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

PhD ThesisSolid 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

Investigating the Effects of Assembly Order on the Performance in Relation to Cognitive and Physical Demands Under Takt Time

Assembly line operations generally involve physical and cognitive demanding tasks. Simultaneous performance under physical and cognitive demanding tasks may create physical and mental stresses. A within subjects study was carried out to determine the effects of assembly levels (variable assembly and consistent assembly) on working conditions. Nine participants participated in a study and performed 8 conditions. The objective of the study was to determine the relation between physical and cognitive demands in a simulated task involving simultaneous performance of physical (fastening nuts and bolts) and cognitive (code matching with secondary task of memorizing the code) demanding task. Results showed the significant effects of assembly order (consisted of the concurrent performance of physically and cognitively demanding task) on the working conditions. Quality of performance was affected by variable assembly order, high mental demand and above shoulder heigh

Predictions of Buoyancy-induced Flow in Asymmetrical Heated Rotating Cavity System

This paper presents the finite difference solutions for buoyancy-induced flow in the asymmetrical heated rotating cavity system for the range of rotational Reynolds numbers Reθ =6.13x10^5 <Reθ =4.4x106 and the mass flow rates Cw<28000<Cw < 3000. All the simulations have been carried out through the CFD (Computational Fluid Dynamics) commercial code, ANSYS Fluent 12.0, by adopting axisymmetric, Steadystate and elliptic technique. Two well know models namely k-ε and the Reynolds stress models have been employed. The simulated results illustrate the important aspects of the heated rotating cavity flow system. The noteworthy influence of buoyancy-induced flow have been observed on the predicted stream lines, static temperature contours and the local Nusselt numbers for the rotating cavity space. A comparison of the predicted local Nusselt numbers for the hot and cold discs showed a good level of agreement with the measurements