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Additive Manufacturing Patrik Hoffmann
Laboratory for Advanced Materials Processing Feuerwerkerstrasse 39, 3602 Thun
Laboratory for photonic materials and characterization, LPMAT,
STI, EPFL, Station 17, 1014 Lausanne, Switzerland
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Laboratory for Advanced Materials Processing (Head: Prof. P. Hoffmann)
AdditiveManufacturing
AlloyDesign/Optimization
Powder supplyPowder modification
recycling…
Real time process
observationhigh speed IMAGING
spectroscopyacoustic emission
…
Beam basedprocessing
LaserElectron beam
Microwaves…
Alloy Design for Advanced Processing Technologies Group (Dr. C. Leinenbach)
Processing Dynamics Group (Dr. K. Wasmer)
Nanoparticles and Nanocomposites Group (Dr. M. Leparoux)
Beam processing and Coatings Group (Prof. P. Hoffmann)
Research Groups
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Beam induced 3-D printing of metal Powder bed Direct Laser deposition
Laser Powder Deposition Productivity Large devices Geometrical limitations Powder
Laser Wire Deposition
Clean & productive 100% materials use Geometrical limitations Materials limitations
Selective Laser Melting (SLM)
Complex geometries Precision Speed Reproducibility Powder recycling
Electron Beam Melting (EBM)
High performance materials complex geometries Precision Reproducibility Powder recycling Vacuum
http://www.arcamgroup.com
http://www.turpro.de
http://www.iws.fraunhofer.de
http://www.tms.org
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State of the art of metal AM – most critical: powder
powder particle diameter > 20 um (flowability) Fe, Ti, Al, Mg, CoCr, Ti6Al4V, 316L, …
Geoff Booth, TWI, Paper presented at IIW Annual Assembly, Osaka, Japan, 11-16 July 2004
layer thickness 20 – 100 um
powder jet Direct Metal Deposition
powder bed Selective Laser Melting
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Powder bed - Selective Laser Melting
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Powder bed - State of the art of powder bed metal AM machines
Laser e-beam
focused to > 70 um diameter (200 um) < 180 um up to 7 m/ s beam speed (0.1 - 2 m/ s) < 8 m/ s Fiber laser with power 50 – 400 W (200 W) 4 kW
Sources: EWI report 2011, KTH PhD 2012, tens of WEB pages
Renishaw 250
50 mm3/s tolerance 200 um
10 mm3/s tolerance 50-100 um
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R & D best of: ILT Aachen – Wilhelm Meiners, … 2013, Rapid Prototyping Journal,19, 51; 1064 nm, cw, 48 - 60W, diameter 200 µm; 200 mm/s, preheating 1670°C; layer thickness 50 µm; ~100kW/cm2
Flexural strength reached so far: 530 MPa (other methods 2400 MPa)
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Powder jet - Laser assisted generating techniques
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Powder bed versus Powder jet
Powder bed
Advantages: Process control – simpler 10 mm3/s tolerance 50-100 um Disadvantages: No materials gradients
Powder jet
Advantages: Materials gradients – alloys 16 - 100 mm3/s Disadvantages: Powder jet size large
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Expectations in industry for AM in production
Productivity and surface quality Increase of productivity (by factor of 10) Decrease of surface roughness Decrease in post-treatment(s) Quality control Reproducibility – process reliability In-process QC Automization Reduction of manual work Combination with other processes – production integration
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Process in more detail
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Simulation results for powder bed AM
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Simulation results for powder bed AM
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Laser beam hits molten material ! Heat flow determines process speed (nothing else !) How deep does laser beam reach ? How fast does heat flow through material ?
0.5 ms 2.5.106 W/ cm2
I. Yadroitsev et al., J. Mater. Proc. Tech. 210 (2010) 1624–1631
Process in more detail
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D. Bäuerle; Laser Processing and Chemistry, 4th ed. Springer, Berlin, 2011
Laser materials processing: It depends on : 1) time scale of the
process 2) intensity you need for
the process
Parameters for laser materials processing
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Process in more detail
Intensity needed at 200W with 100 µm beam Ø 2.5 106 W/cm2
Bäuerle: 104 – 105 W/cm2
Speed at 1 m/s with 100 µm beam Ø residence time: 0.1 ms Bäuerle: 1 ms
Heat flow determines process speed In
ten
sity
[W
/cm
2]
time [s]
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Absorption threshold
Rapid dramatic increase of absorptivity with increasing intensity – fluctuations of thermal environment !
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Diagram – speed – power – dwell time La
ser p
ower
[W]
Scan speed [m/s]
Ø = 200 µm
Ø = 100 µm
Ø = 50 µm
laser power afo beam speed keeping constant intensity (2.5.106W/cm2) and dwell time (0.1 ms)
0
100
200
300
400
500
600
700
0.0 0.5 1.0 1.5 2.0
Ø = 10 µm needs 2 W !
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Process limitations: Powder bed versus Powder jet
Powder bed Structures precision: Powder layer thickness = lateral dimensions > 20 µm
Powder jet Structures precision: Powder jet size > 200 µm
Max speed determined by melting bath speed Thermal stress resistance of material (relaxation by post treatment)
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Quality – process speed relation
Side wall roughness – tolerances - particle diameter 2 x particle diameter layer thickness Beam diameter / speed = dwell time (0.5 ms) e.g.: 100 µm / 0.2 m/s Intensity limitation: 2.5.106 W/cm2 otherwise drilling,
ablation
Finer powder, thinner layer thickness, same beam diameter, 50 µm; 2 m/s; same total speed !
Quality can be improved with finer powder, no speed gain. Attention limit is due to very fast cooling rates – glazing
effect (amorphous material – brittle)
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Laser additive manufacturing
Quality determining parameters Materials Heat flow (thermal stress, cracks, bubbles, spatter, pores, …) Laser power, scan speed, beam diameter (not limited !!) Powder particle size and distribution Laser wavelength (only important for Ag, Cu, Au) Laser beam movement (scanning strategy, …) Laser pulse duration (intensity modulation for cw lasers) Laser beam intensity distribution ….
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Laser additive manufacturing
Outlook
