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Institut für Werkzeugmaschinen und Betriebswissenschaften Prof. Dr.-Ing. M. Zäh Prof. Dr.-Ing. G. Reinhart DETERMINATION OF PROCESS PARAMETERS FOR ELECTRON BEAM SINTERING (EBS) Hannover, November 6th 2008 European Comsol Conference Dipl.-Ing. Markus Kahnert Presented at the COMSOL Conference 2008 Hannover

DETERMINATION OF PROCESS PARAMETERS FOR ELECTRON … · 2009. 1. 29. · Beam=const. electron beam liquid system boundary phase 1 preheated powder phase 2 heat input phase 3 liquid

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Text of DETERMINATION OF PROCESS PARAMETERS FOR ELECTRON … · 2009. 1. 29. · Beam=const. electron beam...

  • Institut für Werkzeugmaschinenund BetriebswissenschaftenProf. Dr.-Ing. M. ZähProf. Dr.-Ing. G. Reinhart

    DETERMINATION OF PROCESS PARAMETERS FOR ELECTRON BEAM SINTERING (EBS)

    Hannover, November 6th 2008European Comsol Conference

    Dipl.-Ing. Markus Kahnert

    Presented at the COMSOL Conference 2008 Hannover

  • 12.11.2008 Seite 2© iwb 2008

    1. Introduction – Electron Beam Sintering (EBS)2. Objective of the present work3. Mathematical model

    - Overview- Heat Source Model- Material Properties

    4. Numerical Model5. Simulation Results and Discussion6. Conclusion

    Outline

  • 12.11.2008 Seite 3© iwb 2008

    1. Introduction – Electron Beam Sintering (EBS)2. Objective of the present work3. Mathematical model

    - Overview- Heat Source Model- Material Properties

    4. Numerical Model5. Simulation Results and Discussion6. Conclusion

    Outline

  • 12.11.2008 Seite 4© iwb 2008

    Electron beam sintering

    Electron Beam Sintering

    electron beam generator

    electron beam

    building volume

    building plate

    building volumewith metal-powder

    sintered layer

    building plate

    part

    preheatedarea

    new layer ofmetal powder

    divergence of the electron beam

    focusedelectron beam

    sinteredlayer

    re-coating preheating scanningwith different

    strategies

  • 12.11.2008 Seite 5© iwb 2008

    Electron Beam Sintering (EBS)

    Potentials of the electron beam

    High beam power and energy densityFast, massless beam deflection„Quasi-simultaneous“ beam exposureUniform insertion of energyOpen configurable beam figures

    Vacuum chamber

    Beam generator

    Mechanical pumps

  • 12.11.2008 Seite 6© iwb 2008

    1. Introduction – Electron Beam Sintering (EBS)2. Objective of the present work3. Mathematical model

    - Overview- Heat Source Model- Material Properties

    4. Numerical Model5. Simulation Results and Discussion6. Conclusion

    Outline

  • 12.11.2008 Seite 7© iwb 2008

    Objective of the present work

    Process stability• Metal parts production• Two major deficiencies can be observed

    - Balling- Delamination

    Process cannot be examined due to accessibility and resolution of thermography unit

    Understanding of the process needs to be enhanced

    Analysis of the beam-material interaction by means of FEA

    Balling

    Delamination

  • 12.11.2008 Seite 8© iwb 2008

    1. Introduction – Electron Beam Sintering (EBS)2. Objective of the present work3. Mathematical model

    - Overview- Heat Source Model- Material Properties

    4. Numerical Model5. Simulation Results and Discussion6. Conclusion

    Outline

  • 12.11.2008 Seite 9© iwb 2008

    Mathematical Model

    Overview

    MathematicalModel

    FEM-Simulation

    Resultanalysis

    Knowledge to use in real process

    Powderproperties

    Temperatur [K]

    Zeit [s]

    Validation

    time [s]

    temperature [K]

    0

    20

    40

    60

    80

    273 773 1273 1773Temperatur [K]

    heat conductivity [W/(mK)]

  • 12.11.2008 Seite 10© iwb 2008

    time=0.002 isosurface: heat source [W/m³]

    Heat Source Model

    • Horizontal intensity according to a Gaussian distribution

    • Vertical intensity follows a 2nd degree polynom

    • Power efficiency: 78%

    • Superposition

    • Penetration depth at given accelerating voltage and powder density: 62 µm

    • Moving Heat Source at constant velocity

    Mathematical Model

  • 12.11.2008 Seite 11© iwb 2008

    Temperature Dependence of Material Properties

    0

    20

    40

    60

    80

    273 773 1273 1773Temperatur [K]

    heat conductivity [W/(mK)]

    0,980,940,860,830,810,80,78ε

    13961208755680569481333T [K]

    emissity of metal powder

    • Thermomechanical properties of metal powders are not common knowledge due to trade secrets and multitude of powders

    • Experiments and analytical models available

    • Heat capacity is similar to that of massive material

    • Heat conductivity and emissivity modelled and validated

    Mathematical Model

  • 12.11.2008 Seite 12© iwb 2008

    1. Introduction – Electron Beam Sintering (EBS)2. Objective of the present work3. Mathematical model

    - Overview- Heat Source Model- Material Properties

    4. Numerical Model5. Simulation Results and Discussion6. Conclusion

    Outline

  • 12.11.2008 Seite 13© iwb 2008

    Numerical Model

    Numerical Model

    solidified material

    powder material

    model lengthtrace widthpowder layerthickness

    electron beam(Ib, Ua, vs)

    powder(tl, υp )

    hatch distance h

    x

    yz

    solid materialmelt line

    Square to bemeleted

    beam spotdiameter db

    Part

    Scanning pattern

    Model

    Meshed modelThermal analysis

  • 12.11.2008 Seite 14© iwb 2008

    1. Introduction – Electron Beam Sintering (EBS)2. Objective of the present work3. Mathematical model

    - Overview- Heat Source Model- Material Properties

    4. Numerical Model5. Simulation Results and Discussion6. Conclusion

    Outline

  • 12.11.2008 Seite 15© iwb 2008

    Simulation Results and Discussion

    Objective of the Simulation

    0.1 mmhhatch distance

    0.1 m/svsscan speed

    1353 Kυppreheating temperature

    100 µmtllayer thickness

    200 µmdbbeam spot diameter

    1 mAIbbeam current

    100 kVUaaccelerating voltage

    ValueVariableProcess parameter

    1.0·10-04 mpowder layer thickness

    2.0·10-03 mmodel length

    2.0·10-04 mtrace width

    6.2·10-05 mSEB penetration depth

    ValueVariableModel parameter

    Starting Conditions and Process Parameters

    • Calculation of the size and shape of the melt pool

    • Simulation of the heat distribution within one melt line

    Powder: 3.4 g/cm³Massive: 7,9 g/cm³

    Density

    20-63 µmGrain Size

    316L (1.4404)Material

    ValueMaterial parameters

  • 12.11.2008 Seite 16© iwb 2008

    Simulation Results and Discussion

    Heat distribution within one melt linetemperature [K] @ various depths

    x=0 m; y=1*10-3 m; z=0 mx=0 m; y=1*10-3 m; z=-1*10-4 mx=0 m; y=1*10-3 m; z=-2*10-4 m

    • Simulation of the transient temperature distribution in the center of a melt line at various depths

    • Complete melting of a layer at point z=-1*10-4 m (= layer thickness)

    • After the powder has reached melting temperature, the layer thickness decreases proportional to its density increase

    TS= 1699 K

  • 12.11.2008 Seite 17© iwb 2008

    Simulation Results and Discussion

    Calculation of the size and shape of the melt pool

    L/W=3.8

    mm

    time=0.002 sisosurface: temperature [K]

    solid

    vBeam=const.electronbeam

    liquid

    system boundary

    phase 1preheated powder

    phase 2heat input

    phase 3liquid

    phase 4phase change

    phase 5solid

    solid

    vBeam=const.electronbeam

    liquid

    system boundary

    phase 1preheated powder

    phase 2heat input

    phase 3liquid

    phase 4phase change

    phase 5solid

    • Calculation of the Size and shape of the melt pool according to real process parameters

    • L/W-ratio is 3.8, no balling observed

    • in comparison: 2.1 in laserbeam-based processes (SLM, DMLS, etc.)

    • Possible reasons:- preheating temperature- vacuum in the process area- different beam-material interaction

    • Research efforts to be done

  • 12.11.2008 Seite 18© iwb 2008

    1. Introduction – Electron Beam Sintering (EBS)2. Objective of the present work3. Mathematical model

    - Overview- Heat Source Model- Material Properties

    4. Numerical Model5. Simulation Results and Discussion6. Conclusion

    Outline

  • 12.11.2008 Seite 19© iwb 2008

    Conclusion

    Manufacturing of EBS parts only possible with considerable process knowledge

    Simulation carried out in order to evaluate necessary beam power and other process parameters

    FE-Modelling of the energy input based on a mathematical abstracted heat sourceand a discretized powder bed is an effective tool

    Differences between Laser- and Electron Beam-based processes discovered

    Model can be transferred to alternative additive layer manufacturing technologies

  • Institut für Werkzeugmaschinenund BetriebswissenschaftenProf. Dr.-Ing. M. ZähProf. Dr.-Ing. G. Reinhart

    Dipl.-Ing. Markus Kahnert

    Telefon +49 (0) 821 / 5 68 83 - 33 Telefax +49 (0) 821 / 5 68 83 - 50 E-Mail: [email protected]

    Adresseiwb Anwenderzentrum AugsburgBeim Glaspalast 586153 Augsburg www.iwb-augsburg.de

    Kontakt:

  • 12.11.2008 Seite 21© iwb 2008

    Requirements in production technology

    innovative technologies for an economicmanufacturing of complex parts (powder based manufacturing methods – SLM, DMLS, EBS)

    wide range of processable materials (high quality steel, titanium alloys, aluminum alloys)

    efficient numerical methods for virtual design of manufacturing processes – Finite-Element-Analysis (FEA)

    customized, complex products

    powder based manufacturing processes

    engine componentmold insert for injection dies

    source: ConceptLaser

    source: DaimlerChrysler

    Mega-trends:Demand for individualization of products increases (“mass customisation”)Products become more complexLife cycles shorten