Percentage of harmful discharges for surface current density monitoring in electrical discharge machining process

Abstract

Electrical discharge machining (EDM) is performed in the gap between the workpiece (usually the anode) and the electrode (usually the cathode). The gap is filled with a dielectric and the pulses generated by a special generator cause an electrical breakdown in the gap. A breakdown discharge occurs which removes material from the workpiece. The EDM process has been used for more than 50 years, but the influence of the surface current density on the process stability is not well understood. The surface current density is very important in the case of the machining of rough surfaces where the highest material removal rate (MRR) is preferred. For a given eroding surface there exists an optimal electrical current at which the highest MRR is achieved. It is reported in the literature that the percentage of the discharges that are harmful to the EDM process depends on the surface current density in the gap. Thus, experiments were performed to find out the possibility of using the percentage of harmful discharges to monitor the surface current density of the EDM process.