Strategy of High Speed Machining of Graphite Electrode and Principle of Optimizing Selection of Machining Parameters

2019-01-15 點擊量：3893

 

Graphite has high high temperature strength, low thermal expansion coefficient, good machinability and good thermal and electrical conductivity, so graphite electrodes are widely used in metallurgy, electric furnace, EDM and other fields. In the field of EDM, the development of new graphite electrode materials and processing technology has expanded the application scope of EDM and improved its performance.
Compared with copper electrodes, graphite electrodes have the advantages of low consumption of electrodes, fast processing speed, good machinability, high processing accuracy, small thermal deformation, light weight, easy surface treatment, high temperature resistance, high processing temperature and bondable electrodes.
Although graphite is a very easy-to-cut material, graphite materials used as EDM electrodes must have sufficient strength to avoid being destroyed during operation and EDM processing. At the same time, the shape of the electrodes (thin wall, small fillet, sharp change) also puts forward higher requirements for the grain size and strength of graphite electrodes, which leads to the easy collapse of graphite workpieces in the process of processing. Tools wear easily. Therefore, how to prevent the workpiece from breaking up, improve the surface processing quality and reduce the cost of cutting tools has become an important issue in graphite electrode processing.
_Conventional turning, milling and grinding methods are usually used to meet the needs of processing simple shape electrodes, but in recent years, the requirements for the complexity of electrode geometry continue to increase. High-speed machining surface quality and high processing accuracy make the high-speed processing of graphite electrodes become a hot spot in EDM processing of dies. Many manufacturers have introduced graphite high-speed machining centers. For example, Makino SNC64 NC high-speed graphite milling machine, RFM series machine tools, etc., spindle speed is usually 10000-60000 r/min, feed speed can reach more than 60 m/min, processing wall thickness is less than 1 mm, minimum fillet radius is less than 0.2 mm.
Owing to the fact that EDM graphite electrode high-speed machining is still a new technology, the processing performance of different graphite materials is also different. There are few references on workpiece breakage, tool wear and processing strategy in high-speed machining of graphite electrode in China. This paper introduces the research achievements of Japan and Germany in the mechanical processing of high performance graphite electrode materials, including the basic theories of cutting mechanism, cutting temperature, tool wear and chip treatment of graphite electrode materials, as well as the strategy of high speed machining of graphite electrode and the selection of processing parameters.