Graphite has the features of high-temperature strength, low thermal expansion coefficient, good workability, and good thermal and electrical conductivity. Therefore, graphite electrodes are widely used in metallurgy, electric furnace, electric discharge machining, and other fields. In terms of EDM, the development of new graphite electrode materials and their processing technology has expanded the application range of EDM and improved its performance.
Compared with the copper cathode, graphite electrode has the advantages of low electrode consumption, fast processing speed, good mechanical processing performance, high processing accuracy, small thermal deformation, lightweight, easy surface treatment, high-temperature resistance, high processing temperature, and electrode bonding.
Although graphite is a very easy-to-cut material, the graphite material used as an EDM electrode must have sufficient strength to avoid damage during operation and EDM processing, and the shape of the electrode (thin wall, small rounded corners, sharp changes), etc. Higher requirements are also placed on the grain size and strength of graphite electrodes. These all lead to the graphite workpiece being easily broken during the machining process, and the tool is easy to wear. Therefore, the important issues of graphite electrode processing are as follows: how to prevent the workpiece from breaking, improve the surface processing quality, and reduce the cost of processing tools.
Generally, conventional turning, milling, and grinding methods can be used to process simple-shaped electrodes. However, in recent years, the requirements for the complexity of electrode geometry have continued to increase. The high processing surface quality and high processing accuracy of high-speed machining have made the high-speed machining of graphite electrodes a hot spot in mold EDM processing. Many manufacturers have launched graphite high-speed machining centers and produced many types of graphite electrodes.
As the high-speed machining of EDM graphite electrodes is still a new process, the machining performance of different graphite materials is also different. Few kinds of literature mention the problems of workpiece collapse, tool wear, and machining strategies in high-speed machining of graphite electrodes.