STUDY OF THE EFFECT OF TOOLPATH AND MACHINING PARAMETERS ON SPHERICITY, SURFACE FINISH, AND DIMENSIONAL TOLERANCE OF POLYMER ACETABULAR CUPS

The study of cutting parameters, machining strategies, effects of the cutting tool on precision and final surface quality, are necessary to extend the useful life of prosthetic elements allowing to delay joint replacement. In this work, an experimental study of CNC milling machining of an internal liner acetabular cup with a diameter of 28 mm for hip prosthesis was carried out. The investigation was carried out through a Taguchi L9 design of experiments, analyzing the influence of 4 machining parameters with 3 levels and 2 replicates. The used tool is a ball mill with a diameter of 10 mm. The factors studied were the effect of the toolpath (vertical-horizontal parallel, spiral-radial, vertical-spiral parallel), depth of cut (0.5, 1.0, and 1.5 mm), spindle speed (146.6, 178.02, and 209.43 rad/s) and stepover (0.05, 0.075 and 0.15 mm) over average roughness, sphericity, nominal diameter tolerance and machining time. The smallest mean roughness (0.6436 mu m) was obtained considering a vertical- spiral parallel strategy, a depth of cut of 0.5 mm, a spindle speed of 209.43 rad/s, and a cutting stepover of 0.075 mm. Our finding suggests that the cutting parameters proposed through the design of experiments of this work can help to obtain the desired surface finish in acetabular liner components by machining, in accordance with the international standard ISO 7206-2.