commercial sls powders - eth z · commercial sls powders - state of the art and recent developments...

1

© 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


� 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)

2


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).


research institute with production facility � service bureau!Introduction: irpd

customer feedback

fit for Industry

3


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


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

4


SLS-Powders – combination of propertiesparticle distribution, thermal behavior, rheology, aging

Why is it so complicate to make a new SLS powder?

or


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

5


SLS-materials:thermal properties

Curling


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)

6


Ts

Lateral growth and curling trade off with part

bed temperature

Lateral growth

Curling

∆∆∆∆T Part bed:

5°°°°C !

Characterization Methods: DSC


SLS-materials:rheological properties

7


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!


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

8


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


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!

9


∆T, t-H2Ovapor

DFvirgin = ca. 45 kD

DFaged = 70-90 kD

Solid state post condensation of PA 12: increase of molecular weight


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

10


SLS-materials: particle properties & powder flowability

PA12 GF


Powder distribution:

source: Vandenbroucke et al.

broad or narrow distribution?

� or even bimodal distribution…

� different philosophy from 3D-Systems and EOS

11


EOS: PA 2200 3D: Duraform PA

TiO2added aspigment


- 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

12


SLS-Powders – ‘state of the art’

market, current assortment, basic properties, comparison


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

13


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’


source: Arkema

14


source: Arkema


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

15


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


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

16


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


SLS-Powders – ‘recent developments - near future’

Polyurethane, Polypropylene, PA 6

17


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


= 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

18


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%


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



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)

19


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?

commercial sls powders - eth z · commercial sls powders - state of the art and recent developments...

Documents