The need for custom-made devices, rehabilitation aids and treatments is explicit in the medical sector. Applications of rapid manufacturing techniques based on additive fabrication processes combined with medical digitising technologies can generate high quality solutions in situations where the need for custom-made devices and rehabilitation aids and low-lead times are very important factors. Foot orthoses are medical devices applied in the treatment of biomechanical foot disorders, foot injuries and foot diseases including rheumatoid arthritis and diabetes. The significant challenge in the treatment of foot related diseases is progressing pathological deterioration in the affected sites of the foot which requires quick provision of the orthoses. A process model is developed using the IDEF0 modelling technique in which a rapid manufacturing approach is integrated in the design and fabrication process of custom foot orthoses. The process model will be used in the development of rapid manufacturing based design and fabrication system for mass customisation of foot orthoses. The developed system is aimed at mass scale production of custom foot orthoses with the advantages of reduced cost, reduced lead-time and improved product in terms of increased fit, consistency and accuracy in the final product.