Advanced Topics in Design for Automotive Additive Manufacturing
AutoEPCON 2019Alex JuJames McCutcheonDavid Tucker
Optional subtitle
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Agenda
1. Multi Jet Fusion Overview
2. Texture Design for Additive
– Bump Maps
– 3D Scanning
– Sculpted Textures
– Generative Methods
– Printability Considerations
3. Lattice Structures
– Structure Classification
– Cell Topology and Geometry
– Mechanical Properties
– Lattice Generation
– General Uses
AutoEPCON 2019
Multi Jet Fusion Overview
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HP Jet Fusion 3D Build Unit
Software and PluginsJob preparation and submission
Command CenterPrinter management
HP Jet Fusion 3D Printer
What is Multi Jet Fusion?
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HP Jet Fusion 3D Processing Station
• A powder-based process, where agents are deposited on a bed of powder and then fused with thermal energy
• Platform will allow the use of different agents to control voxel-level properties (such as color, conductivity, translucency)
Fusion
HP Multi Jet Fusion Manufacturing Process
Fused Fused Fused
Fused
Apply energyApply agentsMaterial Spreading
Area based melting throughput
Energy
Pattern
Heat signature
White powder temperature < melt
IR spectrum
Visible spectrum
Part temperature > melt
200
190
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160
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1 10
100
˚C
Service Parts
/ Development Production Service & Spares
Vo
lum
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Prototype Low Volume Production
Research
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Service Parts
/ Development Production Service & Spares
Vo
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Prototype Low Volume Production
High Value Applications
• Lightweight• Personalized
• Fluid Management Systems• Faster Time to Market• Energy Absorption
Research
Texture Design for Additive
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Texture Development in 3DP: Bump Maps
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Bump map applied (using planar wrapping) to a simple curved surface
2D Checker, a provided texture in
Rhinocerous
Bump Maps from Photos
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Original photograph Grayscaled image, for use as a 3D bump map
Photo-generated bump map applied to a simple surface
Seamless Bump Maps for Tiling
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Using the Offset filter & healing brush to create a seamless
texture in Photoshop
Tiled seamless image Tiled bump map applied across a simple surface
CAD-Sculpted Textures
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Textures created in Rhino, then applied to a singly-curved surface.
Use the ShowZBuffer function in Rhino to get a bump map that you can also apply to surfaces instead.
Generative Tools for Randomized Texture
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Randomly attracted barnacles to a spherical surface, flat with
the underlying surface
Randomly attracted heart-shaped molecules on a torus,
randomly oriented
Spherical molecules seeded along a chair-shaped surface
Printability Considerations
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• Tested heights/depths of 0.2mm, 0.5mm, 1mm, 2mm, and 4mm
• Logo line widths shown (outer ring): 0.4mm, 0.5mm, 0.75mm, 1mm
Printability Considerations
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Assorted test plaques, for testing the printed clarity and effectiveness of different depths and widths.
“A lattice material is defined as a spatially periodic network of structural elements.”
A. S. Phani and M. I. Hussein, Dynamics of Lattice Materials, Chichester, West Sussex: John Wiley & Sons, 2017
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Structure Classification
Lattice Structure
Uniform
• Identical unit cells are periodically distributed throughout the structure
• Are the ‘typical’ lattice structure
Random
• Cell topology and sizing are randomly distributed throughout the structure
• Examples include:
– Natural materials like cork and sponge, traditionally manufactured foams, Voronoi lattices
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Structure Classification
Lattice Structure
Pseudo-random
• Cells have the same topology, but vary in shape and size
• Used in conformal lattices to adapt to the external shape of the structure
• Conformal lattices avoid partial cells along their boundaries helping to retain integrity
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Lattice StructureFurther Classification
Homogenous
Heterogenous
Gradient
• Strut or wall thickness is kept constantthroughout the lattice
• Strut or wall thickness variesthroughout the lattice
• Strut or wall thickness varies according to a gradient function/pattern
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Unit CellCell Topology & Geometry
• Lattice materials can be comprised of open or closed cells
• Unit cells can generated from space filling polyhedra or a tessellating combination of polyhedrons
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Cubic Face Centered CubicX-Shaped Octet
Unit CellTriply Periodic Minimal Surface
• Repeat in three dimensions and are locally area minimizing
• Defined mathematically
• Most TPMS are not self intersecting
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Bending vs. Stretch Dominated
Mechanical Properties
Bending Dominated
• Responds to applied loads through the bending of unit cell beams
• Have a stress plateau in the plastic region after an initial stress peak
• Absorb a large amount of energy at lower stresses
Stretch Dominated
• Responds to applied loads through the axial stretching/compression of unit cell beams
• Exhibit higher yield stresses
• Suited to lightweight/stiff applications
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J. Souza, A. Grossmann and C. Mittelstedt, "Micromechanical analysis of the effective properties of lattice structures in additive manufacturing," Additive Manufacturing, vol. 23, pp. 53-69, 2018.
Lattice GenerationGeneralized Workflow
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Space Generation Lattice Generation Lattice Trimming/Integration
Mesh Reduction
Lattice GenerationGeneralized Workflow
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Combine the lattice with solid bodies or generate a lattice skin. Trim the lattice where needed.
Repair and reduce the resultant mesh prior to printing
Generate a closed surface/solid body (a lattice volume) that forms the boundary of the space to be filled with the lattice structure
Fill the lattice volume with the desired lattice. Many tools allow for the selection/generation of different unit cells, beam thicknesses and cell sizes
Lattice ApplicationsGeneral Uses
• Strong lightweight structures
• Auxetic structures
• Structures with low thermal expansion coefficients
• Energy absorbing structures
• ‘Tunable’ structures
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Come see more sample parts at table 18!
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