One pole of the pulse power supply of the EDM is connected to the tool electrode, and the other pole is connected to the workpiece electrode, and both poles are immersed in the liquid medium with a certain degree of insulation (commonly used special spark oil). The tool electrode is controlled by the automatic feed adjustment device to ensure that the tool and the workpiece maintain a small discharge gap (0. 01 to 0. 05mm). When the pulse voltage of the EDM is added between the two poles, the liquid medium at the nearest point between the poles will be broken down under the conditions at that time to form a discharge channel. Because the cross-sectional area of the channel is very small, the discharge time is very short, resulting in a high concentration of energy (10 ~ 107W/mm), the instantaneous high temperature generated by the discharge area of the EDM is enough to melt or even evaporate the material, resulting in the formation of a small pit. After the end of the first pulse discharge, after a very short interval, the second pulse of the EDM hits the discharge between the other electrode recently. This cycle is repeated at a high frequency, and the tool electrode is continuously fed to the workpiece, and its shape is eventually copied on the workpiece to form the desired machining surface. At the same time, a small portion of the total energy is also released to the tool electrode, resulting in tool loss.