Time Variation and Mechanism of Determining Power Distribution in Electrodes during EDM Process

The aim of this study is to determine the mechanism of the power distribution in electrodes during the electrical discharge machining (EDM) process. The time variation of the power distribution is first measured by comparing the measured temperatures of the electrodes with the calculated results. It is found that, in the earlier stage of each pulse discharge, the measured power distribution in electrodes is at most two thirds of the total discharge power. As the discharge duration increases, however, the power distribution in electrodes approaches the total discharge power, which coincides with the solution of the magnetohydrodynamic equations for the EDM discharge plasma when the plasma is assumed to be in local thermodynamic equilibrium and in a steady state. It is concluded that, during the discharge duration normally used in the EDM process, the gap condition is not in equilibrium and a large fraction of the discharge power is consumed in transient phenomena such as evaporating, dissociating and ionizing of the dielectric fluid.