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Design by Composition for Layered Manufacturing

Design by Composition for Layered Manufacturing. Mark R. Cutkosky Stanford Center for Design Research. http://cdr.stanford.edu/interface. Outline. Layered manufacturing processes: commercial (additive) vs SDM (addition, removal, insertion) Design decomposition vs design by composition

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Design by Composition for Layered Manufacturing

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  1. Design by Composition for Layered Manufacturing Mark R. Cutkosky Stanford Center for Design Research http://cdr.stanford.edu/interface

  2. Outline • Layered manufacturing processes: commercial (additive) vs SDM (addition, removal, insertion) • Design decomposition vs design by composition • Design by composition -- implementation • Application example: biomimetic robotic mechanisms • Summary & status

  3. Layered Manufacturing: commercial example UV curable liquid Laser elevator Formed object Photolithography process schematic Sample prototype (ME310 power mirror for UT Auto)

  4. Commercial Photolithography Fused deposition Laser sintering Laminated paper Research Selective laser sintering (UT Austin) 3D printing (MIT) Shape deposition manufacturing (CMU/Stanford) Layered manufacturing processes Engineering materials (metals, ceramics, strong polymers) Graded materials Embedded components Not quite direct from CAD model... “Look and feel” prototype Complex 3D shapes direct from CAD model

  5. Shape Deposition Manufacturing (CMU/SU) Embedded Component Part Support Deposit (part) Shape Shape Deposit (support) Embed

  6. SDM#1: Injection mold tooling (SU RPL)

  7. SDM #2: Frogman (CMU) • Example of polymer component with embedded electronics

  8. Approaches to design with layered shape manufacturing Usually people think of taking a finished CAD model and submitting it for decomposition and manufacture Example: the slider-crank mechanism, an “integrated assembly” built by SDM

  9. Decomposition into ‘compacts” and layers • Several levels of decomposition are required Complete Part Compacts Layers Tool Path

  10. Definitions: Compact[Merz et al 94] • 3-D volume with no overhanging features • Rays in growth direction enter only once • Compacts correspond to SDM cycles z2 z1 Build Axis (a) no good (b) OK (c) OK

  11. Layers produced by automatic decomposer for slider crank mechanism Gray = steel, brown = copper support material

  12. Layered shape deposition - potential manufacturing problems • finite thickness of support material • poor finish on unmachined surfaces • warping and internal stresses • decomposition depends on geometry,not on intended function

  13. Design by Composition(M. Binnard) Users build designs by combining primitives with Boolean operations • Primitives have high-level manufacturing plans • Embed components and shapes as needed Primitives merged by designer Manufacturing plans merged by algorithm

  14. Primitive = Compact Set + Precedence Graph Primitive Compact set Compact precedence graph • Set of valid compacts • No intersections • Fills the primitive’s projected volume • Acyclic directed graph • Link for every non-vertical adjacency

  15. A B Merging Algorithm Example + = A B C=A È B intersection compacts non-intersecting compacts

  16. a3 Ç = Æ b1 Ç = Ç = a2 b1 a2b1 A B C Ç = a1 b1 a1 b1 Algorithm: intersection compacts • Find every compact intersection • Material type depends on operation, f(a,b) a3 a2 b1 a1 b2 Truth tables for result material (etc. )

  17. CPG Simplification algorithm • Combine compacts of the same material • Multiple solutions • Optimum depends on functional and manufacturing considerations 7 7 6 5 6 4 5 2 3 3+4 2 1 1

  18. Algorithm closure and efficiency demonstrated for multi-material parts and embedded components (Binnard 99) • Minimal geometric Boolean operations (incremental merging and simplification) • Worst-case scaling • Compact set merging: O(n2) • CPG link generation: O(n4) • Simplification: O(n3 ) (In practice, 10-20 merged compacts for moderately complex designs)

  19. design by composition toolbar Implementation • AutoCAD R14 plug-in (compacts and projected volumes on hidden layers) • ACIS toolpath planner (extruded shapes, 3D surfaces underway)

  20. a) (top view) b) (side view) d d d(a1,a2) d(a1,a2) l 2l Dd Minimum gap/rib thickness Generalized 3D gap/rib e) (side view) 2l l d(m1,m2,m3) d(m1,m2,m3,a1,a2) Wc/l >= 2 m1 m2 m3 m1 m2 m3 Minimum feature thickness Toward a mechanical MOSIS? SFF/SDM VLSI Boxes, Circles, Polygons and Wires Decomposed Features SFF/SDM Design Rules Mead-Conway Design Rules

  21. Future Work: Integration with Decomposition Composition CAD Traditional CAD feedback solid model new primitive Analysis feedback Orientation Bold arrows are transmission of compact graphs Compact Splitting Analysis Path Planning CNC code Machine Tools

  22. Shaft coupling Shaft Motor Leg links Application: Small robots with embedded sensors and actuators Building small robot legs with pre-fabricated components is difficult… Is there a better way?

  23. Robot leg example(http://cdr.stanford.edu/biomimetics) Steel leaf spring Designer composes the design from library of primitives, including embedded components Piston Part Primitive Outlet for valve Valve Primitive Circuit Primitive Inlet port primitive

  24. Robot Leg design (cont’d.) Steel leaf-spring Internal components are modeled in the 3D CAD environment. Piston Sensor and circuit Spacer Valves Components are prepared with spacers, etc. to assure accurate placement.

  25. Robot Leg: compacts The output of the software is a sequence of 3D shapes and toolpaths. Embedded components Part Support

  26. Robot leg: manufacturing Manufacturing takes place in the Stanford Rapid Prototyping Lab Part material is Urethane. The support is red and blue wax. Cavities inside valves were first filled with soap. Deposition

  27. Robot Leg: embedded parts Steel leaf-spring Piston Sensor and circuit Valves A snapshot just after valves and pistons were inserted.

  28. Robot Leg: completed Finished parts ready for testing

  29. Summary & status • New technology provides novel design opportunities • Designers need access to develop an experience base • Making these processes widely used requires: • Ease of use • Flexibility (e.g, decompose geometry or build from primitives) • Quick feedback • What are we doing? • Creating a design/manufacturing interface for layered processes • Creating design libraries and design rules

  30. Acknowledgements Thanks to M. Binnard, S. Rajagopalan, J. Cham, B. Pruitt and Y. Sun for their help in generating the results described in this presentation and to the Stanford Rapid Prototyping Lab for their help in building the parts. This work has been supported by the National Science Foundation (MIP-9617994) and by the Office of Naval Research (N00014-98-1-0669)

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