Transcript Document 7822227

Manotech Associates
Initial Prototypes
April 5, 2006
Jina Kim
Forrest Liau
David Lin
Teresa Wang
Presentation Overview

Project goals (review)
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Current prototype

Next steps
Vision & Mission

Vision: Provide a method for producing an
anatomically user-matched prosthetic hand for
low-income communities

Mission: Design a prosthesis fabrication
process that a) creates a shape-matched hand
and b) uses materials that are inexpensive and
processable by the community
The Four-Step Process
Materials
Initial
Mold
 Wax
Solid
Hand
Reversible
Mold
 Plaster of  Brushable
Paris
latex rubber
Prosthetic
Hand
Silicone
rubber
Polyurethane
foam
Schedule & Prototype
March
6
13
20
27
April
3
10
17
24
May
1
8
Init. Mold
Solid Hand
Rev. Mold
Fin. Und. Prod.
Prototype
Maj. Test.
B. Plan
Poster/present.
Materials Selection
Process Optimization
TODAY
15
Prototyping Process
1.
2.
3.
4.
5.
6.
7.
8.
9.
Make plaster solid hand from wax mold
Lubricate solid hand
Brush layers of latex rubber
Lubricate reversible mold
Reverse reversible mold
Patch defects using superglue
Reinforce reversible mold by filling with water
and then dipping into wax
Reshape reversible mold as needed
Pour-in prosthesis underlayer material
Improvements Needed

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Increase space between fingers
Improve latex brushing technique
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Wait until layer is dry before applying new layer
Apply thin, even layers
Adjust orientation to compensate for gravity
Use deeper wax-heating container
Find method for holding molds with minimum
distortion
Key Challenges
Securing the solid hand and adjusting its
position continuously while applying latex
rubber
 Applying uniform layers of latex rubber
 Preventing distortions during mold
reversal

Test Observation and Setup
Load Cell = 1000lb = 5kN
Break Detection-Load level= 0.02 kN
Rate Grip Separation = 50 mm/min Gauge length ~60mm
High extension = 200 mm
Break at 171.23 nm
Problems:
-Slipping
-Bubbles
-Making the samples
Testing Result
Sample
Max Stress
(MPa)
2
3
4
0.407
0.391
0.474
Average
Mod at 50% Mod at 200%
Strain (MPa) Strain (MPa)
0.077
0.078
0.085
0.424
Young's Modulus
0.28
0.294
0.325
0.08
0.29967
1.39780884
1.450883332
1.579299844
1.476
Costs
Material
Paraffin Wax
Plaster
Rubber Latex
Foam Brush
Silicone Rubber
Source
Polygon
In 2 Art
TAP Plastics
TAP Plastics
Specialty Silicone
RTV Polyurethane
US Composites
Cost
$100.00
$3.01
$13.95
$1.00
$15.00
Amount
Cost/unit
50 lb
$20.00
4 lb
$1.13
1 qt
$1.40
1 item
$1.00
1 lb
$15.00
Total cost:
$38.52
$12.50 16 oz
$5.28
Total cost:
$66.33
Amount/unit
10 pounds
1.5 pounds
1/10 Can
1 brush
unknown
6.76 oz
Next Steps
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Tensile testing of latex rubber
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Do layers and brush techniques affect mechanical
properties?
Hardness test of prosthesis material
Method for attaching prosthesis to arm
Instruction manual
Final prototypes
Field test
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Survey general population for feedback
Questions?
Manotech Associates
[email protected]
http://web.mit.edu/3.042/team2_06/