This document summarizes several case studies that leverage additive manufacturing capabilities by developing structural designs with increased geometric complexity through topology optimization. Case studies included an aircraft door hinge, formula race car upright, and UAV fuselage internal structure. Topology optimization was used to develop designs optimized for additive manufacturing without constraints, allowing greater geometric complexity compared to conventional manufacturing. Post-processing was required to define surfaces and sizes for final designs. Observations noted additive manufacturing enables designs matching physics for weight reduction, and increased downstream optimization is needed to satisfy all criteria.

1. 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

2. Introduction
• Objective: Use Solid Thinking Inspire to develop
structural design concepts to leverage additive
manufacturing capabilities
• DFAM Discussion
• Case studies
• Hinge
• Upright
• UAV
• Observations

3. 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…)

4. 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

5. Aircraft Door Hinge Study
• Compare optimized configuration for conventional
and additive manufacturing
• Requirements
• Loads
• Bending
• Side loadtorsion
• 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)

6. Aircraft Door Hinge Study
40% Volume Fraction 30% Volume Fraction
With draw direction—conventional manufacturing
Without hole
With hole

7. Aircraft Door Hinge Study
40% Volume Fraction 30% Volume Fraction
Without draw direction—additive manufacturing

8. Aircraft Door Hinge Study
Surface Definition using Evolve
• MeshNURBS to remove data noise
• Complex surfaces—lofts, blends

9. New CAD Part
Conventional Manufacturing Process
• With draw direction constraint
• Total mass 6.8 lbs
Aircraft Door Hinge Study

10. Additive Manufacturing Process
• Without draw direction constraint
• Total mass 4.6 lbs (-33%)
Aircraft Door Hinge Study

11. 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

12. 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)

13. With draw direction—conventional manufacturing
Formula Race Car Upright Study
Volume Fraction 25% Volume Fraction 35% Volume Fraction 45%

14. Formula Race Car Upright Study
Without draw direction—additive manufacturing
Volume Fraction 25% Volume Fraction 30%

15. 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

16. 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

17. Formula Race Car Upright Study
• Surface
modeling in
Evolve
• Import non-
design regions
• Trim, blend,
edit to get final
model

18. Draw
constraint
Draw
constraint
Formula Race Car Upright Study
No draw
constraint
Ongoing Work
• Size, shape
optimization
Automotive Upright Optimization
for Additive Manufacture

19. 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

20. 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

21. 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