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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

Design by Composition for Layered Manufacturing

Mark R. Cutkosky

Stanford Center for Design Research

http://cdr.stanford.edu/interface

outline
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
layered manufacturing commercial example
Layered Manufacturing: commercial example

UV curable

liquid

Laser

elevator

Formed

object

Photolithography process

schematic

Sample prototype (ME310 power mirror for UT Auto)

layered manufacturing processes
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

shape deposition manufacturing cmu su
Shape Deposition Manufacturing (CMU/SU)

Embedded Component

Part

Support

Deposit (part)

Shape

Shape

Deposit (support)

Embed

sdm 2 frogman cmu
SDM #2: Frogman (CMU)
  • Example of polymer component with embedded electronics
slide8
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

decomposition into compacts and layers
Decomposition into ‘compacts” and layers
  • Several levels of decomposition are required

Complete

Part

Compacts

Layers

Tool Path

definitions compact merz et al 94
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

layers produced by automatic decomposer for slider crank mechanism
Layers produced by automatic decomposer for slider crank mechanism

Gray = steel, brown = copper support material

layered shape deposition potential manufacturing problems
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
design by composition m binnard
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

primitive compact set precedence graph
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
merging algorithm example
A

B

Merging Algorithm Example

+

=

A

B

C=A È B

intersection compacts

non-intersecting compacts

algorithm intersection compacts
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. )

cpg simplification algorithm
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

slide18
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)

implementation
design by

composition

toolbar

Implementation
  • AutoCAD R14 plug-in (compacts and projected volumes on hidden layers)
  • ACIS toolpath planner (extruded shapes, 3D surfaces underway)
toward a mechanical mosis
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

future work integration with decomposition
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

application small robots with embedded sensors and actuators
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?

robot leg example http cdr stanford edu biomimetics
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

slide24
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.

slide25
Robot Leg: compacts

The output of the software is a sequence of 3D shapes and toolpaths.

Embedded components

Part

Support

slide26
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

robot leg embedded parts
Robot Leg: embedded parts

Steel leaf-spring

Piston

Sensor and circuit

Valves

A snapshot just after valves and pistons were inserted.

slide28
Robot Leg: completed

Finished parts ready for testing

slide29
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
acknowledgements
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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