High-speed observation of multi-channel phenomenon using glass coated with transparent high-resistance film

In electrical discharge machining (EDM), high-resistance tool electrode materials result in the occurrence of multiple discharge channels within a single pulse. This phenomenon is utilized to improve machining efficiency or surface roughness. However, the multiple discharge channels occur in a very short time and very narrow space, making it extremely difficult to observe it directly and thus there are many unknowns about its understanding. In this study, high-speed imaging was used to investigate the multi-channel discharge process by using the glass coated with a transparent high-resistance film. As results, the discharge channels were clearly observed due to the transparency of the glass and film, and the phenomenon of multiple discharge channels within a single pulse was detected due to the high resistance of the film. It was found that the smaller the discharge gap, the greater the number of discharge channels and the smaller the channel diameter. It was also observed that during multi-channel discharge, the number of discharge channels may change, and the energy of each channel is not the same.