Copyright © 2015 by Optimal Structures, LLC

LEVERAGING GEOMETRIC SHAPE

COMPLEXITY IN OPTIMAL DESIGN FOR

ADDITIVE MANUFACTURING

Yobani Martinez

Robert Taylor

Optimal Structures

2015 ATCx Conference

Houston, TX

October 8, 2015

Introduction

• Objective: Use Solid Thinking Inspire to develop

structural design concepts to leverage additive

manufacturing capabilities

• DFAM Discussion

• Case studies

• Hinge

• Upright

• UAV

• Observations

Design for Additive Manufacture

• AM enables

• Low volume (lot size of one)

• Easier design change integration (prototyping, customization)

• Piece part reductions (component combination)

• Complexity

• Geometric shape

• Hierarchical—shape complexity across multiple size scales

• Material—pointwise, layerwise

• Functional—assemblies, mechanisms

• Product performance improvement (design to match physics)

• Multi-functionality (structural and thermal and fluid and…)

Design for Additive Manufacture

• Increased geometric shape complexity can improve

structural performance (design to match physics)

• Capability to fabricate layer unrelated to layer shape

• Machining, molding operations limited by tool accessibility, mold

separation requirements

• Extreme complexity possible—mesostructures

• Lattice structures

• Load efficiency interaction

• Bending vs. Torsion

• Focus of current study

Aircraft Door Hinge Study

• Compare optimized configuration for conventional and additive manufacturing

• Requirements • Loads

• Bending

• Side loadtorsion

• Constraints • Displacement

• Stress

• Stability

• Topology Optimization • Package Space (design, nondesign)

• Objective: maximize stiffness

• Constraint: volume fraction • Conventional Manufacture (draw direction) vs Additive

Manufacture (no draw direction)

Aircraft Door Hinge Study

40% Volume Fraction 30% Volume Fraction

With draw direction—conventional manufacturing

Without hole

With hole

Aircraft Door Hinge Study

40% Volume Fraction 30% Volume Fraction

Without draw direction—additive manufacturing

Aircraft Door Hinge Study

Surface Definition using Evolve • MeshNURBS to remove data noise

• Complex surfaces—lofts, blends

New CAD Part

Conventional Manufacturing Process

• With draw direction constraint

• Total mass 6.8 lbs

Aircraft Door Hinge Study

Additive Manufacturing Process

• Without draw direction constraint

• Total mass 4.6 lbs (-33%)

Aircraft Door Hinge Study

Formula Race Car Upright Study

• Compare optimized configuration for conventional and additive manufacturing

• Requirements • Loads

• Hard turn

• x-bending

• y-torsion

• Braking

• Z-bending

• Constraints

• Displacement

• Stress

• Stability

Weight 2.68 lbs

Space 12 x 3 x 5.5 in.

Aluminum 6061

Formula Race Car Upright Study

• Compare optimized

configuration for

conventional and additive

manufacturing

• Topology Optimization

• Package Space (Design,

Nondesign)

• Objective: maximize stiffness

• Constraint: volume fraction

• Conventional Manufacture (draw

direction) vs Additive

Manufacture (no draw direction)

With draw direction—conventional manufacturing

Formula Race Car Upright Study

Volume Fraction 25% Volume Fraction 35% Volume Fraction 45%

Formula Race Car Upright Study

Without draw direction—additive manufacturing

Volume Fraction 25% Volume Fraction 30%

Min Value .9’’ Min Value .5’’ Min Value .7’’ Min Value .3’’

Formula Race Car Upright Study

Without draw direction—additive manufacturing

• 30 % volume fraction

• Max is double the min

Formula Race Car Upright Study

• Surface modeling in Evolve • Separate design,

non-design regions

• Start with polymesh cube

• Move and deform to match topology results

• Nurbify

Formula Race Car Upright Study

• Surface

modeling in

Evolve

• Import non-

design regions

• Trim, blend,

edit to get final

model

Draw

constraint

Draw

constraint

Formula Race Car Upright Study

No draw

constraint

Ongoing Work

• Size, shape

optimization

Automotive Upright Optimization

for Additive Manufacture

UAV Design Study

• Rapidly develop fuselage internal

structural configuration concept for

FDM-printed aircraft

• Thin wall structure

• Determine internal stiffening configuration

• 5 load conditions—bending about 2 axes

Wing

bending

Wing

torsion

Pitch Down

Vector

Pitch Up

Vector

Nose

landing

UAV Design Study

• Configuration

• Topology interpretation for thin

wall structure not always intuitive

• No buckling effects considered

• Sizing challenge

• Hollow members with infill

patterns

• Strength

• Stiffness

• Stability

Observations

• Inspire greatly accelerates topology optimization process

for supported modeling capabilities

• Excellent start, not final design

• Additive manufacturing enables complexity

• Geometric shape can closely match physics (load efficiency

interaction)—weight reduction

• Topology-optimized configuration requires CAD expertise—Evolve

can help

• Increases complexity of downstream shape and sizing optimization

needed to satisfy strength, stiffness, and stability criteria