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Design Process
The following decision matrix compares several methods of shaping plastic bottles into prosthetic parts. We decided to test each of the methods in lab because the resulting values were all relatively close.
Shaping Theoretical Decision Matrix:
| Weight | 25 | 5 | 20 | 15 | 15 | 20 | 100% |
| Shaping Method | Cost/ Availability |
Time | Skill/ Training |
Equipment/ Tooling |
Shape Versatility |
Consistency/ Repeatability |
Total |
|---|---|---|---|---|---|---|---|
| Heat Gun/Blow Dryer | 2 | 5 | 3 | 2 | 5 | 4 | 3.2 |
| Boiling Water | 4 | 2 | 4 | 4 | 2 | 5 | 3.8 |
| Fired Oven |
3 | 2 | 3 | 3 | 2 | 3 | 2.8 |
| Propane Torch | 2 | 5 | 2 | 2 | 5 | 4 | 3 |
| Open Flame | 5 | 3 | 5 | 5 | 3 | 1 | 2.55 |
After testing, it was clear that boiling water, a propane torch and an open flame were the best shaping methods. Heating with a blow dryer did not work at all, and an open flame worked much better than expected
Shaping Test Results Matrix:
| Weight | 25 | 5 | 20 | 15 | 15 | 20 | 100% |
| Shaping Method | Cost/ Availability |
Time | Skill/ Training |
Equipment/ Tooling |
Shape Versatility |
Consistency/ Repeatability |
Total |
|---|---|---|---|---|---|---|---|
| Boiling Water | 4 | 3 | 5 | 4 | 2 | 5 | 4.05 |
| Propane Torch | 2 | 5 | 2 | 2 | 5 | 2 | 2.6 |
| Open Flame | 5 | 3 | 4 | 5 | 3 | 3 | 4 |
It was concluded that Boiling water or an open flame were both viable options.
Then arose the debate of how to effectively attach an extension that would not only deliver an added functionality, but serve as an extension of the amputee him/herself.
—New Decision Matrices to go here—
Bottle Forming Methods
Propane Torch
 |
| The torch method method did not produce uniformly spread heat. |
Open Flame
 |
| An open flame caused the bottle to shrink more uniformly and didn’t require additional equipment or propane. |
Mold Casting Methods: Current Approach used by the Center for International Rehabilitation
Mold Casting Methods: Appropriate Technology Approach
The following decision matrix shows data from testing methods of producing a negative of an arm. Plaster will be poured into the negative to form a positive that the bottle will be shaped around. Wax molding scored highest, because of the high accuracy molds, reusable wax and fast drying time. Wax is expensive, but because it is reusable and a versatile material it’s long run cost is less than clay, which is not reusable.
Molding Test Results Matrix:
| Category Weight | 20 | 10 | 30 | 10 | 10 | 80 |
| Molding Method | Cost | Set Time | Shape Accuracy/ Repeatability | Training | Equipment and Tooling | Total |
|---|---|---|---|---|---|---|
| Wax Negative | 10 | 10 | 34 | 8 | 8 | 70 |
| Clay Negative | 7 | 5 | 15 | 9 | 10 | 46 |
| Paper Mache Negative | 20 | 1 | 3 | 10 | 10 | 44 |
Wax + Plaster Casting
 |
| A wax mold was made from Aaron’s thumb. |
 |
| The mold was filled plaster of paris, creating a positive of Aaron’s thumb. |
Paper Mache
Plaster Casting in the Paper Mache Negative
Plaster Caste After Drying and a Plastic Mold
