High-Speed Imaging of EDM Gap Phenomena using Transparent Electrodes

In electrical discharge machining (EDM), discharge occurs with a high frequency in a narrow gap space between parallel plane electrodes filled with a dielectric fluid thus making direct observation of electrical discharge phenomena extremely difficult. On the other hand, SiC single crystals are electrica lly conductive and optically transparent. This paper describes observation of the EDM gap phenomena through the transparent electrode from the direction normal to the discharge surface using a high speed camera. In consecutive pulse discharges, distribution of discharge locations and volume fraction of bubbles in the working gap were clarified.