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Yale OpenHand Project: Optimizing Open-Source Hand Designs for Ease of Fabrication and Adoption

Although grasping and manipulation are key aspects of a robotic system's functionality, researchers often only have a limited selection of end effectors compatible with their manipulator base. This may either restrict the robotic system's full range of capabilities or force researchers to compensate for the end effector's intrinsic mechanical disadvantages through compensatory, nonoptimal control strategies. Advances in three-dimensional (3-D) printing have enabled researchers to quickly customize mechanisms for specific tasks, but the end product is usually not intended for extended use. It would be beneficial to identify strategies to augment the capabilities of additive manufacturing techniques to allow the easy and inexpensive construction of durable and functional hardware. To that end, this article details work on the Yale OpenHand Project, a library of lowcost, 3-D-printed, underactuated hand designs for researchers to freely implement and modify for their own use cases. The designs use cast flexural joints made via the hybrid deposition manufacturing (HDM) process to produce robust, impact-resistant subcomponents and help account for the structural shortcomings of fused deposition manufacturing (FDM). Several of these design examples are presented, evaluated, and compared with commercial alternatives. We hope that providing an accessible and extensible set of open-source hand designs will improve the iterative design process and produce many more options for researchers to utilize.