Debris distribution and dielectric fluid flow within the machining gap in electrical discharge machining (EDM) are important factors related to stable and precision machining. Hence understanding of the debris removal process is essential in improving EDM process. In this research, electrode jump motion with different jump heights and speeds was investigated to comprehend its effect on the fluid flow and debris-fluid interaction. A simplified fluid dynamics model characterizing the motion of the square shape electrode was established to study theoretically the effect of electrode jump speed on the debris-fluid flow. A setup to realize the electrode motion was designed. The Z-axis equipped with a linear motor was used to provide high speed jump function. The flow images were recorded by a high-speed camera, and the flow of the debris inside the hole was captured for analysis. Analytical results show that the fluid pressure at the bottom region of the electrode would reduce with the increase of electrode jump speed. Bubbles are generated once this pressure falls below the vapor pressure of the fluid. For the square shape electrode, it is found from the experiment that bubbles are prone to occur when the machining depth is increased. The result also shows that debris can be excluded easier when the electrode jump height is larger than 1/4 machining depth. Furthermore, using a large jump height incorporated with an electrode jump speed near the critical speed of bubble generation results in the most effective debris removal. On the other hand, the flow field of a high aspect ratio thin and flat electrode is different from that of the square electrode. There is no bubble generated during high-speed jump motion. The findings of this paper can be taken as the basis for choosing appropriate parameters of electrode jump motion in EDM deep cavity drilling.
