CNC milling of EVA foam with varying hardness for custom orthotic shoe insoles and process parameter optimization

Abstract

CNC milling strategy of EVA foam with varying hardness to provide a high degree of surface roughness of orthotic shoe insoles is presented in this work. Machining parameters (tool path strategy, spindle speed, feed rate, and step over) in addition to hardness material and wide tolerance insoles were optimized using a hybrid approach of Taguchi-Response Surface Methodology (TM-RSM). The aim of this research was to develop mathematical models and determine the optimum machining parameters which could be applied for the CNC milling of EVA foam as the insoles. Experiments were performed on a CNC milling machine with a standard milling cutter and run under dry coolants. The effects of the six parameters on the average values of surface roughness were initially analyzed by an S/N ratio of TM. Optimal conditions were established from the TM and then used to determine the optimum values in RSM modeling. The final results indicate the significant improvement of percentages (0.24% and 4.13%) in the surface roughness of the insoles obtained with TM-RSM as compared to the TM analysis. It is envisaged the present study would add to the understanding of production for orthotic shoe insoles through CNC milling.