A Method to Enhance the Depth-to-Diameter Ratio of Micro-Holes Drilled with EDM Using the Pressure Difference Created at the Hole Entrance

Blind micro-hole drilling is an important application of electrical discharge machining. As the micro-hole depth increases, the viscous resistance of dielectric increases, causing difficulties in the removal of debris and bubbles from the interelectrode area and leading to their accumulation. The frequent abnormal discharges due to the bubble and debris accumulation leads to a decrease in the drilling feed rate, increase in tool wear, and limits the drilling depth. In this study, a method is proposed for the timely removal of bubbles and debris from the interelectrode area using a pressure difference created by restricting the dielectric flow channel based on Bernoulli’s principle. Simulations verify that the pressure difference can promote the flow of the dielectric in the narrow interelectrode area. In addition, experimental results show that not only the depth-to-diameter ratio and drilling speed are improved, but also that the electrode wear is reduced. These findings are helpful for understanding the mechanism of dielectric circulation in micro EDM and meeting the increasing demand for micro hole drilling in industrial field.