A procedure for creating actuated joints via embedding shape memory alloys in PolyJet 3D printing

Abstract

Additive manufacturing's layer-by-layer fabrication approach allows the user to access the entire volume of the part throughout the build process. This allows for the embedding of functional components and actuators to enable the fabrication of complex systems in a single process. A process for the embedding of shape memory alloy actuating wire within direct PolyJet 3D printed parts is presented in this article. A series of "Design for Embedding" considerations are presented for achieving successful and repeatable embedding results. These considerations include guide channel design, design of shape converters for irregularly shaped elements, and design of wire fixation points. The embedding process is demonstrated with two case studies: a simple compliant joint specimen with a straight shape memory alloy wire and an antagonistic joint design with spring-shaped shape memory alloys. The process is characterized through an exploration of the potential for surface defects in the final specimens, as well as basic quantitative and qualitative evidence regarding performance of the final embedded actuators.