Optimisation of the machining time required by insole orthotic shoes for patients with clubfoot using the Taguchi and response surface methodology approach

In this study, the application of the computer-aided reverse engineering system (CARE) to the novel design and manufacture of a comfortable insole for a clubfoot patient is presented. The Taguchi method (TM) and response surface methodology (RMS) were used to predict the machining time of the orthotic boot insole during both computer-aided manufacturing (CAM) simulation and computer numerical control (CNC) machining. Taguchi’s experimental design, presented as a matrix orthogonal array L(27)3(6), was acquired for controlling parameters, namely tool path strategy (A), spindle speed (B), step-down (C), step-over of the cutter (D), cutter diameter (E), and dimensional tolerance (F) of the insole size. In this method, the model generated by the RMS method evaluates the six parameters influencing the machining time. The objective of this study is to develop a regression model that demonstrates the relationship between the cutting parameters and insole machining time. The optimal parameters are A(1)B(1)C(3)D(2)E(1)F(2), where A(1) denotes raster finishing, B(1) denotes a spindle speed of 10,000 rpm, C(3) denotes a step-down of 850 mm, D(2) denotes a step-over of 0.25 mm, E(1) denotes a cutter diameter of 20–35 mm, and F(2) deontes a tolerance of 0.75 mm. The experimental and calculated machining time (t(m)) results were 236 and 125.4 min, respectively. However, the real machining results were 334 and 152.25 min with error values of 46.86% and 54.42%, respectively. Meanwhile, with the t(m) RMS method, the simulated and calculated machining time results were 189.22 and 236.35 min, whereas the real t(m) values were 236.52 and 334.86 min with error values of 19.94% and 29.37%, respectively. This research obtains improvements of 19.82% (simulation time) and 29.19% (real-time).