Upper Arm Casing

thingiverse

This is the upper-arm casing for Sophie's double-jointed arm. It fits snugly over an internal 'bone' of 20x20mm aluminium extrusion that I designed with precision. Internal flanges secure it in place, ensuring a stable fit every time. However, due to an issue with the CAD model in Fusion 360, one internal flange often fails to print - instead, it appears as a support structure. Although this is not a significant problem, since three other flanges provide sufficient grip, plus extra space inside the arm for wiring if needed. When printing, I enable raft mode so that the bottom of the arm casing doesn't warp or deform. The length of the aluminium upper arm 'bone' measures 178mm. To complete the assembly, visit these Thingiverse links: the shoulder joint is available at https://www.thingiverse.com/thing:4295678 and the elbow joint can be found here: https://www.thingiverse.com/thing:4296037. To secure the elbow joint in place, I drill a hole through Charlie's end, then insert a screw that bites into the aluminium extrusion. Next, I cut a small notch above the back of the elbow joint on the upper arm casing. This notch allows the upper arm casing to rest on the screw and stay securely in place.