Increasing displacement range in 3D printed compliant joints via bio-inspired slot patterns: An exploratory study

Abstract

Compliant joints own their motion performance to three main aspects: base material, geometrical design, and dimensions. When aiming to increase their motion range without affecting the overall assembly of the system in which they are employed, modifying the design or dimensions is not appropriate anymore. To overcome this, the current work presents a novel strategy for increasing the motion range of the split tube flexural pivots joint based on removing material from the complaint joint using two specific bio-inspired patterns. These bio-inspired patterns are based on the shells encountered in Testudines (tortoise) and Dasypodidae (armadillo). Then, these patterns were parametrized, and their effective mechanical properties evaluated on 3D printed samples. Features of the flexible region of the flexural pivot joint were varied to identify the conditions in which the motion range increases. A factorial analysis was made to obtain the angular displacement response based on the determined parameters, which depend on the flexible region features. The use of these patterns successfully demonstrated the reduction in stiffness of the joints, obtaining increments in displacements twice in the stiffest case and 4.25 times in the most flexible one. Secondary displacements were also analyzed. Displacements measured were characterized via computationally analyzed images and recordings. Finally, the mechanical properties measured were compared to computationally predicted properties via Finite Element Models. Predictions resulted in good agreement with the experimental measurements with errors below 10% in most cases and up to 15% in the worst cases. These were attributed to manufacturing defects in the samples.