Design and Analysis on the friction characteristics of a 3D printed mechanical synovial joint

Exploring the parameters of a novel 10DoF synovial finger joint

Master thesis (2023)

Authors

Y. van Delft Mechanical Engineering

Contributors

G. Smit Medical Instruments & Bio-Inspired Technology - Mechanical, Maritime and Materials Engineering (supervisor 1)
Faculty
Mechanical Engineering
Copyright: © 2023 Youri van Delft
Synovial joint Coefficient of friction Mechanical finger joint Artificial joint
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Published Date

03-07-2023

Language

English

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Faculty

Mechanical Engineering

Abstract

Background: Through technological development, a variety of mechanical finger joints have been produced. No current design takes inspiration from nature enough to develop a synovial inspired single finger joint. Due to this the potential performance is unknown, while natural joints out perform mechanical finger joints with respects to the coefficient of friction.

Goal & Research question: The goal is to construct a novel 3D printed 1-DOF mechanical synovial proximal interphalangeal(PIP) joint to explore the parameters of influence. In the exploration of these parameters, the following research question is formulated: To what extend does each of the following variables effect the coefficient of friction, the joint stiffness and hysteresis of a synovial joint? In which the material selection, contact surface roughness, capsule influence and fluid selection is considered.

Methods: Design requirements and performance criteria were formulated to guide the design process, from which the final design was generated. The design was measured with an optical profilometer to determine the surface quality and the performance evaluated with a custom build friction test bench.

Results: Through the process of this paper, a novel 1-DOF mechanical synovial joint was designed with a range of motion of 100 degree, along with a proof of concept design with 100 degrees in flexion and 8 degree in hyperextension. The synovial joint was successfully tested to access the performance and evaluate to which extend each of the parameters stated in the research question effected the performance.

Conclusion: The joint was successfully produced and allowed for evaluation of the desired parameters. Overall, the contact surface material and the contact surface roughness are the main contributors to the performance of the joint. The capsule has mixed influence while the lubrication shows some improvement with coated low roughness samples over the dry friction conditions. For all other cases the dry sliding baseline joints outperform the encapsulated lubricated joints.