Prosthetic Arm Force Reducer Team 1 – Halliday's ... - Ohio University

manufacturing costs are $525.00. This is a decrease from the alpha prototype of $1125, and puts
the overall cost of the system to $575.86. This is an alpha to beta savings of $1252.31. The main
reasons for this price drop are the inefficient use of alpha materials and the errors in the
manufacturing. This price is in the 10- 15% range of the total prosthetic arm cost of $6000.
Table 7.3.4 - Manufacturing Costs for Beta Prototype
Operation Operation Operation
1 2 3 Operation 4
Cut Cut
square grooves in
tracks to pulley axle
desired to allow
Cut pipe length travel in
tubing to and drill the tracks.
1" sections bolt Insert into
and turn holes. pulley and
down on Mill lock into
lathe. opening position Bolt
Drill bolt for pulley with assembly to
holes axle spacers prosthetic
a. Total time to complete operation(s) in hours 5 3 2 3
b. Labor rate for the operation ($/hr) 15 15 15 15
c. Labor Cost ($) = a x b 75 45 30 45
d. Basic overhead factor 1 1 1 1
e. Equipment factor 0.5 0.5 0.5 0.5
f. Special operation/Tolerance factor
g. Labor/Overhead/Equipment Cost ($) = c x
0.25 0.25 0.25 0.25
(1+d+e+f) 206.25 112.50 82.50 123.75
h. Purchased materials/Components cost 12.15 7.82 22.44 8.45
Total Labor/Overhead/Equipment Cost $ 525.00
Total Purchased Material/Components Cost $ 50.86
Total Cost for Assembly $ 575.86
7.4 Design Validation
Throughout our design and manufacturing phases, interaction with our end user has shaped our
project, and allowed us to effectively address real-world considerations. Ultimately, three main
goals were set forth from analyzing our customer input: reduction of input force (to reduce strain
on the user’s body), increase in grip force (to allow the user to complete a wider variety of tasks
with the prosthetic), and to make the product both reliable and serviceable (so the customer can
fix it easily, if need be).
For the reduction of input force, we decided on a pulley-based mechanical advantage system
early on. This configuration guaranteed a 2:1 reduction in user input force, as well as twice as
much cable travel to get it open. Since this feature was most important to the user, and would
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