1.A reasonable distance must be maintained between the tool electrode and the workpiece electrode. Within this distance range, it can not only meet the requirements that the pulse voltage continuously breaks down the medium to generate spark discharge, but also meet the requirements of medium deionization and discharge of corrosion products after the spark channel is extinguished. If the distance between the two electrodes is too large, the pulse voltage cannot break through the medium and spark discharge cannot be generated. If the two electrodes are short circuited, there is no pulse energy consumption between the two electrodes and it is impossible to achieve electric corrosion machining.
2.The medium must be filled between the two electrodes. When conducting material EDM dimension machining, the liquid medium (special working fluid or industrial kerosene) is used between the two poles; In the process of material surface strengthening by electric spark, there is a gas medium between the two electrodes.
3. The pulse energy density transmitted between the two electrodes shall be large enough. After the spark channel is formed, the pulse voltage changes little. Therefore, the current density of the channel can characterize the energy density of the channel. Only when the energy density is large enough can the material to be machined be melted or vaporized locally, thus forming a corrosion mark (pit) on the surface of the material to be machined to achieve EDM. Therefore, the channel must generally have a current density of 105-106A/cm2.
The discharge channel must have enough peak current to maintain the channel during the pulse. In general, the peak current of the maintenance channel shall not be less than 2A.
4.The discharge must be a short pulse discharge. The discharge duration is generally 10-7-10-3s. Due to the short discharge time, the heat energy generated during the discharge has no time to diffuse in the material to be processed, thus limiting the energy effect to a small range and maintaining the cold electrode characteristics of spark discharge.
5. The pulse discharge shall be repeated for many times, and the multiple pulse discharges are scattered in time and space.
There are two meanings here: one is that two adjacent pulses at a time do not form a channel at the same point; Second, if the pulse discharge concentrated in a certain area within a certain time range, the pulse discharge should be transferred to another area within another period of time. Only in this way can the phenomenon of carbon deposition be avoided, so as to avoid electric arc and local burns.
6. The erosion products after pulse discharge can be discharged out of the discharge gap in time, so that the repetitive discharge can be carried out smoothly.
In the production practice of EDM, the above process is completed in two ways. On the one hand, the spark discharge and electric corrosion process itself have the inherent characteristics of removing corrosion products; Other discharge products (such as the vaporization of the medium) can also promote the above process.