Influence of Die Geometry on Tool Life in Endmilling of Hardened Steel
Iwao Yamaji, Yoshiaki Kakino, Soichi Ibaraki (Kyoto University)
Hidetoshi Otsuka (Oita Industrial Research Institute)
Hidenori Saraie (Mori Seiki Co. Ltd.)
Heizaburo Nakagawa (University of Shiga Prefecture)
High speed cutting of hardened steel SKD61(HRC53) became possible by the introduction of a sintered carbides endmill coated by (Al,Ti)N. According to machining experiments, typical tool life of this endmill cutter is about 320 m for straight line cutting. It becomes, however, only 30 m for inner cylindrical surface cutting of the radius ratio ro/r = 2 (r: cutter radius, ro: machined geometry radius), which is often used for the machining of die/mold. This short tool life is caused by the rapid increase of cutting force, temperature elevation on the cutting tool, and chip jamming, all of which are easily introduced at inner curve cutting. By applying the constant cutting force control technique, the tool life can be elongated to 110 m. To regulate the cutting force at a constant level, the feed forward control is used based on a mathematical model of cutting force.
Keywords:   Endmill, hardened steel, die/mold, tool life, constant force cutting