During EDM, the tool electrode and the workpiece are respectively connected to the two poles of the pulse power supply and immersed in the working fluid, or the working fluid is filled with the discharge gap. The feed of the tool electrode to the workpiece is controlled by the gap automatic control system. When the gap between the two electrodes reaches a certain distance, the pulse voltage applied to the two electrodes will break down the working fluid and generate spark discharge.
A large amount of heat energy is instantly concentrated in the tiny discharge channel, the temperature can be as high as 10000 degrees Celsius, and the pressure also changes sharply, so that a small amount of local metal material on the working surface is immediately melted and melted. Gasification, splashing into the working fluid in an explosive manner, quickly coagulates into solid metal particles in the process, which are taken away by the working fluid. At this time, the surface of the workpiece leaves tiny pit marks, the discharge is temporarily suspended, and the working fluid between the two electrodes is restored to the insulating state.
Subsequently, the next pulse voltage breaks down at another point where the two electrodes are closer to each other, generating a spark discharge, and the above process is repeated. In this way, although the amount of metal removed per pulse discharge is small, since there are tens of thousands of pulse discharges per second, more metal can be removed, with a certain productivity. In the case of maintaining a constant discharge gap between the tool electrode and the workpiece, the tool electrode is continuously fed to the workpiece while removing the metal of the workpiece, and finally a shape corresponding to the shape of the tool electrode is machined. Therefore, by changing the shape of the tool electrode and the relative movement between the tool electrode and the workpiece, various complicated profiles can be machined.
tool electrodes are usually made of electro-corrosion resistant materials with good conductivity, high melting point and easy processing, such as copper, graphite, copper-tungsten alloy, molybdenum, etc. During processing, the tool electrode is also lost, but less than the amount of metal erosion of the workpiece, or even close to no loss.
working fluid is used as a discharge medium and also plays a role in cooling and chip removal during processing. Commonly used working fluids are low viscosity, high flash point, stable performance media, such as kerosene, deionized water, emulsion, etc.