Clarification of EDM gap phenomena using transparent electrodes

This paper describes the heat source diameter of single pulse discharge in electrical discharge machining. To observe the discharge plasma, SiC and Ga2O3 single crystals were used as the electrode material since they are optically transparent and electrically conductive. It was found that plasma diameter expands within a few microseconds after dielectric breakdown and the plasma diameter is much larger than the discharge crater. From the measured diameter of the crater, the heat source diameter was obtained by solving the inverse problem of heat conduction analysis, and it was found that the heat source diameter is smaller than the plasma diameter but larger than the crater diameter.