Localization of Discharges in Drilling EDM Through Segmented Workpiece Electrodes

In drilling EDM different flushing methods and electrode geometries are applied to improve the process stability and avoid form deviations as a consequence of discharges in the lateral working gap. These methods are usually reviewed indirectly by determining target parameters of the process, the tool electrode or the bore hole. A localization of discharges along the bore hole however provides a quantitative measure for the ratio of discharges in the frontal and lateral working gap. This paper presents a setup for localizing discharges by use of a workpiece electrode consisting of electrically insulated segments and performing signal analyses. Tool electrodes with interior and exterior flushing channels are analyzed with this experimental setup to compare the effectiveness of the resulting flushing conditions. It was found that the use of a helix tool electrode leads to an increased material removal rate by at least 11% and a considerable reduction of lateral discharges.