Material Selection

<< Final Prototype: Variable Ground Link (VGL) Parallelogram 4-Bar Retractor

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, and we knew that this would be challenging with acrylic's  low impact and rupture strength. In spite of this, the benefits listed above outweighed the costs.

Where durability mattered most, we purchased pre-made plastic gears online for the spur gear train between the motor and finger. These injection molded plastic gears were tougher through repeated use than the acrylic finger gears, and did not break. 

>> Results, Conclusion, and Further Work