Single-Print Rolling Contact Joints to Minimize Fatigue in Additively Manufactured Prosthetic Fingers
Open Access
- Author:
- Wilson, Mary
- Area of Honors:
- Mechanical Engineering
- Degree:
- Bachelor of Science
- Document Type:
- Thesis
- Thesis Supervisors:
- Jared Butler, Thesis Supervisor
Margaret Louise Byron, Thesis Honors Advisor - Keywords:
- compliant mechanisms
rolling contact joint
prosthetics
prosthetic finger joints
engineering design
TPU
contact-aided joint
finger joints
additive manufacturing
3d printing
3d-print
mechanical design
fatigue analysis
joint fatigue - Abstract:
- Contact-aided compliant mechanisms allow for the reduction of friction and fatigue, which therefore have applications within the realm of additively manufactured joints used in prosthetic hands. These joints allow for two surfaces to roll against one another to ensure that applied forces are properly distributed and do not cause delamination of the printed material, nor break after a short quantity of cycles. Therefore, identifying ways for a joint with minimal fatigue to be 3D-printed with little assembly necessary simplifies the solution of additively manufactured prosthetic hands, and provides an accessible, cost-effective avenue for people to create and use prosthetic hands. This work identifies potential joint structures to use, how to 3D-print the joint including trials using many types of compliant mechanism joints and configurations, and provides a decision matrix that investigates which joints are the most promising to solve the fatigue problem within prosthetic fingers. After determining that the rolling contact joint performs the best, the iterative process of altering its design to simplify the manufacturing and assembly processes ensued and resulted in the development of a single-print rolling contact joint made from flexible thermoplastic polyurethane (TPU) material, despite the design constraints of using a 3D printer and additive manufacturing. Through conducting a fatigue analysis on the final single-joint prototype, this single-print rolling contact joint design is found to withstand approximately 10,000,000 cycles of bending, and allows for multiple joints to be connected in series and manufactured as one cohesive printed part per finger. These single-print prosthetic fingers are then able to be actuated with a cable attached to a motor to result in movement of the prosthetic fingers, acting similarly to a natural hand.