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The first prototype for the retraction mechanism was 3D printed from ABS plastic, and the final prototype was made of laser cut acrylic. At first, the ease and versatility of the 3D printing process seemed to be the most desirable manufacturing method. However, the tolerancing of the machines that our group had access to was lacking, and we decided to move to a different material and process. Acrylic was selected because it is relatively lightweight compared to other materials readily available, and still easy to rapidly manufacture using a laser cutter. In order to replicate the original finger and its capabilities , and have the replica directly comparable to the original gripper design, we needed to manufacture small linkages with very delicate parts needed to be manufactured. This proved , and we knew that this would be challenging with acrylic material due to its (acrylics) 's low impact and rupture strength. All of the gears and links were laser cut from acrylic, for speed of prototyping, and cost. Due to this choice of material, we found assembling the linkages difficult, with many parts breaking without proper care.In spite of this, the benefits listed above outweighed the costs.
We purchased pre-made plastic gears online for the spur gear train between the motor and finger. They were more durable than the finger gears and did not break.