Analysis of Discharge Location in Drilling EDM

In drilling EDM, the rotating motion of the tool electrode alters the gap between the electrode and the inner wall of the drilled hole, thus increasing the likeliness of producing lateral discharges. Lateral discharges do not contribute to the progress of the operation and deteriorate the quality of drilling in terms of precision and surface integrity. Hence it is crucial to detect and analyze lateral discharges and take appropriate measures to avoid or reduce them. In this paper, a metal structure is designed to hold a dowel pin as a cylindrical workpiece in such a way that the current is split into two paths, effectively forming a current divider. During the drilling process, two Rogowski coils measure current flowing through the upper and lower part of the cylindrical workpiece. Electrical modelling was performed to study the characteristic behavior of the currents. The discharge location can be correlated with the difference in current values. With the help of density plots, positions of individual discharges as well as a density of discharges for every location along the workpiece could be visualized and analyzed. Over the long term, live detection of lateral discharges can facilitate the design of control mechanisms which could minimize the impact of lateral discharges.