Electron Discharge Machining (EDM) and Hole EDM of Cold Heat treated Tool Steel Molds (STD11) by using Cu Electrodes
3D formed Electrical Discharge Machining (EDM) and hole EDM were conducted for die and mold manufacturing with electrodes which were made by mechanical machining and wire EDM. It is difficult to machine the hardened material after heat treatment and quenching with traditional machining. The only method of machining hardened material is die sinking EDM. In this research, hole EDM was conducted for heat treated cold worked tool steel (SKD11) for use as a die material. The EDM surfaces were analyzed by pulse on time and peak current of EDM current, according to the machining conditions of EDM. The EDM surface profiles were affected by the peak current. The contribution of each factor is peak current (91.63% and pulse on time (0.93% The best surface roughness was obtained with a 130 ms pulse on time and a 14.2 A peak current. With uniform EDM processing, the surface deteriorated with increasing pulse on time and peak current. The thickness of the solidified layer induced by EDM was increased as the peak current, crater shapes, and erupted shapes of EDM surfaces were increased. Therefore, microcracking gaps induced by surface tension were increased.