Elucidation of gap area phenomenon in micro EDM drilling through direct observation

Abstract In micro EDM, the discharge is significantly influenced by the bubble behavior. The depth-dependent characteristics of bubble behavior play a key role on the dielectric exchange and debris exhaust. However, the difficulty of direct observation on the narrow gap area is a big obstacle in clarifying the bubble behavior in the gap area. In this paper, a method is put forward to both directly observe the behavior of bubble in the interelectrode gap area and the behavior of bubble escaping from the micro hole based on the self-designed SiC sandwich workpiece in the micro hole drilling with EDM. The aim is to comprehensively investigate the bubble behavior by combining the observation of bubbles in the interelectrode gap area with the bubbles escaping from the micro hole. The observation was performed by a high-speed camera at high frame rate. Depending on the proposed methods, the influence of bubble behavior on the micro hole drilling with EDM is comprehensively analyzed.