Proto 1.0 was built in September 2018 to make sure the novel cable system is functional. This arm featured only 2 segments to prove a concept. Acrylic is used for the entire frame, for its transparency and easy laser-cutting. Skate bearings are used just to get things moving.

Lessons learned: tolerance matters on the bearings. Need to raise the base height for weights to swing openly. Not enough structural stability in the arm segments. Developed procedure to test and make sure that the 3D print settings fit the bearings, before printing everything.

Proto 2.0 was built shortly after 1.0 to iterate and fix all the immediate issues present. This time around we used wood to reduce costs, and actually linked the cables together to get a moving arm. There are still only two segments to ensure the cable system works. Bearings were reused on this version. Further developed work flow.

Lessons learned: pivoted to scaling down the arm for internal-body operation instead of external. Found that wood tends to loosen up after tightening; wood frame is slightly reduced after prolonged tension from the cables. 3D printed parts seem to work well for pulleys, and the counterweight adjustment mechanism works well also.

Proto 3.0 is currently underway. We have completed all CAD and laser-cuts for frames, and are in the final steps of gathering all hardware for the construction from vendors. Software tracking algorithms are already being cooked up and refined. Potential obstacles are currently building a linear actuator (they are $200 a piece out-of-box!) and shipping times. And of course, we have our impending symposium countdown!

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