Study on energy distribution of discharge plasma and its effect on crater formation in EDM

Heat source and pressure source from discharge plasma to electrodes of electrical discharge machining (EDM) are key factors in the analysis of material removal process. To determine the role of distribution of the heat source and pressure source of EDM, this study uses particle-in-cell with Monte Carlo collision (PIC-MCC) simulation to calculate the energy distribution of discharge plasma. The distribution of the energy transfer on the electrode surface as well as heat source and pressure source is further obtained. The results show that the central peak value of the heat source decreases while the diameter increases with the increase of current, which is different from the assumed heat source distribution. A double Gaussian heat source is proposed to quantify the heat source under different conditions. The pressure source is in continuous oscillation so that it cannot be summarized as a stable distribution. Furthermore, the simulation of material removal process with double Gaussian heat source and pressure source of numerical results shows that the ejection of molten metal contributes to the dominant material removal. The width of crater increases with the increase of discharge energy, but the depth keeps constant of dozen microns. Regardless of the discharge energy, more than two-thirds of the molten material in the molten pool cannot leave the electrode surface. The experimental results of morphology of the crater are in agreement with the simulation results, meaning the model provides a more sophisticated energy input for analysis of material removal process in EDM.