Formation Process of Molten Residual Layer in a Single Discharge Crater

Electrical discharge machining (EDM) removes material through the accumulation of small discharge craters formed by individual discharges. To improve machining characteristics, it is essential to enhance the efficiency of material removal during a single discharge. However, not all of the material melted by the discharge is removed; a significant portion remains on the workpiece. Therefore, accurately quantifying the amount of melted material removed during a single discharge and selecting appropriate machining conditions based on these results are crucial. In this study, the residual molten layer beneath the discharge crater was examined using slice polishing, and a discharge crater profile, including the residual molten layer, was created based on the observations. The obtained shape profile was used to evaluate the formation process of the molten residual layer over the course of discharge time, and the formation process of the discharge crater during a single discharge was analyzed. Furthermore, the removal efficiency of a single discharge under the same energy conditions was also investigated.