Investigation into the effects of milling input parameters on the material removal rate and surface roughness of polypropylene + 80 wt. % quarry dust composite during machining

This paper presents a study that focused on the utilisation of Taguchi optimisation of spindle speed (N), feed rate (F), and depth of cut (D) towards the surface finish (Ra) and material removal rate (MRR) during the computer numerical control (CNC) milling operation of a novel polypropylene (PP)/quarry dust composite. This study is essential in the determination of the levels to use for the input parameter of the machining (N, F and D) in order to produce a final product of the novel composite material having good surface integrity at reduced production cost and time. The design of the experiment (DoE) was conducted using the Taguchi technique, and an L₉ orthogonal array (OA) was used in carrying out nine sets of CNC milling operations. The surface roughness test was then carried out on the machined surface, and the MRR was determined. Additionally, microscopic images of the milled surfaces were taken. The statistical analyses were carried out using analysis of variance (ANOVA), regression analysis, and contour analysis. Results showed that the optimum parameters for speed, feed rate, and depth of cut were 400 rpm, 120 mm/min, and 0.9 mm, respectively, for the MRR and 800 rpm, 120 mm/min, and 0.3 mm, respectively, for the surface roughness.