Optimization of CNC Milling of General-Purpose Poly (Methyl Methacrylate)

Abstract

Abstract The purpose of this study was to investigate the impact of CNC milling parameters on the material removal rate (MRR) and surface roughness (Ra) of the general-purpose PMMA. The milling parameters considered were cutting speed, axial depth of cut and feed rate, each having four levels obtained through experimental trial and error. The levels were 300 rpm, 700 rpm, 1300 rpm, and 2000 rpm for the cutting speed; 0.3 mm, 0.8 mm, 1.5 mm, and 2 mm for the axial depth of cut; and 50 mm/min, 100 mm/min, 200 mm/min, and 350 mm/min for the feed rate. The Taguchi technique was used to design the experiments and carry out the analysis and optimization with an L16 orthogonal array. From the analysis, the optimal milling parameters for the maximum MRR were a cutting speed of 300 rpm, an axial depth of cut of 2 mm, and a 350 mm/min feed rate. The optimal CNC milling parameters for the least Ra were obtained at a cutting speed of 2000 rpm, an axial depth of cut of 0.3 mm, and a 50 mm/min feed rate. An ANOVA conducted depicted that all three factors were significant towards the MRR with the feed rate having the highest percentage contribution (48.8%), followed by the depth of cut (38.3%), and lastly, the cutting speed (9.8%). An ANOVA for Ra depicted that cutting speed and feed rate were the most significant factors. The axial depth of cut was insignificant towards the mean surface roughness. In terms of percentage contributions to the mean surface roughness, the cutting speed had the highest contribution (59.9%), followed by the feed rate (19.4%), and lastly, the axial depth of cut (13.9%).