Manufacturing and Prototyping

We wanted to be able to create a low-cost, lightweight, and reliable design. We focused on minimizing deflection at the full extension of our scissor design as we identified that as the most problematic area in our design. We decided to keep our tolerances as tight as possible as a result, and use precision machining where possible. 

When progressing from our conceptual models to actual prototyping and manufacturing, we had to find the optimal balance between ease of fabrication as well as cost and material stiffness. We found that 3D printing our parts in ABS plastic was not only the quickest and easiest method of realizing our ideas, but also produced linkages that were both lightweight and relatively stiff. To assemble these linkages together, the pins were machined to the specs shown to provide a tight fit for the snap rings and 1mm 3D printed spacers. The machining process involved turning down the 5mm rods slightly with sandpaper on a lathe so that they would fit into our bearings, grooving the slots to a depth of .018 inches, and then cutting the pins off with a saw. We had to grind a custom grooving tool for the slots for the snap rings. Although the narrowest cutting tip we could reach was .032 inches, it was still within tolerance and provided a tight fit for our snap rings.

Eventually, we would find that most of the deflection in our design would be a result of the RC bearings that we purchased from Amazon. While these bearings functioned as specified and helped us reach a low-cost design, there would be a noticeable droop at the connection point of each linkage. The rest of the pins for the gears, servos, and slider rails were cut, deburred, and chamfered in the machine shop. Bearings were press fitted, and all items were fixed with superglue to reach our final assembled product.