In twentieth Century, copper was widely used as electrode material in edm. At that time, graphite materials would be considered only when large electrodes were produced and the processing of the dies was not high or rough. Some of the early contact with graphite electrode technical staff had a general impression: graphite material dirty, easy to slag, surface effect is not good, processing efficiency is not high.
With the development of high technology, the manufacturing process of graphite materials continue to improve, to meet different EDM graphite materials emerge in an endless stream of market demand, high speed milling of graphite machine came into being, the discharge performance of CNC EDM machine tool also has a comprehensive upgrade. Today, in leading manufacturing Europe, mold enterprises use graphite more than 90% of the electrode material. Graphite, as an electrode material, has been widely used in aerospace, automobile, home appliance and electronic products. This remarkable change has been attributed to the advantages of graphite electrode for high efficiency, high quality processing and many other advantages
The graphite electrode has the characteristics of high current conditions, in addition, in rough set properly under the condition of the carbon steel work pieces produced in the process of removal of carbon particles and the decomposition of working fluid at high temperature to produce the polarity effect, partial eclipse things, carbon particles adhesion forming a protective layer on the surface of the electrode, graphite electrode to ensure minimal loss in rough machining, or even "zero loss". The loss of the main electrode in EDM from rough machining, finish machining conditions while the loss rate is higher, but because of the part machining allowance for not much processing corrosion quantity is less, the total amount of the loss is less. In general, the graphite electrode will lose less than the copper electrode in the roughing of large current, and the loss in finishing may be slightly larger than that of copper electrode, and the electrode loss of the two is quite the same..
Graphite particles directly affect the diameter of EDM roughness, the diameter is small can obtain lower surface roughness. Graphite particle diameter using 5 m a few years ago, only the best surface of EDM to VDI18 (Ra0.8 m), the particle diameter of the graphite material has been able to achieve with within 3 m, the best surface of EDM can reach VDI12 (Ra0.4 m) or finer level however, graphite electrode cannot mirror edm. The low resistivity copper material, compact structure, precision EDM machining to obtain a stable state, but also to stabilize the processing in the more difficult conditions, the surface roughness is less than Ra0.1 m, can mirror edm.
Thus, if the discharge processing pursues extremely fine surface, it is more suitable to use copper material as electrode, which is the main advantage of copper electrode compared with graphite electrode. But the copper electrode at high current conditions, the electrode surface can become rough, even a crack, and the graphite material is no problem in this regard, the surface roughness of VDI26 (Ra2.0 m) cavity processing about 1, the use of graphite electrode can complete the process from coarse to fine. The surface effect of uniform, the surface will not have defects. In addition, because the graphite and copper structure, corrosion surface of the graphite electrode to discharge rules than copper electrode, so in the process of VDI20 and above the same surface roughness, using graphite electrode machining surface of particles more clearly, the surface effect should be better than the copper electrode surface discharge.
