Bottom Cutting High-speed EDM using Cu-hybrid Thin Plate Electrodes

抄録

In die-sinking electrical discharge machining (EDM), pulsed discharges are repeatedly generated between the electrode and workpiece, whereby small discharge craters are repeatedly formed on the workpiece as machining progresses. The machining speed is low in this process because all removed parts are discharged as debris. High-speed EDM was previously attempted using a water-based machining fluid with a high-current discharge of approximately 1000 A with a water-based machining fluid. However, this method is impractical because of electrode wear, low machining accuracy, and high roughness of the machining surface. As another countermeasure, a scooping EDM method that uses a frame electrode was proposed. The machining speed is high because the removed part is processed as mass, not as debris. However, this method is only applied to zinc alloys because the frame electrode disappears with electrode wear. In this study, we propose bottom cutting EDM using a thin-plate electrode, which is theoretically resistant to electrode wear. Highly rigid stainless steel and phosphoric bronze were selected as electrodes to bend the thin-plate electrodes in the horizontal direction. However, using both electrodes is difficult because of the substantial electrode wear and unstable discharge state. Therefore, we devised a hybrid electrode in which a thin copper plate is attached to the tips of both thin-plate electrodes, further determining the attachment method and considering the conditions for stable EDM.