Observation of Material Removal from Discharge Spot in Electrical Discharge Machining

In this paper, we observed the moment of material removal from a discharge spot using a high-speed video camera to investigate the material removal phenomena and the scattering behavior of debris particles in the electrical discharge machining process. Since material removal occurs not only during the discharge duration but also after the discharge duration, the observation of material removal occurring after the discharge duration was first carried out without inference from the strong light from the arc plasma. Then, material removal occurring during a discharge duration was investigated. In this experiment, a discharge is ignited on the front side of a foil electrode and the back side of the foil electrode was observed with blocking out the strong light from the arc plasma. The observed results show that there are different types of material removal that simultaneously occur in a pulse discharge. One is caused by the explosive evaporation of molten metal and the other is caused by the undulation of the molten metal. It is also found that debris particles removed during the discharge duration are small and their flying speed is high, whereas those removed after the discharge duration are large and their flying speed is low.