Process is critical in die and mold electrical discharge machining

2021/10/08



The process is crucial when mold electrical discharge machining comes to die and mold electrical discharge machining operations. Why is this important to emphasize, because the right process helps to increase the efficiency of the work and thus the productivity of the process. Take a look next:
 
Why is the process of die and mold electrical discharge machining critical?
 
(1) Proper discharge gap. A reasonable distance between the tool electrode and the workpiece electrode must be maintained, i.e., a proper discharge gap. This gap varies with the processing conditions and is usually about a few microns to a few hundred microns. In the distance range, can meet the pulse voltage constantly penetrate the media, spark discharge, but also can adapt to the media after the spark discharge channel extinguished ionization and discharge the requirements of the etching products. The gap is too large, the inter-pole voltage can not penetrate the inter-pole medium, and therefore can not produce spark discharge. The gap is too small, it is easy to form a short circuit, also can not produce a spark discharge. For this reason, the EDM process must have automatic feeding and adjusting device of the tool electrode, so that it and the workpiece to maintain a certain discharge gap.
 
(2) Sufficient discharge energy. To achieve the purpose of EDM, the local discharge current density must be high enough, usually up to 105A/cm2 - 106A/cm2, so that the local metal can melt or vaporize. After the discharge channel is formed, the pulse voltage does not change much, so the current density of the channel can characterize its energy density. The energy density is large enough to melt or vaporize the material being processed locally, thus forming a corrosion crater on the surface of the material being processed and realizing EDM.
 
(3) Transient one-way pulse discharge. The spark discharge must be instantaneous pulse discharge, the discharge continues for a period of time, need to stop for a period of time, the discharge duration is 10-7-10-3s. Due to the short discharge time, so that the heat generated by the discharge is too late to conduct the diffusion to the inside of the processed material, so that the energy effect is limited to a small range, to maintain the cold pole characteristics of the spark discharge (i.e., the discharge The thermal energy converted from the discharge channel energy is not transmitted to the electrode depth or the inside of the material to be machined), which not only ensures the good machining accuracy and surface quality of the workpiece, but also keeps its intrinsic quality unaffected. And there must be enough stopping time between two successive pulse discharges to avoid arcing, local burn phenomenon. Otherwise, the surface will be damaged like the continuous arc discharge. For this reason, EDM must use pulse power.
 
(4) Insulating liquid medium. EDM must be in a certain insulating performance of the liquid medium (i.e. working fluid), commonly used working fluids are kerosene, deionized water, spark oil, etc.. The liquid medium must have a high insulating strength to facilitate the generation of pulsating spark discharge. At the same time, the liquid medium on the one hand so that the products of galvanic corrosion can be discharged in a timely manner, on the other hand, can cool the workpiece, so that the pulse discharge is carried out smoothly. Only after the discharge of galvanic corrosion products timely discharge outside the discharge channel, the repetitive pulse discharge can be carried out smoothly. In the production practice of EDM, the discharge of electro-etching products is mainly done in two ways: on the one hand, the spark discharge as well as the electro-etching process itself has the inherent characteristic of discharging the etching products, and the rest of the discharge products other than the etching products (such as the vaporization of liquid medium) can also facilitate the above process; on the other hand, some artificial auxiliary process measures must also be used, such as the circulation and filtration of the working fluid. The processing of the use of punching, oil pumping measures.
 
From the physical essence, EDM is a kind of "micro-cutting" process which relies on the ablation of discharge, its macro-process is often very slow, and its micro-process is very short and complex, it is the process of electrodynamic, electromagnetic force, thermodynamic, hydrodynamic and other comprehensive action. China calls it electric discharge machining, the United States, Japan, Britain and other countries called electrical discharge machining, in Russia and other countries called electro-etching processing. Die electrical discharge machining requires some basic conditions to ensure the implementation of the process. Electrical discharge machining is the macroscopic manifestation of the accumulation of numerous microscopic electro-erosion phenomena.