Cost modelling of rapid manufacturing based mass customisation system for fabrication of custom foot orthoses

Abstract

Solid freeform fabrication (SFF) or Additive manufacturing (AM) techniques have emerged in recent years as advanced manufacturing techniques. These techniques have demonstrated advantages particularly in situations where the demands for unique geometrical structured customer-specific products are high and the time to market is very short. Applications of these techniques in the medical sector in combination with the latest medical digital imaging technologies are growing quickly. The techniques have inherent advantages of compatibility with the output information of medical digitising techniques.

Foot orthoses are medical devices used as shoe inserts in the treatment of foot disorders, injuries and diseases such as diabetes, rheumatoid arthritis, congenital defects and other foot related injuries. Currently custom foot orthoses are fabricated through manufacturing techniques which involve costly and based on lengthy trial and error manufacturing process. These techniques have limitations in terms of fabricating required geometries and incorporating complex design features in the custom-made orthoses.

The novelty of this research is to explore the commercial scale application of rapid manufacturing techniques and to assess a rapid manufacturing based design and fabrication system for production of custom foot orthoses. The developed system is aimed at delivering the custom made orthoses at mass scale with improved fit, consistency, accuracy and increased product quality.

The traditional design and fabrication process for production of custom foot orthoses was investigated and modelled with IDEF0 modelling methodology. The developed IDEF0 model was re-modelled and then the rapid manufacturing approach was integrated in the design and fabrication process. The main functions of foot geometry capture, orthoses design and manufacture of orthoses were modelled and evaluated individually with respect to time and cost and quality of the final product. Different well-established rapid manufacturing techniques were integrated in the current design and fabrication process. The results showed that the techniques have significant impacts on the overall design and fabrication process in terms of increased process efficiency, low lead-time, increased productivity and improved quality of the final product.

An orthosis model was fabricated on an experimental basis using different well established rapid manufacturing techniques. The techniques were separately investigated and analysed in terms of orthoses fabrication cost and build time. The cost and lead-time in different techniques were modelled, analysed and evaluated for evaluation of commercial scale applications. The analysis and evaluation of the cost and lead-time modelled for different rapid manufacturing techniques showed that selective laser sintering technique is the better option for integrating the technique in fabrication of custom foot orthoses and that it has the potential to compete with conventional techniques.