EDM graphite electrode
1. What is EDM:
Electric spark is a self-excited discharge. Its characteristics are as follows: the two electrodes of spark discharge have a higher voltage before the discharge. When the two electrodes are close, after the dielectric breakdown between the two electrodes, spark discharge occurs immediately. 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 maintaining for a short period of time (usually 10-7-10-3s) in order to maintain the “cold electrode” characteristic of spark discharge (that is, the heat energy of the channel energy conversion is too late to be transmitted to the depth of the electrode). The channel energy acts on a very small area. The effect of the channel energy can cause the electrode to be corroded locally. The method of sizing materials by using the corrosion phenomenon generated during spark discharge is called EDM. EDM is the spark discharge in the liquid medium in the lower voltage range.
2. Features of EDM:
EDM is a new technology of graphite manufacturer completely different from mechanical processing. With the development of industrial production and the progress of science and technology, new materials with high melting point, high hardness, high strength, high brittleness, high viscosity and high purity are constantly appearing. There are more and more workpieces with various complex structures and special process requirements, which makes traditional machining methods impossible or difficult to process. Therefore, besides further developing and perfecting the mechanical processing method, the graphite manufacturer also strives to find new processing methods. EDM can adapt to the needs of production development, and has shown many excellent performances in applications. Therefore, it has been rapidly developed and increasingly widely used. The characteristics of EDM are as follows:
1. The pulse discharge has high energy density, which is convenient for processing special materials and complex-shaped workpieces that are difficult or impossible to process with ordinary mechanical processing methods. Not affected by the hardness of the material, and not affected by the heat treatment conditions.
2. The duration of pulse discharge is extremely short, the conduction and diffusion range of heat generated during discharge is small, and the range of material affected by heat is small.
3. During processing, the tool electrode does not contact the workpiece material, and the macroscopic force between the two is extremely small. The tool electrode material does not need to be harder than the workpiece material, so the tool electrode is easy to manufacture.
4. The structure of the workpiece can be reformed, the processing technology can be simplified, the service life of the workpiece can be improved, and the labor intensity of the workers can be reduced. Based on the above characteristics, the main uses of EDM are as follows:
1) Manufacture of punching dies, plastic dies, forging dies and die-casting dies.
2) Machining small holes, deformed holes and threaded screw holes on cemented carbide.
3) Cut out parts on sheet metal.
4) Processing narrow slits.
5) Grind flat and round surfaces. 6) Others (such as strengthening the metal surface, taking out the broken tools, perforating the quenched parts, directly processing the parts with complex shapes, etc.).
3. The composition and function of EDM machine tools:
From the situation discussed above, it can be seen that in order to realize the EDM process, the graphite manufacturer machine tool must have three elements, namely: pulse power supply, mechanical parts and automatic control system, working fluid filtration and circulation system. .
The functions of these three elements are briefly discussed below.
1. The voltage applied by the pulse power supply to the discharge gap must be pulsed, otherwise, the discharge will become a continuous arc. The so-called pulse power supply is actually a kind of electrical circuit or device, which can send out a pulse voltage with sufficient energy.
2. The function of the mechanical part and the automatic control system is to maintain a proper discharge gap between the tool electrode and the workpiece, and adjust it online.
3. Working fluid purification and circulation system The function of working fluid is to concentrate energy, strengthen the processing process, and take away the heat and electro-corrosion products generated during discharge. The working fluid system includes the storage cooling, circulation and regulation and protection of the working fluid, filtration and the forced circulation system of the working fluid. The above three elements are sometimes called the three major parts of EDM machine tools. They form the unity of EDM machine tools to meet the requirements of the machining process.