1. Machining Manufacturing Processes © 2012 Su-Jin Kim GNU Manufacturing Processes Cutting (Machining) 절삭가공 Su-Jin Kim School of Mechanical Engineering Gyeongsang National University

2. Machining Manufacturing Processes © 2012 Su-Jin Kim GNU Cutting 1.Cutting mechanics 2.Tool wear 3.Tool material 4.Turning, Turning center 5.Milling, Machining center

3. Machining Manufacturing Processes © 2012 Su-Jin Kim GNU Cutting mechanics ( 절삭역학 ) Chip formation  Shear break off Cutting force = Specific energy x Area Chatter (vibration) Cutting temperature Tool wear Tool life equation

4. Machining Manufacturing Processes © 2012 Su-Jin Kim GNU Chip Formation ( 칩생성 ) Chips are produced by the shearing taking place along a shear plane.

5. Machining Manufacturing Processes © 2012 Su-Jin Kim GNU Cutting Force ( 전단이론 ) According to maximum-shear-stress criterion, yielding occurs when the max shear stress within an element is equal to or exceeds a critical value (shear yield stress). Tool (Assume no friction) Fc σ1σ1 Stock σσ1σ1 τ τ Ф Mohr’s circle Shear angle Shear plane

6. Machining Manufacturing Processes © 2012 Su-Jin Kim GNU Cutting Force (Shear force theory) Shear Force = Shear Stress * Shear Area Shear Area = Width x Depth / sin (Shear Angle) t0t0 φ t 0 /sin( φ ) Tool w FsFs

7. Machining Manufacturing Processes © 2012 Su-Jin Kim GNU Cutting Force (Theory) Resultant force = Shear force / cos (shear angle + friction angle – rake angle) Tool α β-αβ-α ф Workpiece Fs R β Chip

8. Machining Manufacturing Processes © 2012 Su-Jin Kim GNU Cutting Force (Theory) Cutting force = Resultant force x cos (friction angle – rake angle) Shear angle = pi/4 + rake angle/2 – friction angle/2 Tool α β-αβ-α ф Workpiece Fc R Chip

9. Machining Manufacturing Processes © 2012 Su-Jin Kim GNU Cutting Force Rake angle ↑  shear angle ↑, cutting force ↓  chip thickness ↓, cooler chip ↓ Rake angle ↑  tool section ↓  strength at cutting edge ↓, heat conductivity ↓ Relief angle ↑  friction ↓  tool life ↑, surface quality ↑ Relief angle ↑  strength at cutting edge ↓ Nose radius ↓  heat ↓, surface quality ↑ Force ↑< yield stress of stock ↑, cut depth ↑, cut width ↑ Rake angle,α Relief angle, r + Shear angle, φ Nose radius

10. Machining Manufacturing Processes © 2012 Su-Jin Kim GNU Cutting Force Approximation ( 절삭력 ) Cutting force ≈ Specific cutting energy( 비절삭에너지 ) x Cutting area F c ≈ u t A c Cutting power = force x velocity P = F c V Tool Stock AcAc FcFc MaterialSpecific cutting energy (GPa) Tensile strength (MPa) Aluminum alloys0.4-1.1480 Copper alloys1.4-3.3500 Cast irons1.6-5.5200 Steels2.7-9.3840

11. Machining Manufacturing Processes © 2012 Su-Jin Kim GNU Ex ) Cutting Force Turning steel, depth of cut d = 0.1 mm, feedrate f = 0.01 mm/rev, Specific cutting energy of steel u = 2.7~9.3 GPa. Cutting force? Cutting speed v = 10 m/s. Cutting power? F = u A = u d f = 2.7~9.3 (10^9 N/m^2) x 0.001 x 10^-6 m^2 = 2.7~9.3 N P = F v = 2.7 ~ 9.3 N x 10 m/s = 27 ~ 93 W

12. Machining Manufacturing Processes © 2012 Su-Jin Kim GNU Chip morphology ( 칩생성 ) Type of chips produced influences surface finish and machining operation. 1.Continuous chips 2.Built-up-edge chips 3.Serrated chips 4.Discontinuous chips Steel: http://www.youtube.com/watch?v=4bOzJiYAZD4http://www.youtube.com/watch?v=4bOzJiYAZD4 Cast Iron: http://www.youtube.com/watch?v=RoooeTEEMxY&feature=relatedhttp://www.youtube.com/watch?v=RoooeTEEMxY&feature=related Stainless: http://www.youtube.com/watch?v=DzAjpHFy4fwhttp://www.youtube.com/watch?v=DzAjpHFy4fw

13. Machining Manufacturing Processes © 2012 Su-Jin Kim GNU Chip breaker Chip breaker  shorter chip GrooveChip breaker

14. Machining Manufacturing Processes © 2012 Su-Jin Kim GNU Chatter (Self-excited vibration) Chatter vibrating with high frequency noise is caused by interaction of chip-removal process with flexibility of the tool. It could be avoided by increasing dynamic stiffness and damping, by decreasing depth of cut and proper selection of spindle speed. Chatter Safe http://www.youtube.com/watch?v=uv3yUCl27wM Spindle (rmp) Depth of cut (mm)

15. Machining Manufacturing Processes © 2012 Su-Jin Kim GNU Temperature ( 절삭열 ) Cutting power P=FV  Heat  Increase the temperature of chip, work piece, and tool - Temperature increase = specific heat x mass : dT = c m - Specific heat (kJ/kgK): iron 0.45, aluminium 0.91, copper 0.39 As temperature increases, it will affect the properties of the cutting tool, dimensional accuracy. - Thermal extension: dL = a dT L - Thermal extension coefficient of iron 10 x 10^-6

16. Machining Manufacturing Processes © 2012 Su-Jin Kim GNU Ex) Temperature of chip Material removal rate? m/t = ρ A v = (kg/s) If we assume 100% of cutting power used to heat chip, Temperature of chip? P = Q/t = c dT m/t If workpiece temperature increased 10 ℃, thermal expansion of workpiece?

17. Machining Manufacturing Processes © 2012 Su-Jin Kim GNU Tool wear ( 공구마모 ) Mechanical wear 1.Abrasive wear - hardness 2.Adhesive wear - junction 3.Fatigue wear - crack (toughness) Thermo Chemical wear 1.Diffusion wear ( 확산 ) 2.Solution wear ( 용해 )

18. Machining Manufacturing Processes © 2012 Su-Jin Kim GNU Tool wear The wear behaviour of cutting tools are flank wear(measure width of wear land), crater wear(at high speed, diffusion wear is the major reason, measure depth), nose wear, and chipping of the cutting edge. crater wear flank wear nose wear broken edge

19. Machining Manufacturing Processes © 2012 Su-Jin Kim GNU Material (ISO P K M) Steel cutting  All and upper face wear and deformation Stainless cutting  Built-up-edge & notch wear Cast iron cutting  All face wear and deformation

20. Machining Manufacturing Processes © 2012 Su-Jin Kim GNU Tool life (F.W. Taylor, 공구수명 ) Tool-wear relationship for cutting various steels is Tool-life is also effected by depth and feed rate. V : cutting speed / T : time (min) / C : constant. n : exponent depends on cutting conditions HSS 0.14-0.16, Carbides 0.21-0.25, TiC insert 0.30, PCD 0.33, TiN insert 0.35, Ceramic coated insert 0.40 Cutting speed V Tool life T Log C -n d : depth of cut, f : feed rate Carbide Ceramic HSS

21. Machining Manufacturing Processes © 2012 Su-Jin Kim GNU Given that n=0.5 and VT n =C, if the V reduced 50%, calculate the increase of tool life. Solution VT 0.5 =C(1) 0.5VT 2 0.5 =C(2) (2)/(1) 0.5(T 2/ T) 0.5 =1 T 2 =4T Increase tool life 4 times. Ex Increasing tool life by reducing the cutting speed

22. Machining Manufacturing Processes © 2012 Su-Jin Kim GNU Surface Finish ( 표면조도 ) Feed marks In turning, peak-to-valley roughness is r r <R f r : feed rate (mm/rev) R : tool nose radius (mm) Tool Stock R frfr rtrt

23. Machining Manufacturing Processes © 2012 Su-Jin Kim GNU Cutting Tool Materials ( 공구 재질 ) HSS ( 하이스 ) Carbide ( 초경 ) Cermet CBN Diamond

24. Machining Manufacturing Processes © 2012 Su-Jin Kim GNU Cutting-Tool Materials A cutting tool has the following characteristics: 1.Hardness ( 경도 ) at high temperature ~ Speed 2.Toughness ( 인성 ) ~ Feed & depth 3.Wear resistance ( 내마모성 ) 4.Chemical stability ( 화학적 안정성 )

25. Machining Manufacturing Processes © 2012 Su-Jin Kim GNU HSS ( 하이스 ) HSS (High-speed steels) HSS cuts faster than carbon tool steel, hence the name high speed steel, but slower than carbide tools. It is often used in power saw blades and drill bits. TiN-Coated HSS PVD (physical vapor deposition), TiN coating reduces tool wear.

26. Machining Manufacturing Processes © 2012 Su-Jin Kim GNU Carbides ( 초경 ) Carbides Better wear resistance, stiffness, hot hardness Tungsten carbide: WC + Co(for toughness)  powder metallurgy (sintered), suitable for non-ferrous, grey cast iron Titanium carbide: TiC + Co : TiC is suitable for steel and cast iron Coated Carbide Carbide + TiC, TiN, Al 2 O 3 coated by CVD (chemical vapor deposition) Chemically stable  greatly reduce crater wear

27. Machining Manufacturing Processes © 2012 Su-Jin Kim GNU Cermets Ceramics Aluminum oxide(Al 2 O 3 ), Silicon-nitride(SiN), cold pressed and hot sintered Hot hardness ↑, toughness ↓ (chipping), thermal shock Cermets Ceramic(Al 2 O 3 ) + metal binder(TiC) Hot hardness ↑, toughness ↓, thermal expansion ↑ Insert: less thermal stress, eliminate grinding by user, less setting time http://www.youtube.com/watch?v=Om9gzgNPf80

28. Machining Manufacturing Processes © 2012 Su-Jin Kim GNU Diamond, CBN Diamond (Poly crystal diamond) Hardest material, Not good for steel CBN (polycrystalline cubic boron nitride) 2nd hardest material, brittle, expensive http://www.youtube.com/watch?v=vAvfrrlMZg4 http://www.youtube.com/watch?v=mKxX50OMBd4&p=9B6D9EAE75875D9D

29. Machining Manufacturing Processes © 2012 Su-Jin Kim GNU Tool materials Tool materials, feeds, and cutting speeds Characteristics of cutting-tool materials gives a range of cutting speeds and feeds for different applications. Coated HSS / HSS Feed (Toughness) Speed (Hardness) Coated carbide Carbide Cermet Cera mic PCD CBN

30. Machining Manufacturing Processes © 2012 Su-Jin Kim GNU Workpiece materials ( 소재 재질 ) Workpiece materials and cutting speeds when Carbide tool or coated carbide tools is used for turning MaterialCutting speed (m/min) Aluminum alloys200-1000 Copper alloys50-700 Cast iron, gray60-900 Steels50-500 Titanium alloys10-100

31. Machining Manufacturing Processes © 2012 Su-Jin Kim GNU Cutting Tool Makers ( 공구 제작사 ) www.taegutec.co.kr www.yg1.co.kr

32. Machining Manufacturing Processes © 2012 Su-Jin Kim GNU Cutting Fluids ( 절삭유 ) Also called lubricants and coolants, cutting fluids. Used extensively in machining operations to: 1.Cool the cutting zone 2.Reduce friction and wear 3.Reduce forces and energy consumption 4.Wash away chips 5.Protect surfaces from any environmental attack

33. Machining Manufacturing Processes © 2012 Su-Jin Kim GNU Sawing and saws ( 톱 ) A cutting operation where the tool consists of a series of small teeth that removes material. Belt sawDisk saw

34. Machining Manufacturing Processes © 2012 Su-Jin Kim GNU Turning ( 선삭 ) A piece of material is rotated and a single point cutting tool is traversed along 2 axes of motion to produce the cylinder, tubular components and various rotational geometries.

35. Machining Manufacturing Processes © 2012 Su-Jin Kim GNU Lathe ( 선반 ) Turning can be done manually, in a traditional form of lathe, which frequently requires continuous supervision by the operator.

36. Machining Manufacturing Processes © 2012 Su-Jin Kim GNU 1 st Korean Lathe

37. Machining Manufacturing Processes © 2012 Su-Jin Kim GNU CNC Lathe, Turning center Turning can be done by using a computer numerical control, known as CNC.

38. Machining Manufacturing Processes © 2012 Su-Jin Kim GNU Turning center Turning center has additional milling axis is called TurmMill ( 복합기 ) http://ma.gnu.ac.kr/vod/machining/TurnMill.AVI

39. Machining Manufacturing Processes © 2012 Su-Jin Kim GNU http://www.youtube.com/watch?v=tDc0l9Gm8D4 Turning process ( 선삭공정 ) Straight turning Taper turning Profiling (Couture turning) External grooving http://www.youtube.com/watch?v=5AB_etoHesI&p=9B6D9EAE75875D9D

40. Machining Manufacturing Processes © 2012 Su-Jin Kim GNU Math for Turning Cutting speed(mm/min) = 3.14 x Diameter x Spindle V = π D S MRR (Material Removal Rate) = Volume / Time = 3.14 x Diameter x Depth x Feed per revolution x Spindle Cutting time = Distance / (Feed per revolution x Spindle) V S S

41. Machining Manufacturing Processes © 2012 Su-Jin Kim GNU A 15.24-cm-long, 1.27-cm-diameter 304 stainless-steel rod is being reduced in diameter to 1.2192 cm by turning on a lathe. The spindle rotates at N=4000 rpm and the tool is travelling at an axial speed of 20.32 cm/min. Calculate the cutting speed, material-removal rate, cutting time, power dissipated, and cutting force. Solution Maximum cutting speed is Cutting speed at machined diameter is Depth of cut and feed is Ex) Turning

42. Machining Manufacturing Processes © 2012 Su-Jin Kim GNU Solution Material-removal rate is Actual time taken to cut is Amount of power dissipated is The torque and cutting force is Ex) Turning

43. Machining Manufacturing Processes © 2012 Su-Jin Kim GNU Milling Cutting tool is rotated and traversed along 3 axes of motion to produce from simple rectangular plane, slot, hole and complex contour.

44. Machining Manufacturing Processes © 2012 Su-Jin Kim GNU Milling

45. Machining Manufacturing Processes © 2012 Su-Jin Kim GNU Machining center (CNC Milling) Horizontal M/C Bridge TypeC Type Vertical M/C 5AX M/C http://www.youtube.com/user/GlacernMachineTools

46. Machining Manufacturing Processes © 2012 Su-Jin Kim GNU Huge 3+2 axis milling has additional rotation BC axis on head. Used for automobile door panel and bumper mold. http://ma.gnu.ac.kr/vod/machining/Huge_machine_tools.AVI http://ma.gnu.ac.kr/vod/machining/Huge_5axis.AVI 3+2 axis machining (5 면가공기 )

47. Machining Manufacturing Processes © 2012 Su-Jin Kim GNU 5-axis machining (5 축가공기 ) Has 2 tinting A C or B C axis on table or head. Rotary table: http://ma.gnu.ac.kr/vod/Machining/Rotaty_table.MP4http://ma.gnu.ac.kr/vod/Machining/Rotaty_table.MP4 Impeller : http://ma.gnu.ac.kr/vod/Machining/5axis_machining_impeller.MP4http://ma.gnu.ac.kr/vod/Machining/5axis_machining_impeller.MP4

48. Machining Manufacturing Processes © 2012 Su-Jin Kim GNU Automatic Tool Changer (ATC) Changer Arm Tool Spindle

49. Machining Manufacturing Processes © 2012 Su-Jin Kim GNU Automatic Pallet Changer (APC) Pallet #1 Pallet #2

50. Machining Manufacturing Processes © 2012 Su-Jin Kim GNU Work holding Vise, Clamp ( 치구 ) Work is fixed by vise or clamp on the table with T-slot Flex clamp: http://ma.gnu.ac.kr/vod/Machining/Clamp.MP4http://ma.gnu.ac.kr/vod/Machining/Clamp.MP4 http://www.youtube.com/user/GlacernMachineTools#p/u/5/J1VtofzVG24

51. Machining Manufacturing Processes © 2012 Su-Jin Kim GNU Tool holder, Tools Holder + Collet + Solid EndmillInsert Endmill http://www.youtube.com/watch?v=IPWGV_EGAHw&feature=related

52. Machining Manufacturing Processes © 2012 Su-Jin Kim GNU Tool holder, Tools

53. Machining Manufacturing Processes © 2012 Su-Jin Kim GNU Milling operations Face Cutter Basic: http://www.youtube.com/watch?v=j0vRYe9uvnIhttp://www.youtube.com/watch?v=j0vRYe9uvnI Face: http://www.youtube.com/watch?v=9OsNUi_o6C4http://www.youtube.com/watch?v=9OsNUi_o6C4 Endmill: http://www.youtube.com/user/GlacernMachineTools#p/u/1/HfIaISnqHOkhttp://www.youtube.com/user/GlacernMachineTools#p/u/1/HfIaISnqHOk Flat endmill (Slotting) Face cutter Endmill : Flat, Ball, Rounded

54. Machining Manufacturing Processes © 2012 Su-Jin Kim GNU Math for milling Cutting speed(mm/min) = 3.14 x Diameter x Spindle V = π D S Feed per tooth = Feed / (Spindle x Number of teeth) MMR = Depth x Width x Feed MRR = d w F ftft w d F (mm/min)

55. Machining Manufacturing Processes © 2012 Su-Jin Kim GNU Drilling Drills produces deep holes. Insert drill Drill: http://www.youtube.com/watch?v=ul20R32HJ3Ehttp://www.youtube.com/watch?v=ul20R32HJ3E Max drill Drilling machine Drill Drill: http://ma.gnu.ac.kr/vod/Machining/Drill.MP4http://ma.gnu.ac.kr/vod/Machining/Drill.MP4

56. Machining Manufacturing Processes © 2012 Su-Jin Kim GNU Tapping Tapping holder and tool Tapping Tap produces thread inside the hold. Tap Feed Rate = RPM x Pitch Ex) M6 x 1 at 2000 RPM = 2000 mm/min http://www.youtube.com/watch?v=vCHQLFZHHJc

57. Machining Manufacturing Processes © 2012 Su-Jin Kim GNU Reaming, Boring Reamer enlarges an hole to the diameter of the tool. Boring produce precise circular internal profiles. BoringReaming Drilling, Tapping, Boring: http://vimeo.com/8642433http://vimeo.com/8642433 http://www.youtube.com/user/GlacernMachineTools#p/u/0/om6GQKfoS1g

58. Machining Manufacturing Processes © 2012 Su-Jin Kim GNU Planer and Shaper

59. Machining Manufacturing Processes © 2012 Su-Jin Kim GNU Gear Hobbing A hob (cutter) is rotated one revolution to transfer each tooth profile onto a rotating gear blank. Used very often for medium to high sizes of production runs. http://www.youtube.com/watch?v=DwFssm9trSc

60. Machining Manufacturing Processes © 2012 Su-Jin Kim GNU Broaching Rotary broaching: http://www.youtube.com/watch?v=gUEcagEmmZo&p=9B6D9EAE75875D9Dhttp://www.youtube.com/watch?v=gUEcagEmmZo&p=9B6D9EAE75875D9D Linear broaching: the broach is run linearly against a surface of the workpiece to effect the cut. Rotary broaching: the broach is rotated and pressed into the workpiece to cut an axis symmetric shape. Broaching gear: http://www.youtube.com/watch?v=2K45B6tDqsg&p=9B6D9EAE75875D9Dhttp://www.youtube.com/watch?v=2K45B6tDqsg&p=9B6D9EAE75875D9D

61. Machining Manufacturing Processes © 2012 Su-Jin Kim GNU Design for milling Minimize machining, use casting and forging. Minimize the length to diameter ratio of the tools. Design features to be machined from one side.

62. Machining Manufacturing Processes © 2012 Su-Jin Kim GNU Design for milling The inside edges must have the radius of the end mill. For outside corners, chamfers are preferable over fillet. For flatness, bosses should be used. Ⓒ http://www.efunda.com/processes/machining/mill_design.cfm

63. Machining Manufacturing Processes © 2012 Su-Jin Kim GNU Economics of Machining Total cost per piece consists of four items: Cutting speed Cost Tool Setting up Machining Total

64. Machining Manufacturing Processes © 2012 Su-Jin Kim GNU References: Machine Tool Makers www.doosaninfracore.co.kr www.wia.co.kr www.hwacheon.co.kr www.mazak.jp (Japan)www.mazak.jp www.haascnc.com (USA)www.haascnc.com www.deckelmaho.com (EU)www.deckelmaho.com