Our final design functioned as desired; however, there is still work left to be done before this mechanism can be useful to someone for daily wear. The final prototype heavily used PLA and ABS because they were cost effective and readily available building materials; however, in the long run, these are poor choices for daily use.

Slider

The wheels for the slider for example are PLA and will wear away very quickly. We would recommend that the wheels be remade with nylon to provide a smooth sliding contact with a longer lifespan without adding significant weight to the slider.

Guide

We 3D printed the helical guide rail along a wrist brace because fabricating such as small helical profile from metal was not practical for a prototype. The consequence of this was a bulky, unattractive wrist brace. This may be heavy for some users and does not breath well. After a short period of wear, the user will quickly start sweating. The 3D printed helix was also not desirable from a manufacturing perspective. It takes 13 hours per brace to print and the helix requires high precision printing to be an effective guide.

In addition, the current helical guide configuration considerably limits the range of motion of the user's elbow. This is because the analysis we performed did not account for the considerable size of the slider. By the time the edge of the slider reaches the edge of the guide rail, the users range of motion is limited to roughly 90 degrees of elbow bending.

Upper Arm Connection

The connection for the upper arm does not provide a true “ground” for the mechanism. As the user flexes his/her arm, the bicep will expand and contract beneath the upper arm connection. The current version of the connection grips the arm too firmly and shifts up and down as the arm flexes. This is uncomfortable for the user and could potentially pinch veins on the side of the arm. The user’s arm should be wrapped in foam and then fitted with a larger version of the connector. This would then be locked into place around the foam.