Development and validation of a five-axis CNC machine tool for orthosis mold manufacturing

Abstract

This study aims to improve orthosis manufacturing by developing and validating a five-axis computer numerical control (CNC) machine tool to produce orthosis molds. The manufacturing of orthoses requires a high level of technical execution to ensure functionality and comfort for the wearer. Traditional methods, most notably the manual shaping of plaster casts, are time-consuming, prone to dimensional deviations, and labor-intensive. Although the introduction of CNC machines has improved the process, conventional serial kinematic CNC systems, commonly used for milling molds and orthotic blanks, are still limited in terms of flexibility, surface finish, and overall production time. As a potential solution to overcome these constraints, a prototype five-axis CNC machine based on parallel kinematics was developed to provide enhanced tool control, greater authority over the machining of complex surfaces, and shorter cycle times. The system was validated by comparison with specialized CNC and robotic solutions currently in use within orthotics and prosthetics practice, and by analyzing dimensional deviations, machining times, and surface quality. The research focused on foot orthosis molds, whose complex geometry and biomechanical demands pose challenges. Testing showed that the prototype achieved mean deviations of 0.15 mm, reduced the total lead time by roughly 10 % compared with classic CNC solutions, and significantly improved the surface finishing, while decreasing the need for manual post processing. These results indicate that parallel kinematic machines potentially apply to orthosis manufacturing and provide a basis for further research and system optimization.