Investigation of the Fundamentals of Tool Electrode Wear in Dry EDM

The fundamentals of the tool wear in dry electrical discharge machining (DEDM) were investigated by plasma optical emission spectroscopy. Interpretation of the spectral lines suggests that single DEDM discharges with point-type cathode tool (Cu) and anode workpiece (Al) present characteristics of hot anode vacuum arcs (HAVA). The anode is active and the cathode is passive in a HAVA, which is probably the main reason for the relatively large workpiece erosion and very small tool wear reported for DEDM in the literature. The plasma characteristics change substantially inverting the electrodes polarity, thereby both electrodes have an active role in the discharge.