selective laser melting opportunities and limitations · selective laser melting / laser powder bed...

A.B. SpieringsDr.-Ing. ETHZ, Head R&D SLM

Inspire AG – innovation centre for additive manufacturing Switzerland

16th int. Bhurban Conference on Applied Sciences and Technology

Selective Laser Melting –

Opportunities and limitations

8. – 12. January 2019

Islamabad, Pakistan

Who’s inspire?

Introduction to additive manufacturing

Opportunities with Selective Laser Melting (SLM)

Limitations of & R&D needs for SLM

Trends & Conclusions

Agenda

Who’s inspire?

… the national (Swiss) non-profit R&D centre for advanced manufacturing technologies

Who’s inspire?

Inspire

is a competence centre for the swiss machine manufacturing industry, with close relations to ETH in

Zurich.

is a common initiative of Swissmem, the Swiss Federal Institute of Technology ETH, and the State

Secretariat for Education, Research and Innovation (SERI).

Who’s inspire?

… the national (Swiss) non-profit R&D centre for advanced manufacturing technologies

Who’s inspire? Who’s inspire?

facts & figures

Non-profit technology transfer institute

Focus on production technology

> 80 Employees, 20 working on AM-topics

Inspire-icams (St.Gallen)

12 people

> 20 running R&D projects

Continuously Bachelor / Master projects (ETH, Europe)

Inspire AM lab in St.Gallen

Industrial AM-

applications

Research goals Who’s inspire?

Applications

AM-Machines

AM-Processes

AM-Materials

Industry

requirements

Sources: Intenet

Materials

• Powder requirements

• Materials for AM • Alloys for additive

manufacturing (e.g. Al)

• Hybrid materials

• Material characterization• Material integrity

(cracks, pores, …)

• Microstructure

• Static / dynamic mechanical properties

• …

AM-Processes

• Processing window for various materials

• SLM- / SLS- Process Simulation• Internal stresses

• Process effects

• Monitoring solutions

• Process productivity & performance

• Process chain view

Machine

• Future machine concepts

• Optimization of machine components

• Interconnectivity, machine lines

• Quality management systems

Applications

Space / Aerospace / Industry

Lightweight structures

Structurally optimised parts

Tooling, mould & die

Pre-serial AM-Development

Large structures & coating

Embedded functions

Standardisation (ASTM-ISO, VDI)

Research topics Who’s inspire?

International network Who’s inspire?

Introduction to additive manufacturing

Definition

Principle

Additive Introduction to additive manufacturing

“Additive manufacturing (AM), n – processes of joining materials to make objects from 3D

model data, usually layer upon layer, as opposed to subtractive manufacturing fabrication

methodologies.”

Energy

Melt-pool

CAD model Slice-process Layer information Build process

Selective Laser Melting / Laser Powder Bed Fusion

Metal additive manufacturing Introduction to additive manufacturing

Electron Beam Melting

Direct Metal Deposition

Laser Powder Bed Fusion - LPBF

Electron Beam Powder Bed Fusioon - EBM

Powder feed additive manufacturing - DMD

Introduction to additive manufacturingAdvantages & disadvantages

[inspire, 1 - 8]

Advantages

− No undercuts – “all” geometries are possible

− New optimized design are possible

- bionic / lightweight

− Production of lot-size ONE

− “Customised” design

− Different geometries in the

same build process

− Complex structure already assembled

− Functional integration

Disadvantages

− Limited number & process-specific materials, esp. for plastic materials

− Finishing required (support structures, surface quality)

− Lot-sizes: from 1 to 100 / 1000 - not for big series!

Introduction to additive manufacturingAdvantages & disadvantages

Redesign for Additive

Manufacturing

“Complexity for free” [Source: A.Spierings]

Industrial opportunities

Tooling

– Conformal cooling / heating

channels

– Internal channels

OpportunitiesFields of application of LPBF

Source : Concept Laser

Source : inspire, Hufenus et al. 2012

Source : inspire Source : inspire

Functional integration

– Assembled parts

– Integration of added value,

and new functions

– Integration of sensors into

metallic parts

Source : inspireSource : inspire

Lubrication supply

CFD-optimized channels

Lightweight structure &

Gas ionization delivery & suction

Machinery

– Turbine industry

– Blades / vanes

– Injection nozzles

– …

– Machine industry

– …

Source : Morris Technologgy / GESource : www.shining3dscanner.com)

Source : inspire & Burckhardt Compression

Jet engine

combustor

Source: EOS

Injection

nozzle

Source : inspire

– Lattice lightweight structures

Weight savings up to 60%

– Topology optimization

Source : inspire Source : RUAG Space

Source : inspire Source : inspireSource : inspire

– Lattice lightweight structures

– Outer shell load bearing structure

– Innter lattice structure Stabilization of the outer shel

Source: inspire

Core-shell strucutreSingle lattice structure

“3-dimensional double T-beam”

Lightweight structures – Bionic counterpart

Bamboo core shell strucutre Bone core shell strucutre

Source: Internet

Mechanical engineering

Space & Aerospace

– Structural parts

– Lightweight components

– …

Insert structures for space composite panels

Source: inspireSource: inspire

Space & Aerospace

– Structural parts

– Lightweight components

– Brackets

– …

Source: RUAG Space

Source: GE-Additive

Space & Aerospace: Examples

3D Printing in space:

The «MELT project»(Manufacturing of Experimental

Layer Technology)

FDM-printer on the ISS

https://3druck.com

Airbus To 3-D-Print Airframe Structures

The EBAM 110 e-beam AMsystem from Sciaky,

to print large m-sized Ti aircraft structural parts.NASA's additive test program included

a hydrogen-oxygen rocket injector

What began as a unit with over 150 individual

pieces requiring months to manufacture was

transformed by AM into a two-part, 3D printed

unit built in 10 days.

Space & Aerospace

– A recent study found that aircraft weight could be reduced by 7% just by replacing conventional

means of manufacturing with additive manufacturing.

Limitations & R&D needs

Limitations

Huge expectations

… only realistic if industrial requirements

are met:

- Part quality

- Process stability

Need for quality & reliability !

Part- costs

Production technology

Prototyping

Niche technology

Low-tec technology

Fields of application of LPBF

From powder to the final part

The SLM-process chain Limitations

Spierings (2018)

LimitationsPart quality

[Spierings 2018]

Question: What is “AM-part quality” ?

Which parameter affects quality?

What are the (really)

relevant parameters?

What are their specific

level of influence ?

How do we measure

them (correctely)?

Metrology

How is their variation

reduced?

LimitationsPart quality

[Spierings 2018]

Material Integrity– Pores, Irregulare defects, cracks, …

– Mechanical properties– Anisotropy in static / dynamic mech. properties

– Fracture toughness, …

Mikrostructure– Grain size distribution

– Solidification principles

– …

Surface properties– Dependent on powder properties

– Dependent on part orientation

– Dependent on process parametes

– …

Accuracy– Dependent on powder, process window etc.

– 0.1 bis 0.2mm

AlSi12: Side surface «smooth»

AlSi12: Side surface «rough»

EBSD of a AlSi12 alloy, inspire-icams

Typic pore distribution in AM-parts . Source:

inpsire

LimitationsInfluencing parameters

Estimation:

Up to 150 influencing

parameters exist

along the process

chain. (Rehme et al.)

Expected

≥ 50 parameters

directly affect the

quality of the process,

and the final part.

Example powder: Varying powder properties

Parameters Particle size distribution Particle shape

Powder flowability

Essential influence on the resulting process- & material properties

Spierings, A.B., et.al, Powder flowability characterisation methodology for powder-bed-based metal

additive manufacturing. 2015, Progress in Additive Manufacturing: p. 1-12.

Influencing parameters: Challenges Limitations

«coarse» powder «fine» powder

Good powder layer quality Bad layer quality

LimitationsInfluencing parameters: Challenges

Example powder: Varying powder properties

Variations in powder properties affect

the process quality & efficiency.

Speed 1 Speed 2 > 1 Speed 3 > 2

[Spierings 2018]

Process characteristics

Influencing parameters

Very smallmelt-pool

Very shortlaser

interactiontime

Very high temperature

gradients

Very high cooling

Ion J (2005)

Melt pool sizes

Characteristic size 1/10 mm

Dependent on

laser parameters

physical material parameters

(e.g. conductivity)

Marangoni convection

Very smallmelt-pool

Very shortlaser

interactiontime

gradients

Very high cooling

Laser interaction time @ high intensity

Characteristic interaction time 1/100 - 1/1000 s(high scan speeds)

Very smallmelt-pool

Very shortlaser

interactiontime

gradients

Very high cooling

Cooling rates and gradients

Very high cooling rates𝑑𝑇

𝑑𝑡= 𝐺 ⋅ 𝑅 up to 103 to 105 Ks-1

Solidification front stabilityΔ𝑇0

𝐷𝑙=

𝑅instable if

Δ𝑇0

𝐷𝑙>

Very smallmelt-pool

Very shortlaser

interactiontime

gradients

Very high cooling

G… temperature gradient in the melt-pool

R… solidification front growth rate

T0… equilibrium solidification temperature range

Result:

Non-equilibrium solidification

Impact on precipitation

behavior,phases etc.

Fine microstructures Long elongated grains parallel to the build

direction (BD), …

Often > 100 m, hence much

longer than a layer thickness

with a comparably small

diameter

Typical range

5m to 20m

Anisotropic mechanical behaviour

(Hall Petch)

Examples

Limitations

Example alloy composition / non-equilibrium solidification (IN738LC)

Traditional alloy compositions do not need to fit to the AM-processing conditions.

Defects (cracks etc) can be the result!

[Cloots et al., inspire] Typical defects in AM-materials Grain boundary cracking & crack surface analysis

[Cloots et al., inspire]

Example alloy composition / non-equilibrium solidification (IN738LC)

For AM-processes, the alloy compositions may require narrower tolerances.

APT analysis of a grain boundaryNon-equilibrium solidification simulation

(Scheil)

Example alloy composition: Aluminium

For AM-processes, alloy design is required to overcome typical problems:

Increased defect formation (Cracks / porosity)

Columnar grains & preferential grain orientation Anisotropic mechanical properties

AlSi10Mg microstructure (Thijs et al. 2013)Young’s modulus in dependence of sample orientation during SLM

of AlSi10Mg alloy (Hitzler 2017)

[Spierings et al. 2018]

Example alloy composition: 5xxx Aluminium alloy design

Alloy design for AM can overcome some of these bottle necks

Example: Al-Mg-Sc-Zr alloy

almost no anisotropic mechanical properties

Grain size stabilization

Advanced microstructure control in Al-Mg-Sc-Zr alloysAnisotropy-free mechanical properties

LimitationsQuality management for AM-processes

[Spierings 2018]

Quality considerations along the AM-process chain

Trends & conclusions in metal AM

Trends

Productionmachines

•Not prototpying

•New machineconcepts /application specific

•Processchainautomation

• Increase in productivity

Processfeedbackcontrol

• In-line process-and part qualitycontrol

•Neuronal networks

Quality managementSystems

•Process quality

•Part quality

Materials

•Alloys for AM

•New materials

Standardization

•Processes

•Materials

•Quality measures

•…

Development needs

DMG-Mori: Lasertec 65

Trends & conclusionsTrends in metal AM

5 m long Ti wing beams

for the C919 plane

Laser Powder Bed Fusion

Binder Jetting

Powder feed

Wire feed

Electron Beam Melting

Part sizes Lot sizes

mm to dm

cm to dm

dm to m

Low to medium

Medium to high

medium

Trends in metal AM Trends & conclusions

(Metal) additive manufacturing

– …has achieved important industrial perspectives for improved part performances

– Lightweight

– Structural optimization

– Functional integration

– …is still facing significant R&D needs in terms of

– Missing quality management systems accross the process chain

– Improved process (feedback) control

– Alloy design for AM

– Standardization

– …LPBF will face competition with alternative AM-technologies

– Binder Jetting (HP)

– Powder / wire feed systems

Conclusions Trends & conclusions

A.B. SpieringsDr.-Ing. ETH ZurichHead R&D SLM

Lerchenfeldstrasse 3

9014 St.Gallen

spierings@inspire.ethz.ch+41 71 274 73 19

www.inspire.ethz.ch

Springer Journal «Progress in Additive Manufacturing»ISSN: 2363-9512 (print version)

ISSN: 2363-9520

• Reduced peer-review time for short

communications.

• Double-blinded peer-review system for all

submitted papers.

• Interdisciplinary topics ranging from data

processing to simulation, new and hybrid

process, to materials and microstructural

analysis.

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