Design for manufacture and assembly of a polycentric paediatric prosthetic knee

Abstract

Design for manufacture and assembly is a critical step in the product design life cycle. In this study, design for manufacture and assembly theory was applied to the design of a polycentric paediatric prosthetic knee to resolve assembly and manufacture issues prior to product prototyping. Assembly time and efficiency prior and subsequent to design for assembly analysis was calculated. By combining redundant parts and improving the ease of alignment, orientation, and insertion of various parts through modification of part features, a 10.1% increase in assembly efficiency was achieved. Design for manufacture analysis was then performed for die casting of the component. Undercut features were removed and replaced with the use of standard components, reducing the assembly time of the component by reducing the complexity of parts. Proposed design changes were verified using finite element analysis to simulate the loading conditions of a polycentric prosthetic knee as per the ISO10328:2006 standard for methods of testing prostheses. An overall improvement of 13.6% in assembly efficiency was achieved after the design for manufacture and assembly analysis. The improvement is due to the decrease in assembly insertion time and eliminating small parts and parts in areas that were difficult to access. The reduction in assembly time will directly reduce the labour cost for assembly of the manufactured product. This case study illustrates how design for manufacture and assembly theory can be applied to the design of biomedical equipment to reduce the need for prototype re-work and the consequent costs.