Design rules for additively-manufactured wrist splints

Currently patients with wrist ailments may be prescribed wrist splints to aid in their treatment regime. The traditional fabrication process of custom-made splints is skill dependent, time-consuming and the splints themselves pose numerous problems with regard to patient compliance. To overcome this, the use of Additive Manufacturing (AM also known as 3D Printing) has been proposed in recent years and there has been an increase in public awareness and exploration. Many of these developments have been as a result of the Maker-movement, the Internet-of-Things and development of more accessible technologies and infrastructures to enable production of AM builds; hobbyists, industry and academia are exploring the use of AM in creating splints, all with strengths and weaknesses. One of the main weaknesses of most developments is the lack of acknowledgement of whether the lattice type designs with cut-out patterns are strong enough. To address this lack of validation, this research aimed to generate and evaluate design rules that allow for the creation of safe and effective wrist splints through a digitised splinting process for production using AM.

This research first investigated what variables of a lattice type design had a significant effect on the stiffness of a splint. This was done using Finite Element Analysis (FEA) and Design of Experiment (DoE) methods. Initial FEA results were verified using physical testing.

These results were then brought into the next study where they were optimised to gain a better understanding of the effect the variables have on the displacement response. Finally, these results were applied to different regions of the splint to create unique rules for each region of the splint, with the aim of creating a splint that is optimised for material use versus stiffness.

All results were collated and a set of design rules for AM splints produced using Laser Sintered PA 12 were created.