Compliant Robotic Extruded Hand (CRxH)

Abstract

This project presents the Compliant Robotic Extruded Hand (CRxH), a 3D-printed monolithic compliant robotic hand designed as a low-cost and easily replicable platform for prosthetic research and expendable manipulation in hazardous environments. The primary goal is to achieve human-like finger flexion through compliant underactuated structures that bend under low force while preserving structural integrity and elastic recovery (“shape memory”) over repeated use. The hand was iteratively designed to localize bending in compliant regions akin to the human hand and to prevent permanent deformation after repeated actuation. The anatomically inspired tendon routing facilitates realistic multi-joint finger curling, enables coordinated hand motion, and decreased assembly complexity. Strength tests found the hand to have a static strength capacity of at least 75 lbs, with each finger supporting at least 25 lbs. Qualitative dexterity tests found CRxH capable of mirroring numerous human actuation patterns and grasping various objects. The final hand prototype achieves 14 degrees of freedom, approaching the 21 degrees of freedom of the human hand. This repeatable motion is achieved without permanent plastic deformation. Thermoplastic Polyurethane (TPU) was chosen for the hand to support flexibility and compliance, while Polylactic Acid (PLA) was used for the rigid forearm motor housing. Both filaments can be 3D-printed with minimal client-side debugging. CRxH serves as an important stepping stone for future work on compliant, underactuated mechanisms for robotic manipulators by opening the door to improvements in accessible and rapid monolithic 3D-printed designs, highlighting grasping capability, closed-loop control, and autonomy. CRxH is able to provide comparable dexterity and a higher strength performance at a fractional cost compared to state-of-the-art commercial and research designs, accomplished in a single print.