Introduction to a Type of Resin-Reinforced Rapid Prototyping Transtibial Socket

Abstract

This article introduced a type of rapid prototyping (RP) transtibial socket that is fabricated by a fused deposition modeling (FDM) machine and wrapped with a layer of unsaturated polyester resin (UPR) to enhance its flexural strength. As current rapid prototyping machines use a layer-based process to manufacture products, this will result in RP products liable to break along forming layers once bending moment is applied. To prevent RP prosthetic socket from breakage, this study proposed wrapping a layer of unsaturated polyester resin around a preliminary thin RP socket to reinforce its flexural strength. Factors affecting the strength of the resin-reinforced RP socket include thickness and forming orientation of the preliminary RP socket, thickness of the UPR layer, and type of material used to make the preliminary RP socket. Employing Taguchi experimental design method and ASTM three-point bending test standard, the parameters that influence the flexural strength of the resin-reinforced RP prosthetic socket can be determined. Based on the appropriate parameters, including thickness of the RP layer and UPR layer, the RP material and RP fabricating orientation, the preliminary thin RP prosthetic sockets can be fabricated by an FDM machine. And the thin layer preliminary RP sockets were then wrapped with cotton socks and laminated UPR layer to form resin-reinforced RP sockets. To confirm the effectiveness of the resin-reinforced sockets developed in this study, the pressures at residual limb/socket interface were measured by using a pressure distribution measurement system and movement was captured by a motion analysis system while a patient wears the resin-reinforced RP socket. Two resin-reinforced RP sockets have been fabricated and tested by a volunteer amputee. Analysis of the experimental results would assist a prosthetist to assess the distribution of interface pressures at the pressure-tolerant (PT) and pressure-relief (PR) areas of the residual limb. And, the gait pattern will be used to evaluate the applicability while the resin-reinforced RP socket is worn. Trial uses for durability test of the proposed RP socket are being arranged.