Cutting Processes. Simulation Techniques in Manufacturing Technology Lecture 7

Transcription

1 Cutting Processes Simulation Techniques in Manufacturing Technology Lecture 7 Laboratory for Machine Tools and Production Engineering Chair of Manufacturing Technology Prof. Dr.-Ing. Dr.-Ing. E.h. Dr. h.c. Dr. h.c. F. Klocke

2 Outline 1 Introduction 2 Cutting processes with rotary motion 3 Cutting processes with parallel translation 4 Hard machining 5 Modeling of Machining Seite 1

3 Breakdown of the techniques involving a rotational main movement Turning Milling Boring Sawing work piece rotation translation - rotation work piecetranslation rotation translation rotation translation main movement main movement main movement main movement subsidiary movement sub. movement sub. movement sub. movement Seite 2

4 Breakdown of the techniques involving a translational main movement broaching multi teeth feed due to geometry high surface quality high accuracy high costs inflexible work piece planing Cutting motion by work piece Tool feed Stepwise, linear cutting motion Successive feed movement Machining of large, planar areas shaping Cutting motion by feed Stepwise, linear cutting motion Successive feed movement Machining of large, planar areas track Seite 3

5 Outline 1 Introduction 2 Cutting processes with rotary motion 2.1 Turning 2.2 Milling 2.3 Drilling 3 Cutting processes with parallel translation 4 Hard machining 5 Modeling of Machining Seite 4

6 Outline 1 Introduction 2 Cutting processes with rotary motion 2.1 Turning 2.2 Milling 2.3 Drilling 3 Cutting processes with parallel translation 4 Hard machining 5 Modeling of Machining Seite 5

7 Example: rough turning Source: Widia Seite 6

8 Example: finishing Source: Widia Seite 7

9 Terms at the cutting edge shank cutting direction rake face A γ feed direction minor cutting edge S minor flank face A α major cutting edge S major flank face A α corner radius Seite 8

10 Definition of the cutting edge angle κ r orthogonal plane P o reference Plane P r cutting edge plane P s Seite 9

11 Definition cutting edge angle κ r trace of the orthogonal plane P o trace of the cutting edge plane P S feed direction κ r r ε trace of the working plane P f reference plane P r Seite 10

12 Definition of the inclination angle λ s working plane P f cutting edge plane P S reference plane P r Seite 11

13 Definition of the inclination angle λ s trace of the working plane P f major cutting edge S λ s + - trace of the reference plane P r cutting direction cutting edge plane P S Seite 12

14 Definition of the rake angle γ Seite 13

15 Definition of the angles at the cutting edge trace of the reference plane P r trace of the rake face plane A γ γ o trace of the flank face plane A α expected cutting direction β o α o expected feed direction trace of the back plane P p orthogonal plane P o Seite 14

16 Tool variants in longitudinal cylindrical turning right hand side cutting left hand side cutting neutral Seite 15

17 Facing (DIN : ON ) cross face turning cross parting off longitudinal face turning Source: Sandvik Coromant Seite 16

18 Facing (DIN : ON ): cross / longitudinal face turning Seite 17

19 Facing (DIN : ON ): cross parting off Seite 18

20 Cylindrical turning (DIN : ON ) longitudinalcylindrical turning centreless rough turning cross-cylindrical turning Source: Iscar, Ceratizit Seite 19

21 Threatening (DIN : ON ) thread turning chasing tapping thread turning (external) thread turning (internal) Source: Garant, Seco, Ceratizit Seite 20

22 Profile turning (DIN : ON ) trepanning grooving cross-profile turning DIN Seite 21

23 Hob turning (DIN : ON ) Seite 22

24 Contour turning (DIN : ON ) NC-contour turning copy turning kinematiccontour turning NC gear reference formed part Source: Sandvik Coromant Seite 23

25 Internal turning skimming undercut cut in DIN Source: Iscar Seite 24

26 Internal turning s Source: Sandvik Seite 25

27 Outline 1 Introduction 2 Cutting processes with rotary motion 2.1 Turning 2.2 Milling 2.3 Drilling 3 Cutting processes with parallel translation 4 Hard machining 5 Modeling of Machining Seite 26

28 Milling processes DIN milling DIN slab / face milling circular milling helical milling hobbing profile milling form milling Seite 27

29 Face milling (DIN : ON ) Seite 28

30 Face milling (DIN : ON ) Seite 29

31 Slab milling (ON ): face- and peripheral milling face milling Workpiece surface is generated by face of the milling peripheral milling Workpiece surface is generated by peripheral surface of the milling v f P s n v f f z n ϕ a p κ r a e v c f z Seite 30

32 Up- and down milling down milling v c n f z up milling f z n F f F f F c a e F c v t Up- and down milling v t up milling part down milling part v t Seite 31

33 Tool-in-hand system: peripheral milling v f f z trace of P r v c a e ω E ω = ω c = 0 A ω E trace of P s P p P f P o Seite 32

34 Tool-in-hand system: face milling v f trace of P o ω A trace of P s n ω c κ r ω E ν f a p trace of P f n f z f z P r trace of P p a e trace of the entrance plane Seite 33

35 Contact conditions and cutting edge geometry in face milling f z a e a e2 C v c n C ϕ A -ε A n ϕ s ϕ a e1 v f +ε E entry plane f z φ=0 tangential plane cutting C-C cutting edge view A γ p contact types T U a p B b A B S b K n plane B-B b = a sin κ aei ϕ i = arccos D 2 p h ϕ = f z (f z << D) S S a V V a sin ϕ sin κ r Seite 34

36 Contact conditions depending on the radial and axial rake angle milling cutter γ f > 0 γ p > 0 S datum plane insert γ f > 0 γ p < 0 T γ f > 0 γ p = 0 T S S - contact T - contact ST - contact U γ f < 0 γ p < 0 γ f < 0 γ p > 0 V γ f = 0 γ p > 0 S V U - contact V - contact SV - contact Seite 35

37 Precision milling operations f z1 a p a p1 f z f z a p f z2 a p2 finish-milling no. of teeth 10 to 60 = 0.3 bis 1 mm a p f z = 0.3 bis 0.5 mm wide finish-milling no. of teeth 1 bis 6 = 0.05 to 0.2 mm a p f z = 0.5 bis 6 mm finish-milling with planing knives and wide finishing cutting edge no. of planing knives 20 to 30 no. of wide finishing cutting edges 1 to 2 finishing cutting edges a p1 = 0.5 to 2 mm = 0.1 to 0.3 mm wide finishing cutting edges f z1 a p2 f z2 = 0.03 to 0.05 mm = 2 to 5 mm Seite 36

38 Circular milling (DIN : ON ) a p n w n w n F n F v f vf additional axial cutting edges radial cutting edges n F Mill Source: Walter chipping space n W Seite 37

39 Helical milling (DIN : ON ) a b c d e f Seite 38

40 Hobbing (DIN : ON ) Tangentialvorschub rotation Fräserdrehung of hobb - rotation Werkraddrehung of Fräserdrehung Radialvorschub radial feed v c f a f w cutting speed axial feed hob feed Seite 39

41 Different types of hobs Monobloc gear hob Roughing-finishing multi hob Indexable insert hob high revolutions of the mill short milling times short first cut length Fotos: Fette, Saazor, Saacke high cutting ability rough- and finish milling easily to re-sharpen large gearing no sharpening low accuracy only for rough milling large gearing Seite 40

42 Profile milling (DIN : ON ) profile milling cutter gang milling cutter DIN Source: Sandvik Coromant, Ingersoll, ALESA AG Seite 41

43 Form milling (DIN : ON ) form-profile milling Source: Milltech, Dalscheid Seite 42

44 Outline 1 Introduction 2 Cutting processes with rotary motion 2.1 Turning 2.2 Milling 2.3 Drilling 3 Cutting processes with parallel translation 4 Hard machining 5 Modeling of Machining Seite 43

45 Drilling processes DIN drilling countersinking reaming DIN spot facing centre drilling tapping profile drilling form drilling Seite 44

46 Example of gun drilling Source: Widia Seite 45

47 Example of gun drilling Seite 46

48 Criteria for drilling Material separation and reaming at the major cutting edge Plastic deformation at the chisel edge Cutting speed drops down to zero in the centre of the drill Chips are difficult to remove Unfavourable heat distribution at the interface Reibung friction n f Bohrwerkzeug drill Reibung friction Werkstück Increased wear at the sharp-edged corner Reaming between leading lands and drilling wall Plastische plastic deformation Verformung Stofftrennung material seperation Seite 47

49 Cutting conditions dependent on drill diameter 0 1 mm 4 5 v c γ fe α fe drill radius r main cutting edge chisel edge m/min 10 0 Rake angle γ; clearance angle α cutting speed v c Seite 48

50 Fundamental kinematics: centre drilling γ f γ β cutting edge 1 α α xe η cutting edge 2 f f/2 cutting direction η effective direction feed direction Seite 49

51 Geometry of the cutting part of a twist drill cutting part plunge (lettering point) flat tang tapered shaft drill diameter d point length cutting length flute length plunge length cone length total length nach DIN Seite 50

52 Geometry at the cutting edge of a twist drill major Hauptschneide cutting edge Querschneide chisel edge α flank Freifläche face δ construction dimensions DIN 6539, Typ N diameter d: 1 mm drill-point angle σ: 118 major clearance angle α: 10 angle of twist : δ: 35 cutting material: grain size DK : HW-K µm Seite 51

53 Specific geometries of twist drills Form A Form B Form C Form D Form E cone shaped drill (basic polish for form A-D) pointed transverse cutting edge pointed cutting edge with corrected major cutting edge cross-wise polish pointed trans-verse cutting edge with facetted cutting edge corners point angle 180 with centre tip Seite 52

54 Twist drill for various materials Seite 53

55 Drilling processes I drilling: Cutting with circular primary motion. The axis of rotation of the and of the produced internal area are identical. The direction of the feed has the direction of this axis of rotation. centre drilling gun drilling tapping profile drilling primary motion feed motion primary motion feed motion primary motion feed motion primary motion feed motion source: DIN Seite 54

56 Gundrilling drill bushing cemented HM-Kopf carbide mit head eingeschliffenen with indexable inserts Führungsleisten Schaft shaft lubrication outlet cutting edge crimp Source: Sandvik Seite 55

57 Drilling processes II sinking: Drilling for producing planes which are orthogonal to the axis of rotation or rotationally symmetric cone and form planes. reaming: Bore up with a low undeformed chip thickness for producing better qualities of the surface. countersinking cylinder sinking reaming primary motion primary motion primary motion feed motion feed motion feed motion source: DIN Seite 56

58 Fundamental kinematics: centre drilling v f n minor cutting edge n trace of P r trace of P o web thickness v c major cutting edge trace of trace of P s P p ε r chisel edge σ κ = r 2 f z trace of a p 1 = D 2 P p h P r trace of P f σ a p P r b Seite 57

59 Outline 1 Introduction 2 Cutting processes with rotary motion 3 Cutting processes with parallel translation 3.1 Shaping/ Planing 3.2 Broaching 3.3 Sawing 4 Hard machining 5 Modeling of Machining Seite 58

60 Outline 1 Introduction 2 Cutting processes with rotary motion 3 Cutting processes with parallel translation 3.1 Shaping/ Planing 3.2 Broaching 3.3 Sawing 4 Hard machining 5 Modeling of Machining Seite 59

61 Definitions and kinematics planing/ shaping: Cutting with repeated parallel translation as primary motion and successive feed motion which is orientated orthogonal to the primary motion. The kinematics of planing and shaping are identical. When the primary motion comes from the the process is called planing, when the primary motion comes from the the process is called shaping. planing shaping primary motion at the primary motion at the Seite 60

62 Planing processes finish planing contour planing profile planing circular planing primary motion feed motion feed motion feed motion feed motion primary motion primary motion primary motion source: DIN Seite 61

63 Tool-in-hand system: planing trace of P s primary motion at the κ r v f trace of P f trace of Pp Pr trace of P o Seite 62

64 Outline 1 Introduction 2 Cutting processes with rotary motion 3 Cutting processes with parallel translation 3.1 Shaping/ Planing 3.2 Broaching 3.3 Sawing 4 Hard machining 5 Modeling of Machining Seite 63

65 Internal broaching s (schematic) A end piece shank way roughing- finishing- calibrating part(f z =0) f z t B bα 01 α01 α 02 γ 0 detail A detail B α 02 clearance angle b α01 width of chamber α 01 chamfer inclination t division γ 0 rake angle f z inclination Seite 64

66 Broaching processes I broaching: Cutting with a with more than one flute. The flutes are orientated one after another with the stepping of the undeformed chip thickness. The feed motion is substituted by the stepping. The last flutes of the produces the desired profile of the. After one run, the is ready and the surface finished. plane broaching external broaching internal broaching primary motion feed motion primary motion feed motion feed motion primary motion source: DIN Seite 65

67 Broaching processes II profile broaching helical broaching cylindrical broaching feed motion primary motion feed motion primary motions primary motions initial shape of the end shape of the source: DIN Seite 66

68 Tool-in-hand system: internal broaching feed motion is realized with the stepping flutes v f P f P o v c 4 f z a p trace of P r primary motion t z trace of P s P p and s Seite 67

69 Outline 1 Introduction 2 Cutting processes with rotary motion 3 Cutting processes with parallel translation 3.1 Shaping/ Planing 3.2 Broaching 3.3 Sawing 4 Hard machining 5 Modeling of Machining Seite 68

70 Sawing processes sawing: Cutting with circular motion or parallel translation as primary motion. The Tools have more than one flute. The depth of cut is low and the primary motion comes from the. feed motion hack sawing primary motion band sawing primary motion circular sawing feed motion primary motion feed motion source: DIN Seite 69

71 Terms and cutting part geometry of the sawing belt width base of a gear tooth t R tooth head g 0 b 0 H a 0 tip of tooth tooth gap belt saw h v c v e working plane 90 o f z back of belt cutting part (chip space) a e t tooth division v c cutting speed R base radius v e operating speed H tooth height f z a e tooth feed width of cut Seite 70

72 Tool-in-hand system: hack sawing primary motion feed motion trace of P r v f f z trace of P s P p P f P o κ r trace of P f P o Pr trace of P s P p Seite 71

73 Outline 1 Introduction 2 Cutting processes with rotary motion 3 Cutting processes with parallel translation 4 Hard machining 5 Modeling of Machining Seite 72

74 Hard machining with geometrically defined cutting edges Techniques turning milling broaching Cutting materials ultra fine grained carbides ceramics PCBN Technological specialties cutting process is conducted by a single or a few cutting edges strong relation between the condition of single cutting edges and the surface rim zone of the, because the materials are hard and thus the s posses a high wear risk risk of white layers Seite 73

75 Mechanically strong steel parts need to be hardened / tempered Hardening steel leads to mechanically strong parts Soft Micro structure: ferrite Hardness: HRC Hardening / Tempering Hard Micro structure:martensite Hardness: HRC Stress s Stress s Strain e Material volume: 100 % Strain e Material volume: approx. 103 % non-uniform strain and distortion => Final cut necessary to achieve high accuracy in form and size, small and medium parts need to be oversized by approx mm Seite 74

76 Typical parts for hard machining Cams shaft Slipping load (e.g. contact with bucket tappet) Bearing rings Rolling load (contact with rollers) Micro slipping (Contact with shaft) Gears Rolling load (Contact with partner gear) Bending load (at tooth ground) Slipping load (Contact with synchronising ring) Seite 75

77 Hard machining, turning and grinding Hard machining can be realised by defined and undefined machining principles. Hardened steel can only be cut defined if the material in front of the cutting tip is heated and softened by the process itself. This leads to special requirements for the cutting material and the press design. Seite 76

78 Application for Precision Hard Turning 100 % Machining time 100 % Machining Cost 90 % 90 % 80 % 80 % 70 % 70 % 60 % 60 % 50 % 50 % Part: Precision profile roller O 150 mm 40 % 30 % 40 % 30 % Material: Machining: X210CrW12 hardened (63 HRC) Hard turning of the profile 20 % 10 % 20 % 10 % Grinding Hard Turning Grinding Hard Turning Seite 77

79 Outline 1 Introduction 2 Cutting processes with rotary motion 3 Cutting processes with parallel translation 4 Hard machining 5 Modeling of Machining Seite 78

80 Force calculation: time function Substitution of the empirical force equation proposed by Kienzle with the technical terms: F i = k i1.1 b h 1 m i equation proposed by Salomon or Kienzle F i diameter of the a p π D v f k i 1.1 sinω sinκ r sinκ r z vc ( 1 ) number of teeth polar coordinate m i source: Diss. Rehse h max f z sinκ sinω a p b = sinκ r r Question: What is the angle ω? ω = 2 b ) D ) b = v c t df i k discretisation of the equation: a π D v 2 v dt p f c i1.1 sin sin sinκ r z vc D κ r ( 1 ) m i basement for modeling Seite 79

81 Force calculation: technical terms df i k discretisation of the equation: a π D v 2 v dt p f c i1.1 sin sin sinκ r z vc D κ r ( 1 ) m i Solving the equation for discrete times discrete time function discrete force components (dt) df i force in x / N time / sec calculated measured addition of the force components in x- and y- direction separately The same procedure for the other flutes! transformation of the force components into the x- and y- direction Seite 80

82 Penetration calculation: peripheral milling data of the machine data of the data of the matrix model for the penetration calculation feed velocity vector field for representation the vector field for representation the thickness of cut h width of cut b Seite 81

83 Thank you for your attention!! Seite 82

84 Outline 1 Introduction 2 Cutting processes with rotary motion 3 Cutting processes with parallel translation 4 Hard machining 5 Modeling of Machining Seite 83

85 Outline 1 Introduction 2 Cutting processes with rotary motion 3 Cutting processes with parallel translation 4 Hard machining 5 Modeling of Machining Seite 84

86 Process classification Manufacturing Processes 1 primary shaping 2 secondary shaping / forming 3 cutting 4 joining 5 coating 6 changing material properties 3.2 cutting turning drilling reaming milling planing shaping broaching sawing filing rasping brushing scraping chiselling rotary motion parallel translation source: DIN Seite 85

87 Evaluation Attend: knowledge of the complete design (angel ω) if the information is not available the modeling cannot success! advantages general model possibility to use general software possibility to expand with dynamic terms mathematical formulation disadvantage no direct material information This information is contained in the specific force parameter! Seite 86