flat part is cut . Conventional end mill is used to cut the outside or inside periphery of a flat part.

45. Another form of end milling used to mill shallow pockets into flat parts Pocket Milling

46. S URFACE C ONTOURING Ball - nose cutter is fed back and forth across the work along a curvilinear path at close intervals to create a three dimensional surface.

47. This process uses a pinion shaped cutter carrying clearance on the tooth face and sides and a hole at its center for mounting it on a stub arbor or spindle of the machine. The cutter is mounted by keeping its axis in vertical position. It is also made reciprocating along the vertical axis up and down with adjustable and predecide amplitude . GEAR SHAPING METHOD

48. GEAR SHAPING MACHINE

49. GEAR PLANING In this method, gear cutting is done by a rack shaped cutter called rack type cutter. The process involves rotation (low rpm) of the gear blank as the rack type cutter reciprocates along a vertical line. Cutting is done only in the downward stroke, the upward stroke is only a return movement.

50. GEAR PLANING

51. GEAR HOBBING In this process, the gear blank is rolled with a rotating cutter called hob. Gear hobbing is done by using a multipoint cutting tool called gear hob. In gear hobbing operation, the hob is rotated at a suitable rpm and simultaneously fed to the gear blank. The gear blank is also kept as revolving. Rpm of both, gear blank and gear hob are so synchronized that for each revolution of gear bob the gear blank rotates by a distance equal to one pitch distance of the gear to be cut. Motion of both gear blank and hob are maintained continuously and steady.

52. GEAR HOBBING

53. FINISHING OF GEARS Sur f ace o f g ea r t e e th p r odu c e d by a n y o f the g ene r a t ing p r oce s s i s not accu r at e and o f g ood quali t y (smooth). Dimen si on a l inaccuracies and r ough sur f ace g ene r a t e d so become the source of lot of noise, excessive wear, play and backlash between the pair of gears in mesh .

54. GEARS FINISHING METHODS GEAR SHAVING ROLL FINISHING OF GEAR TOOTH GEAR BURNISHING * Gear Grinding Lapping of a Gear GEAR HONNING

55. GEAR SHAVING Gear shaving is a process of finishing of gear tooth by running it at very high rpm in mesh with a gear shaving tool. A gear shaving tool is of a type of rack or pinion having hardened teeth provided with serrations. These serrations serve as cutting edges which

56. GEAR SHAVING

57. ROLL FINISHING OF GEAR TOOTH This process involves use of two hardened rolling dies containing very accurate tooth profile of the gear to be finished. The gear to be finished is Yet in between the two dies.

58. ROLL FINISHING OF GEAR TOOTH

59. GEAR BURNISHING The gear to be finished is mounted on a vertical reciprocating shaft and it is kept in mesh with three hardened burnishing compatible gears. The burnishing gears are fed into the cut gear and revalued few revaluations in both the directions. Plastic deformation of irregularities in cold state takes place to give smooth surface of the gear .

60. Gear Grinding operation ab r asi v e grindi n g In this whe e l of a pa r ticu l ar shape and geometry are used for finishing of gear teeth. Gear to be finished is mounted and reciprocated under the grinding wheel. Each o f the g e ar t e e th is subjected to way. gr i ndi n g ope r a tions this

61. Gear Grinding

62. Lapping of a Gear The process of lapping is used to improve surface finish of already made teeth. In this process the gear to be lapped is run under load in mesh with cast iron toothed laps. Abrasive paste is introduced between the teeth. It is mixed with oil and made to flow through the teeth. One of the mating members (either gear or lapping tool) is reciprocated axially along with the revaluations .

63. GEAR HONNING It i s used f o r super fini s hing o f the g ene r a t e d g ea r t e e t h . H o ning machines are generally used for this ope r a t io n . Th e h o nes a r e rubbed against the profile generated on the g ea r t o o t h . Gea r lapp i n g and g ear honi n g a r e the lo s t a gear fin i shing g ene r a ti o n ope r a t ions of process.