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© inspire irpd – a joint project with university of applied science St. Gallen
Commercial SLS powders
- state of the art and recent developments -
Manfred Schmid*, Gideon N. Levy§§§§
* inspire AG, irpd, CH-9014 St. Gallen§§§§IPL, CDRsp 2411-901 Leiria, Portugal
2013 Annual Additive Manufacturing Users Group Conference , Jacksonville, Florida, April 17, 2013
© inspire irpd – a joint project with university of applied science St. Gallen
� IntroductionInstitute inspire-irpd, plastics pyramid
� SLS-Powders – combination of propertiesparticle distribution, thermal behavior, rheology, aging
� SLS-Powders – ‘state of the art’market, current assortment, basic properties
� SLS-Powders – ‘recent developments - near future’
� Summary
Agenda
Materials flexibility in Rapid Manufacturing (RM), …, has been a critical factor in the technology from the very beginning.
D.L. Bourell (2006, University Austin, TX)
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© inspire irpd – a joint project with university of applied science St. Gallen
Competence centre for the Swiss Industry regarding production technique and tooling .
Founded on an initiative of ETH-Zürich and machine building industry . Approved as ETH-research annex institute (non-profit foundation).
© inspire irpd – a joint project with university of applied science St. Gallen
research institute with production facility � service bureau!Introduction: irpd
customer feedback
fit for Industry
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© inspire irpd – a joint project with university of applied science St. Gallen
PA, PET, POM
marketshare:
~1%
~5%
~94%
PE, PP, PS, PMMA
HP –Plastics Use (°C): 160-260price: > 15 $/kg
Engineering PlasticsUse (°C): < 140price: 5 to 10 $/kg
Standard PlasticsUse (°C): < 90price: < 2 $/kg
amorphous partially crystalline
pric
e&
per
form
ance
Plastics pyramid: properties, quantity, price
© inspire irpd – a joint project with university of applied science St. Gallen
Plastics pyramid: reality for SLS
HP –Plastics : PEK
EngineeringPlastics
StandardPlastics
: PA12 , PA 11
: PP, TPE, PS
price: > 500 $/kg
price: 60 - 100$/kg
price: 60 - 200 $/kg
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© inspire irpd – a joint project with university of applied science St. Gallen
SLS-Powders – combination of propertiesparticle distribution, thermal behavior, rheology, aging
Why is it so complicate to make a new SLS powder?
or
© inspire irpd – a joint project with university of applied science St. Gallen
5 main topics:
> Particle- spherical- smooth surface
> Powder- distrib. (20-80 u)
> Optical properties- absorption 10.6 u
> Thermal behavior- sintering window
> Rheology- low zero viscosity
influences on SLS materials
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© inspire irpd – a joint project with university of applied science St. Gallen
SLS-materials:thermal properties
Curling
© inspire irpd – a joint project with university of applied science St. Gallen
mW10
°C120 130 140 150 160 170 180 190 200 210
exoexoexoexo
INSPIRE, irpd: ThermoanalyseINSPIRE, irpd: ThermoanalyseINSPIRE, irpd: ThermoanalyseINSPIRE, irpd: Thermoanalyse System System System SystemeeeeRRRRTATATATAMETTLER TOLEDO SMETTLER TOLEDO SMETTLER TOLEDO SMETTLER TOLEDO S
SLS Sintering Window :
∆T=(Tm-Tc)onset
Metastable area with two phases
Tmonset
Tmpeak
Tcpeak
Tconset
Heating
Cooling
∆Hm
∆Hc
� Wide Sintering Window
� High melting enthalpy
� Narrow melting region
Spe
cific
Hea
t Flo
w [W
/g]
Temperature [°C]
Differential Scanning Calorimetry
Constant heating/cooling rate:
10°C/min
Characterization Methods: DSC
� Semi-crystalline Thermoplastics (PA12, PA11, PP, coPP, PEEK)
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Ts
Lateral growth and curling trade off with part
bed temperature
Lateral growth
Curling
∆∆∆∆T Part bed:
5°°°°C !
Characterization Methods: DSC
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SLS-materials:rheological properties
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© inspire irpd – a joint project with university of applied science St. Gallen
Polymer: melt viscosity
Melt viscosity (η) of polymers is highlycomplex as polymers are viscoelastic ;
η of pure polymers depends mainly on:- molecular weight (chain length)- shear stress- temperature
visc
osity
shear rate
deformationof molecules
PA12 low viscosity PA12 middle viscosity
no shear stress during SLS processing except gravity!
© inspire irpd – a joint project with university of applied science St. Gallen
Y
X
Orange peel effect increase with MFI reduction
Production Batch MFI=54 g/10min
Test H+J MFI=42 g/10min
Test Reference MFI=27 g/10min
SLS-materials: rheological properties
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© inspire irpd – a joint project with university of applied science St. Gallen
Polymerisates: no reactive chain endgroups
Polycondensates: still active end groups(-NH2 and -COOH in case of polyamides)
post condensation during SLS processing
increasing chain length
increasing melt viscosity
PA12: ring opening polyaddition of Laurinlactam: H--N-(CH2)11-C--OH
SLS-materials: rheological properties / aging
H
O
n
= reactive end groups -NH2 and -COOH
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H-[-NH-(CH2)11-CO-]x-OH + H-[-NH-(CH2)11-CO-]Y-OH
p ∆T
H-[-NH-(CH2)11-CO-](x+y)-OH + H2O(gas)
Solid state post condensation of PA 12:
[Chain(x+y)] · [H2O] Kp,T = [Chain(x)] · [Chain(y)]
Chemical equilibrium depends on p and T
SLS provides best conditions for ‘successful’ post condensationT > 100°C; dry N2 atmosphere � drying chamber!
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∆T, t-H2Ovapor
DFvirgin = ca. 45 kD
DFaged = 70-90 kD
Solid state post condensation of PA 12: increase of molecular weight
© inspire irpd – a joint project with university of applied science St. Gallen
Why are the chain ends of PA 12 not blocked?� avoid postcondensation and aging
low melt viscosity due to open chain ends;
- increase of mechanical propertiesduring SLS-processing;
3 effects- interlinkage of SLS-layers;
solid post condensation of powder(aging)
desired
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© inspire irpd – a joint project with university of applied science St. Gallen
SLS-materials: particle properties & powder flowability
PA12 GF
© inspire irpd – a joint project with university of applied science St. Gallen
Powder distribution:
source: Vandenbroucke et al.
broad or narrow distribution?
� or even bimodal distribution…
� different philosophy from 3D-Systems and EOS
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EOS: PA 2200 3D: Duraform PA
TiO2added aspigment
© inspire irpd – a joint project with university of applied science St. Gallen
- Cryo-milling: Easy, but milled particles useless for SLS in most cases(powder density and flowability);but: DF-Flex, TPU (LehVoss) and Microfol PP are milled;
- Precipitation: solvent/non-solvent process or directly form melt intoprecipitation bath; usual process but not easy to handle(EVONIK procedure for PA 12);
- Spray drying: Evaporation through a die; very good spherical particlesbut often hollow � hardly to process; solubility, concentrations;
- Fibre cutting: Proposed by University Erlangen (D); needs an additionalprocess step: melt spinning (MS)! Viscosity of MS polymers!
- Co-extrusion: melt of the desired polymer will be extruded with a secondno-compatibel polymer; process similar to pharma-processes;
SLS-materials: preparation of powders
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© inspire irpd – a joint project with university of applied science St. Gallen
SLS-Powders – ‘state of the art’
market, current assortment, basic properties, comparison
© inspire irpd – a joint project with university of applied science St. Gallen
Market situation: The commercial major players
Major industrial USERS
WindFormDirect sales
ExcelTecDirect sales
ALM (EOS)Direct sales
ArkemaDirect sales PA12/11
Microfol (D)Direct sales PP
Rhodia/SolvayDirect sales PA 6
Evonik DSMArkema Rhodia/Solvay Japan Bayer[A]
[B] 3D SystemsEOS ASPECT China “new comers”
[C]
DAICEL(J)Direct sales
[D] LSSSystem Service
IntegraSystem Service
Others System / material Service
Service bureau USERS
Leh-VossDirect sales TPU
[A] Material[B] Machine[C] Sales[D] Service
3D SystemsDirect sales
EOS (D)Direct sales
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© inspire irpd – a joint project with university of applied science St. Gallen
74 J/m ☺32 J/mImpact strength (Izod)
47% ☺14%Elongation at break
37 MPa43 MPaTensile strength
ca. 1'500 MPaca. 1'500 MPaE-modul (MPa)
limited �goodRecyclability
small (<5 °°°°C) �large (>10 °°°°C)SLS Process window
185 - 190°°°°C175 - 180°°°°CMelting point
α-triklinγ- monoklinCrystal structure
PA11(Arkema)PA12 (Evonik)PA12 / PA11 for SLS in comparison
SLS - Standardpolymere
- suitable sintering temperatures (large window) - low melt viscosity (for medium mol weight (Mw))- Intrinsically good mechanical properties (H-bonds)
SLS-Powders – ‘state of the art’
© inspire irpd – a joint project with university of applied science St. Gallen
source: Arkema
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© inspire irpd – a joint project with university of applied science St. Gallen
source: Arkema
© inspire irpd – a joint project with university of applied science St. Gallen
Market situation: The commercial PA 12 and PA 11 materials
WindFormDirect sales
ExcelTecDirect sales
ALM (EOS)Direct sales
ArkemaDirect sales PA12/11
Evonik Arkema[A]
[B]
[C]
PA 12Orgasol
3D SystemsDirect sales
EOS (D)Direct sales
PA 12 unfilled
PA 12 GB filled
PA 12 Al filled
PA 11 Rilsan
PA 12 CF filledPA 11 GB filled
[A] neat material[B] compounder[C] available
compounds
PA 12 MF filled
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© inspire irpd – a joint project with university of applied science St. Gallen
0
1000
2000
3000
4000
5000
6000
7000
8000
9000
10000
0 10 20 30 40 50 60 70
Young's M
odulus XY [MPa]
Elonga on at break XY [%]
PA12
PA12 Glass Beads
PA12 Carbon fibers
PA12 Aluminum
PA 11
PA 11 filled
PA
12 -
CF
PA11PA12
PA12 GB/MF
PA12 Al
Properties of the commercial PA 12 and PA 11 materials
© inspire irpd – a joint project with university of applied science St. Gallen
Properties of the commercial PA 12 unfilled
1400
1500
1600
1700
1800
1900
2000
10 12 14 16 18 20 22 24 26 28 30
Young's M
odulus XY [MPa]
Elonga on at break [%]
Duraform PA
PA2200
Orgasol Invent Smooth
ALM PA 650
ALM PA 250
Innov'PA 1550
Windform FX
finepowder
coarsepowder
d50 = 58 u
d50 > 60 u
d50 = 40 u
d50 = 50 u
d50 = 55 u
d50 = 42 u
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© inspire irpd – a joint project with university of applied science St. Gallen
0
10
20
30
40
50
60
Ulti
mat
e Te
nsile
Str
engt
h [M
Pa]
Ultimate Tensile Strength XYUltimate Tensile Strength Z
Properties of the commercial materials: anisotropy
still 10-30% loss ofmechanicalproperties in Z-direction
© inspire irpd – a joint project with university of applied science St. Gallen
SLS-Powders – ‘recent developments - near future’
Polyurethane, Polypropylene, PA 6
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© inspire irpd – a joint project with university of applied science St. Gallen
SLS-Materialien: iCoPP
authorized by:iCoPP poly propylene (PP) for Selective Laser Sinteri ng!
� outstanding impact and chemical resistance� sterilisable (medical)� sealability with other PP-parts
© inspire irpd – a joint project with university of applied science St. Gallen
= poly propylene filled with glass beads
Low part density(0.85 g/cm3) andLow elongation atbreak (5,5%)
difficult to processand rough surfaces
SLS-Materialien: PP
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First TPU for SLS
from Lehmann & Voss
- tricky to process;- great detail resolution;- high flexible material;
but: not to be sold to USA for patent/licence reason s actually!
SLS-Materialien: Polyurethan
outstandingElongation at break EaB > 350%
© inspire irpd – a joint project with university of applied science St. Gallen
0
500
1000
1500
2000
2500
3000
3500
4000
4500
-50 0 50 100 150
Temperature @ RH=0 (°C)
Tensile modulus (MP
a)
Injected PA6
Sinterline
PA12
SLS-Materialien: Polyamide 6
Norm Einhe it Werte d.a.m. Cond. Allgemeine Materialkennwerte : Dichte der lasergesinterten Bauteile ISO 1183 g/cm3 1,13
Wasserabsorption bei Sättigung (23°C RH50)/Artikel ISO 62 % 3,3
Wasserabsorption bei Sättigung (23°C RH50)/Pulver
ISO 62 % 4,1
Schüttdichte ISO 60 g/cm3 0,6
Partikelgröße (D10) ISO 13320-1 µm 32
Partikelgröße (D50) ISO 13320-1 µm 66
Partikelgröße (D90) ISO 13320-1 µm 122
Mechani sche Kenn werte: Zugmodul (23°C) ISO 527 Type 1A MPa 3360 1270
Reißfestigkeit(23°C) ISO 527 Type 1A MPa 77 40
Bruchdehnung (23°C) ISO 527 Type 1A % 3,4 20
Biegemodul ISO 178 MPa 2500 980
Charpy Kerbschlagzähigkeit (23°C) ISO 179/1fU kJ/m² 2 4,7
Thermische Kennwerte:
Erster Schmelzpunkt (2°C/min) ISO 11357-3 °C 210
Wärmeformbeständigkeit (0,45 MPa) ISO 75/Af °C 191
Wärmeformbeständigkeit (1,8 MPa) ISO 75/Bf °C 77
Material for increased thermal and mechanical treatment;
Powder must be in a controlled drying condition;
Large properties difference between parts in dry/conditioned status
TECHNYL XP 1501/F Natur Polyamid (ungefüllt)
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© inspire irpd – a joint project with university of applied science St. Gallen
SLS-Materialien: Summary
• Complicated combination of desired properties of SLS powdersconstrain the easy development of new SLS materials;
• Standard materials for SLS still on PA12 base (and a little bit PA11);
• A lot of PA12-Compounds (glass beads, mineral fiber, carbon fiber,aluminum powder on the market, some variance in properties(reduction of Elongation at break);
• New materials on TPU, PP and PA 6 base are on the boarder toenter the SLS market;
• New and cheaper materials are highly necessary for marketenhancement (plastic pyramid);
Thank you!
Questions?