1. Ionization of polar medium, breakdown
The ionization and breakdown of the inter-polar medium form a discharge channel, the tool electrode and the workpiece electrode are gradually approached, and the electric field strength between the inter-polar increases. Because the microscopic surfaces of the two electrodes are uneven. Therefore, the electric field is the largest at A and B where the distance between the two poles is the closest. There is a liquid medium between the tool electrode and the workpiece electrode. The liquid medium inevitably contains impurities and free electrons. Under the action of a strong electric field, they form negatively charged particles and positively charged particles. The greater the electric field strength, The more charged particles, eventually lead to ionization and breakdown of the liquid medium, forming a discharge channel.
2. After the melting and vaporization of the electrode material, the thermal expansion liquid medium is ionized and broken down, and after the discharge channel is formed, the negatively charged particles between the channels run towards the positive electrode particles and collide with each other. A large amount of heat is generated, so that the channel instant pupa is covered to a very high temperature. The high temperature of the channel first vaporizes the working fluid, and then the high temperature spreads around, so that the curved metal material on the two electrode surfaces begins to melt until it boils and vaporizes. The volume of the vaporized working fluid and metal vapor increases instantaneously, forming the characteristics of an explosion. Therefore, when observing the machining of the Cnc machine tool, it can be seen that the workpiece and the tool electrode have smoke and a slight explosion sound is heard.
3. Throwing of electrode material
The spark phenomenon generated between the positive and negative electrodes makes the discharge channel generate high voltage. The pressure in the center of the channel is the highest. After the working fluid and metal are vaporized, they continue to expand outward, forming an instantaneous pressure difference between the inside and outside. The molten metal liquid and vapor at the high pressure are pushed out and thrown out of the discharge channel, and most of them are thrown into the working fluid. A closer look at the EDM can see orange-red sparks flying around. This is the hot metal droplets and debris being thrown.
4. Deionization of polar media
If the galvanic corrosion products generated during the discharge process of the Cnc machine tool are not removed and diffused in time, the heat generated will not be transmitted in time. The local overheating of the medium will cause the locally overheated working fluid to decompose and form carbon at high temperature, making the processing impossible. And burn out the electrode, so in order to ensure the normal processing of the Cnc machine tool, there must be enough time between the two discharges to allow the galvanic corrosion products to be fully discharged, restore the insulation of the discharge channel, and deionize the working fluid medium.