Comparing surface roughness and tool wear when milling convex surface of hardened steel using different milling strategies

Abstract Regarding milling of dies and molds, there are several geometric requirements, and it is absolutely not trivial to machine complex either concave or convex surfaces. Since the contact between tool and workpiece changes all the time, making the components of the milling forces also to change, it is fundamental to find the correct milling strategies which cause the smallest variation of cutting forces (amplitude and sense) in order to obtain the best possible workpiece surface quality. In this work, four different machining strategies for finish milling of D6 tool steel were studied. They were compared in terms of surface roughness, cutting force, and tool wear at the end of tool life. Results show that lower surface roughness was obtained using descending down milling and ascending up milling because the sense of the cutting force components, specially the one that is normal to the machined surface on the most critic region of the workpiece, pulled the workpiece against the tool and the tool against the workpiece. On the other hand, descending up milling and ascending down milling did not present good results because the sense of the force components was responsible for excessive tool bending moving the tool and workpiece apart.