topology optimization for additive manufacturing world conference... · 29-3-2016 1 structural...

29-3-2016

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Structural Optimization & MechanicsDelft University of Technology

Topology Optimization for Additive Manufacturing

Matthijs Langelaar

m.langelaar@tudelft.nl

State of the Art and Challenges

Additive World Conference 2016

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Additive manufacturing: focus on design

AM enables the fabricationof “almost any” design.

So.. what design to make?

Topology optimization

Additive manufacturing

Concept geometry

Detailed design

Final component

Post-machining

From functionality to product

Desired functionality

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Aligned advantages

Topology Optimization

• Design freedom: part performance not limited by imagination of designer

• Time to market:fast, nearly automated design process

• Customization:tailored designs for specific requirements

Additive Manufacturing

• Design freedom: relatively few shape restrictions, ‘complexity for free’

• Time to market:no tooling needed, on-demand production

• Customization:produce many different part at once

SLM limitation: critical overhang angle

Clijsters et al, 2012

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Existing solutions to overhang problem

1. Adjust part orientation

2. Adjust part itself

3. Add support structures

Topology optimization

Additive manufacturing

Concept geometry

Detailed design

Final component

Post-machining

Design for manufacturing

Desired functionality

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Structural Optimization & MechanicsDelft University of Technology

Topology Optimization for Additive Manufacturing

Matthijs Langelaar

m.langelaar@tudelft.nl

Additive World Conference 2016

• Aim: include overhang restrictions in topology optimization

• Benefits:

• No need for support structures: less material usage

• Less pre-processing for AM

• Less post-machining: faster production, lower costs

Outline

• Motivation

• Brief introduction to topology optimization

• Print-ready topology optimization

• Approach

• Simplified AM process model

• Examples

• Next steps

• Concluding remarks

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Topology optimization: generating the best material distribution

bracket

What shape to use?

design domaintopology optimization resultpost-processed final design

Where to place material?

Topology optimization process

1. Define problem:

2. Discretize and parameterize material distribution

3. Optimize material distribution forbest performance

- Objective, constraints- Domain, boundary conditions- Loadcases

4. Evaluate / fine-tune result(postprocessing, shape optimization)

Load

Maximize stiffnessUse only 50% material

i

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Topology optimization loop

Values of the density variables

Componentanalysis

(FEA)Values of theobjective and constraints

New

Optimizationalgorithm

Gradient information(design sensitivity)

New

New

Example: compliant mechanism design

• Maximize desired motion

• Sufficient stiffness in other directions

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Outline

• Motivation

• Brief introduction to topology optimization

• Print-ready topology optimization

• Approach

• Simplified AM process model

• Examples

• Next steps

• Concluding remarks

Current practice

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Print-ready topology optimization

Builddirection

Comparison

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Previous approaches

• Automatic post-processing

• Suppressing overhang using filtering techniques

Leary et al., 2014

Gaynor and Guest, 2014

Previous attempts @ TU Delft

• Filter-based approach

• Boundary angle constraints

• Boundary angle constraints with level sets

Serphos, 2014

Driessen, 2015

Van de Ven, 2015

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Topology optimization for print-ready designs

Values of the density variables

Componentanalysis

(FEA)Values of theobjective and constraints

Optimizationalgorithm

Gradient information(design sensitivity)

printed design

Topology optimization for print-ready designs

Componentanalysis

(FEA)Values of theobjective and constraints

Optimizationalgorithm

Gradient information(design sensitivity)

blueprint design

Printingprocess

simulation

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AM process model

F

Builddirection

45 critical overhang angle assumed

AM process model formulation

0.8

0.30.5 0.0

0.5

support 1 2 3max , ,

print blueprint supportmin ,

Builddirection

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AM process model formulation

support 1 2 3max , ,

print blueprint supportmin ,

Langelaar, 2016, in review

printed design

Topology optimization for print-ready designs

Componentanalysis

(FEA)Values of theobjective and constraints

Optimizationalgorithm

Gradient information(design sensitivity)

blueprint design

Printingprocess

simulation

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AM process model: implementation

• min/max operations are not differentiable: replace by smooth approximations

• Layer-by-layer processing:printing simulation in build direction,sensitivity analysis in reverse direction

• Computational cost: very minor (1%)

Outline

• Motivation

• Brief introduction to topology optimization

• Print-ready topology optimization

• Approach

• Simplified AM process model

• Examples

• Next steps

• Concluding remarks

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Examples

• Process simulation test

• 2D validation

• 3D validation

Process simulation test

Blueprint design

Printed design (ideal)

Printed design(smoothed process model)

Builddirection

• Solid parts fully correct

• Light gray parts gradually fade out

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2D validation: test problem

• Maximize stiffness

• 50% material

N

S

W E

2D validation: printability of reference design

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Topology optimization for AM

Printable, self-supporting designsachieving near-ideal performance

94%94% 100.0%100.0% 99%99%90%90%

100%100%

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Higher resolution test

100%100%

93%93% 94%94% 100%100% 98%98%

3D validation

• Maximize stiffness

• 30% material

• 6 orientations

F

Langelaar, 2016, in review

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Reference design

Printability of reference design

Builddirection

As printed

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Topology optimization for AM

Builddirection

100% printable

Different part orientation

F

Builddirection

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Design with ‘support structures’

Different orientations, different designs

100%100%

100%100%

99%99%93%93%

93%93%

101%101%

102%102%

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Beyond beams

Reference PrintablePrintable Builddirection

Outline

• Motivation

• Brief introduction to topology optimization

• Print-ready topology optimization

• Approach

• Simplified AM process model

• Examples

• Next steps

• Concluding remarks

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Limitations

Current approach fast and effective, but:

• Based on structured, regular mesh

• Fixed 45 critical angle

• Limited to 6 main build directions

• Only fully supported designs, no control over

performance vs. support structure cost

• No consideration of stress, distortion, overheating

Current developments

• Formulation that • works on arbitrary meshes• for any critical angle• and any build direction

Emiel van de Ven

• Formulation that allows tradeoff solutions between support structure cost and part performance

• Development of more advanced thermomechanical AM process models

Marius Knol, Can Ayas

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Concluding remarks

• Topology optimization can provide the designs needed to fully benefit from AM freedom

• Topology optimization for AM generates fully printable optimized designs: this eliminates the need and costs of part redesign, supports, postprocessing

• Including AM restrictions can maintain high design performance

• Methods hopefully soon adopted by commercial software companies

Structural Optimization & MechanicsDelft University of Technology

Topology Optimization for Additive Manufacturing

Matthijs Langelaar

m.langelaar@tudelft.nl

Additive World Conference 2016