Influence of alternating side gap on micro-hole machining performances in micro-EDM

In the machining of micro-hole by micro-EDM, the narrow and uniform side gap leads to the difficulty in removing discharge debris from the working area, which causes frequent occurrence of abnormal discharges such as short circuit. In this study, a three-dimensional model with alternating side gap was proposed, based on which the flow field and movement of discharge debris in working gap were analyzed. Simulation results showed that the alternating side gap changed the flow field pattern in bottom gap, and the flow velocities both in bottom gap and side gap were increased as the enlargement of eccentric radius. In addition, when the alternating side gap was adopted, the concentration of debris particles in the bottom gap was dramatically decreased due to the improvement of flow field in the working gap, and the percentage of escaped debris particles was increased. Verifying experiments were carried out and the influences of alternating side gap on the micro-hole machining performances were addressed, which showed that both the material removal rate and aspect ratio of micro-hole were improved as the eccentric radius increases. Nevertheless, the eccentric radius still needs to be determined reasonably in consideration of the wear of electrode.