Influence of external hydrostatic pressure on machining characteristics of electrical discharge machining

Electrical discharge machining (EDM) tests were conducted under various external hydrostatic pressure to investigate the influence of gas bubbles. High-speed camera observation of a single pulse discharge revealed that decreasing the hydrostatic pressure increased the bubble diameter and thus the bubble pressure decreases. Thus, the removal volume of a single discharge increases as the hydrostatic pressure decreases because of the lowered boiling point. However, the results of sinking EDM showed that the material removal rate is not determined solely by the removal volume of a single pulse discharge. This indicates that bubbles have a significant flushing effect on EDM processes.