Surface roughness and chip formation in high-speed face milling AISI H13 steel

Many previous researches on high-speed machining have been conducted to pursue high machining efficiency and accuracy. In the present study, the characteristics of cutting forces, surface roughness, and chip formation obtained in high and ultra high-speed face milling of AISI H13 steel (46-47 HRC) are experimentally investigated. It is found that the ultra high cutting speed of 1,400 m/min can be considered as a critical value, at which relatively low mechanical load, good surface finish, and high machining efficiency are expected to arise at the same time. When the cutting speed adopted is below 1,400 m/min, the contribution order of the cutting parameters for surface roughness Ra is axial depth of cut, cutting speed, and feed rate. As the cutting speed surpasses 1,400 m/min, the order is cutting speed, feed rate, and axial depth of cut. The developing trend of the surface roughness obtained at different cutting speeds can be estimated by means of observing the variation of the chip shape and chip color. It is concluded that when low feed rate, low axial depth of cut, and cutting speed below 1,400 m/min are adopted, surface roughness Ra of the whole machined surface remains below 0.3 mu m, while cutting speed above 1,400 m/min should be avoided even if the feed rate and axial depth of cut are low.