EDM machine content and principle

Electrical discharge machine, referred to as EDM, is a mechanical processing equipment mainly used for electrical discharge machining. It is widely used in the manufacture of various metal molds and mechanical equipment. Electrical discharge machine is a special processing method that uses the electro-erosion effect generated by pulse discharge between two electrodes immersed in the working fluid to erode conductive materials. It is also called discharge machining or electro-erosion machining, referred to as EDM in English.

Principle
During electrical discharge machining, the tool electrode and the workpiece are connected to the two poles of the pulse power supply respectively and immersed in the working fluid, or the working fluid is filled into the discharge gap. The tool electrode is fed to the workpiece through the gap automatic control system. When the gap between the two electrodes reaches a certain distance, the pulse voltage applied to the two electrodes breaks down the working fluid and generates spark discharge.
A large amount of heat energy is instantly concentrated in the fine channel of discharge, the temperature can be as high as more than 10,000 degrees Celsius, and the pressure also changes sharply, so that the local trace amount of metal material on this working surface is immediately melted and vaporized, and splashed into the working fluid explosively, and quickly condensed to form solid metal particles, which are taken away by the working fluid. At this time, a tiny pit mark is left on the surface of the workpiece, the discharge is briefly paused, and the working fluid between the two electrodes returns to an insulating state.
Immediately afterwards, the next pulse voltage breaks down at another point where the two electrodes are relatively close, generating spark discharge, and repeating the above process. In this way, although the amount of metal removed by each pulse discharge is very small, because there are thousands of pulse discharges per second, more metal can be removed, and it has a certain productivity.
Under the condition of maintaining a constant discharge gap between the tool electrode and the workpiece, while the workpiece metal is removed, the tool electrode is continuously fed to the workpiece, and finally a shape corresponding to the shape of the tool electrode is processed. Therefore, as long as the shape of the tool electrode and the relative movement between the tool electrode and the workpiece are changed, various complex surfaces can be processed. Tool electrodes are often made of electro-corrosion-resistant materials with good conductivity, high melting point, and easy processing, such as copper, graphite, copper-tungsten alloy, and molybdenum. During the processing process, the tool electrode also has loss, but it is less than the amount of metal removed from the workpiece, and is even close to no loss.
As a discharge medium, the working fluid also plays a role in cooling and chip removal during the processing. Commonly used working fluids are media with low viscosity, high flash point and stable performance, such as kerosene, deionized water and emulsion. The EDM machine is a self-excited discharge with the following characteristics: There is a high voltage between the two electrodes of the spark discharge before the discharge. When the two electrodes are close, the medium between them is broken down, and then the spark discharge occurs. With the breakdown process, the resistance between the two electrodes decreases sharply, and the voltage between the two electrodes also decreases sharply. The spark channel must be extinguished in time after a short period of time (usually 10-7-10-3s) to maintain the "cold pole" characteristics of the spark discharge (that is, the heat energy converted by the channel energy cannot be transmitted to the depth of the electrode in time), so that the channel energy acts on a very small range. The effect of the channel energy can cause local corrosion of the electrode. The method of using the corrosion phenomenon generated during spark discharge to process the size of the material is called EDM machining.