Shape Deposition Manufacturing for 7:30am

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Shape Deposition Manufacturingfor 730am

• May 2003
• Motohide Hatanaka
• Center for Design Research
• Stanford University, USA

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http//www.lib.utexas.edu/maps/world.html http//w
ww.geneve-tourisme.ch/ http//www.jnto.go.jp/eng/R
TG/RI/index.html
http//www.u-tokyo.ac.jp/ http//www.stanford.edu/
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The Biomimetic Robotics lab
We value experience. Even being cockroaches.
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Grammatical introduction
Shape Deposition Manufacturing
(Deposit-and-Shape Manufacturing)
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Repetitive machining and deposition
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Animation!
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Cyclic deposition and shaping
Prepare mold block
Machine mold
(place component to embed)
Deposit material
Shape mold/part
Extract part
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SDM capabilities
Multi-material molding
Component embedding
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Part number reduction
Left Kinematic prototype of stroke extension
linkage with 31 parts Center Single component
SDM linkage with thick flexures Right SDM
linkage with thin fabric-reinforced flexures
(2001)
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SDM merits
robustness
No fasteners
easy to automate
Arbitrary shapes
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What weve embedded

• Servo motors
• pneumatic pistons
• sensors
• Printed circuit board
• flexible printed circuit (Cupolyimide)
• electrical wiring
• electrical connectors
• springs
• fabric (cotton, polyester, etc)
• strings (cotton, polyester, etc)

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Embedded sensor example (continued)
A batch of four parts during the final machining
step. Part material is urethane (yellow).
Sacrificial support material is wax (red),
filling cavities and encasing the circuit leads
to protect them.
Completed pressure sensor unit ready for
connection to a pneumatic actuator.
Fabrication instructions archived at
http//cdr.stanford.edu/dml/biomimetics/documents
.html
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Example embedded actuators
Antagonist electric motors with cable
tendons. Photo taken after machining, half way
through build sequence
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Embedded actuator example contd
Shaping structures are machined a pallet on a
CNC mill
Deposition part and support materials are cast
in place, after each machining stage
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Undercut with sacrificial material. Top shaping
by machining.
Primitive
Compact set
Compact precedence graph
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Limitations/requirements

• Mold size maximum part size (approximately
  300 x 300 x 150 mm)
• Mostly serial process (Plastic curing time
  24 hours)
• Materials Small shrinkage (e.g. polyurethane,
  epoxy, silicone)

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Materials we use

• Polyurethane (soft, medium, hard)
• Silicone
• Epoxy
• Wax (temporary sacrificial material)
• Water soluble wax (also sacrificial)
• We will be trying
• Conductive polymer/elastomer

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Design guidelines

• Minimize number of material castings
• Ensure machining tool accessibility
• Consider material compatibility, machinability,
  and casting order
• Soft materials, usually, can only be machined
  with high speed fly cutters.
• Consider using larger tools for faster machining.
  (Doubling tool diameter can speed up material
  removal by x8!)

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Problems experienced

• Bubble formation in polymer (esp. PU)
• humidity in atmosphere
• insufficient degassing
• material combination (casting soft polyurethane
  on hard polyurethane ?)
• chemical reaction with adhesives
• Difficult to machine soft materials
• Bonding weakness (same as ?)
• Delamination in composite structures
• High curing temperature

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Remember this cycle!
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More animation?
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And more?
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Still more?
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OK, this is the last animation.
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(No Transcript)
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Design and fabrication of compact mechatronic
systems by shape deposition manufacturing
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Biology is a target for complex integrated
structures manufacturing
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Cross-boundary embedding
Application electrical wiring, structural
reinforcement, fiber optics, plumbing
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Cross-boundary embedding difficulties
1. Secure fixturing 2. Insert obstruction/damaging
in selective processes 3. Stress
concentration
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Types of fabrication processes
Bulk deposition (e.g. molding/casting) Bulk
removal (e.g. dissolving)
Selective deposition (e.g. fused
deposition) Selective removal (e.g. machining)
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Selective deposition of sacrificial material
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Selective deposition of part material
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Four main methods of cross-boundary embedding
I. Selective deposition of part
material II. Selective removal of part
material III. Selective deposition of
sacrificial material IV. Selective removal of
sacrificial material
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Psuedo-boundary formation
Bulk deposit material A and machine Place
insert Bulk deposit material B
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Pre-encapsulation
Place pre-encapsulated insert in mold Bulk
deposit material A Selective remove material
A Bulk deposit material B
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Alternative methods
V. Pseudo boundary formation VI.
Pre-encapsulation
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Available process options
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Reasons to choose an alternative method
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Prioritization for cross-boundary embedding
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Manufacturability consideration
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Summary of work up-to-date
Motivation Build complex integrated mechanisms
as in biology
Key technology Cross-boundary embedding
Success in preliminary attempts
Process characteristics identification
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Design guidelines
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Possibilities to be explored

• Controlled material deposition as in many rapid
  prototyping technologies (e.g. ink jet)
• Tools to facilitate manual selective processes
  (e.g. fine wax deposition gun)
• Material-property dependent selective deposition
  and removal (e.g. crystallization, chemical
  etching)

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Other challenges for realizing compact integrated
structures

• Three-dimensional electrical wiring for power and
  signal transfer.
• Three-dimensional plumbing for hydraulic,
  pneumatic, and fuel distribution.
• Development of optimal function-integrated
  structures, e.g. fuel-cell-integrated skeleton.