Prof. C. Sommitsch J. P. H. Zamaniα 6nkT R 6σ WT, 6 mm 4expaT ` A (MPa) B (MPa) C m n T k(°C) a b...

Institute of Materials Science and Welding

DI HZ Turin‐Italy, 13‐14 June 2013 14th CIRP CMMO

Prof. C. SommitschDr. B. SondereggerDI J. P. HermaniDI H. Zamani

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Overview

Laser Assisted Milling Experimental Procedure Resulting Force Reduction 3D FEM of Laser Assisted Machining Model Validation Summary

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Technology Supplier

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Laser Assisted Milling

Objective

Approach

Implementation

Reduction of tool wear and increasing material removal rate

Reduction of process forces

Reduction of material strength using laser heating of chip volume

Previous Approach

Novel Approach

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Working principle of the Novel Laser Assisted Milling

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Tool principle of the Novel Laser Assisted Milling

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Process Control Parameters

Cutter rotation axis

Laser control

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Laser Heat Source Modeling

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Time Depending Laser Power (Video)

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The Modeling of Incident Angle

V=100 m/minIncident angle= 0 °Power = 1000 W

=0.44


=0.67


=0.49

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Absorption Coefficient

Approach: Irradiation of Ti‐6Al‐4V workpiece without tool

engagement at different laser powers Cutting velocity: 25 m/min (331 rpm) Feed=50 µm/rev Determination of max. temperature by

means of depth and kind of microstructure

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Absorption Coefficient

I. initial microstructure (α+β)II. no martensitic transformation but β transformation from αIII. partial martensitic transformationIV. complete martensitic transformationV. oxide layer and white surface layer

Estimated absorption coefficient (α):0.27 ± 0.03

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Thermal Model Validation

V=25 m/minFeed=50 µm/revPower = 1250 Wα = 0.23

V=25 m/minFeed=50 µm/revPower = 1071 Wα = 0.23

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Laser Assisted Milling (Video)

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Process Forces and Tool Wear

F_X = 0,0004x + 46,343

F_Y = 0,0026x + 111,73

F_Z= 0,0038x + 77,161

0

20

40

60

80

100

120

140

160

0 2000 4000 6000 8000 10000

Cut

ting

Forc

e (N

)

Material removal volume (mm³)

F_X F_Y F_Z

F_X= 0,0004x + 41,167

F_Y = 0,0021x + 81,348

F_Z = 0,0026x + 73,753

0

20

40

60

80

100

120

140

160

0 2000 4000 6000 8000 10000

Cut

ting

Forc

e (N

)

Material removal volume (mm³)

F_X F_Y F_Z

The effect of milling time on the process forces and flank wear

V=50 m/minFeed=70 µm/revPower = 0 WLaser advance= 6 mm

V=50 m/minFeed=70 µm/revPower = 1428 WLaser advance= 6 mm

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Process Forces

40

60

80

100

120

140

160

40 60 80 100

Forc

e_ Y

[N]

Feed rate fz [µm/rev]

40

60

80

100

120

140

160

40 60 80 100

Forc

e_ Y

[N]


40

60

80

100

120

140

160

40 60 80 100

Forc

e_ Y

[N]


PL = 0 W

PL = 536 W

PL = 714 W

PL = 893 W

PL = 1071 W

PL = 1250 W

PL = 1428 W

PL = 1607 W

PL = 1785 W

The effect of cutting velocity on the main cutting force at different laser powers

cutting velocity 25m/min



Absolute value of force reduction decreases with cutting velocity

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3D FEM of Laser Assisted Milling

Material

Conductivity(W/mK)

Part (Ti6Al4V)

25 °C500°C900°C995°C1100 °C 1650°C

712.620.219.32128.4

Tool (TiAlN‐coated cemented carbide)

25°C1000°C

1220

heat capacity (J/Kg °C)

Part (Ti6Al4V)

25°C500°C900°C995°C1100°C1650 °C

546651734641660759

Tool (TiAlN‐coated cemented carbide)

598

Contact areaheat transfer coefficient (kW/m²K) 50

Friction coefficient

Environment Forced convection (Air jet cooling,Overhead) (W/m²K)

2000

Milling condition

Cutter RDHX 0702 MOT

Cutting width(mm) 8

Rake angle (° ) 11

Nose radius(mm) 0.02

Depth of cut (mm) 0.5

Cutting velocity(m/min) 25, 50, 75, 100

Feed (mm/rev) 0.05, 0.07, 0.09

Laser power (W) 536, 714, 893, 1071, 1250, 1428

Video

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3D FEM of Laser Assisted Milling

Modified (TANH) Johnson‐ Cook

Johnson‐ Cook

A (MPa) B (MPa) C m n a b c d e

Modified JC‐model [Sima et al ,2010]

724 683.2 0.035 1.0 0.47 1660 2 1 2 1 0.05

b

a

S

c

DModified JC

JC

Effective strain

Equivalent stress

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2D Chip Formation

V=0.005 m/sFeed=100 µm/revRake angle= 0 °Power = 0 W

V=5 m/sFeed=100 µm/revRake angle= 0 °Power = 0 W



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Nonlinear Thermal Softening (NTS)

σ A Bε 1 Clnεε 1

T TT T

εαnk T

R σ T ,

m m exp aT

A (MPa) B (MPa) C m n T (°C) a b m α

Modified JC-model 724 683.2 0.035 1.0 0.47 1660 10 2.9 1 10

Johnson‐ Cook

Minimum strain rate (ε ) for occurrence of adiabatic shear (a simplification for 3D modeling)

Nonlinear thermal softening at high strain rates

Johnson‐ Cook

Critical strain

Flow stress degradation

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2D Chip Formation (NTS)


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3D Model validation

65 63

53 5652

53 5451

40 3937 36 36 35

55

4440

39 37

34 32

0

10

20

30

40

50

60

70

0 893 1071 1250 1428 1607 1758

Forc

e_X

[N]

Laser Power (W)

V=50 m/min, Feed=90 µm/revEXP SIM_HYP SIM_NTS

150

120108

99

9077

84

135

110105

101 98 96 95

152

116 109103

93 88 85

0

20

40

60

80

100

120

140

160

0 893 1071 1250 1428 1607 1758

Forc

e_Y

[N]

Laser Power (W)


100

85

68 69 65

79

10395

79 76 74 72 71 70

100

8380 77

72 71 68

0

20

40

60

80

100

120

0 893 1071 1250 1428 1607 1758

Forc

e_Z

[N]

Laser Power(W)


• The amount of predicted force reduction with increasing the laser power in X direction is higher than the experimental results

• An excellent agreement for cutting forces in Y‐direction was found for the used model • The forces in Z‐direction showed a very good agreement for laser powers up to 1428W

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Summary

Review: Presentation of novel laser assisted milling Results of laser‐assisted milling of Ti‐6Al‐4V using TiAlN‐coated cemented carbide cutting

insert in different cutting conditions Reduction of force in X‐direction up to 25%, Y‐direction up to 60% and Z‐direction up to 65% Low level of tool wear according to the milling time 3D‐FEM simulation Integration of time depending laser power in machining simulation Model validation for machining of Ti6Al4V at different cutting conditions (TANH and NTS)

Outlook: Expand the milling material spectrum Increasing the machining productivity

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Acknowledgements

The research work is part of the TooLAM project,funded by the European Union and the

Austrian Research Promotion Agency (FFG)

within the EraSME program.

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Thanks for your attention

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Prof. C. Sommitsch J. P. H. Zamaniα 6nkT R 6σ WT, 6 mm 4expaT ` A (MPa) B (MPa) C m n T k(°C) a b...

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