Study on the Machinability of SMC Composites During Hole Milling: Influence of Tool Geometry and Machining Parameters

The machining of composite materials is generally performed to obtain the required geometry and dimensional tolerances. This paper applies the Taguchi method to investigate the effects of end-milling parameters on the machinability outputs of chopped glass fiber-reinforced polymer composites. The main aim is to investigate the machinability and defects generated by four different end-mill tool geometries when applying hole expansion on A-Class Sheet Mold Compound (SMC) composites. The resultant force, surface roughness, and peel-up delamination behavior were evaluated under different cutting conditions in milling operations, while the milling experiments were conducted under different parameters and levels according to the Taguchi method. The contribution ratio of parameters on machinability outputs was analyzed statistically via analysis of variance and regression analysis. The most suitable cutting conditions to achieve a high-quality hole in the least amount of machining time on an SMC composite include higher cutting speed, lower feed rate, higher number of teeth—as with six-fluted helix and eight-fluted burr-style end mills—and down-milling with CCW circular interpolation.