The strategy of high speed machining of graphite electrode and the selection principle of machining parameters
Graphite has high high temperature strength, low thermal expansion coefficient, good machinability and good thermal and electrical conductivity, so graphite electrode is widely used in metallurgy, electric furnace, edm and other fields. In the aspect of edm, the development of new graphite electrode materials and its machining technology has extended the application scope of edm and improved its performance.
Compared with copper electrode, graphite electrode has the advantages of small consumption of electrode, fast processing speed, good mechanical processing performance, high processing accuracy, small thermal deformation, light weight, easy surface treatment, high temperature resistance, high processing temperature, electrode adhesion and so on.
Although graphite is a kind of very easy cutting material, but as a result of used for EDM electrode graphite materials must have sufficient strength to avoid damage in the process of operation and EDM machining, the electrode shape, thin wall and small rounded corners and sharp change) and also on the grain size and strength of graphite electrode put forward higher requirements, resulting in graphite in the process of machining workpiece easily broken, tool wear and tear. Therefore, how to prevent the workpiece from breaking, improve the surface processing quality and reduce the cost of cutting tools has become an important problem in graphite electrode processing.
The conventional turning, milling and grinding methods can meet the needs of machining simple shaped electrode, but in recent years, the requirements of electrode geometry complexity keep increasing. The high machining surface quality and high machining precision of high speed machining make the high speed machining of graphite electrode has become a hot spot in the EDM machining of mold. Many manufacturers have launched graphite high speed machining center. For example, Makino SNC64 CNC high-speed graphite milling machine, R? :ders RFM series machine tools, the spindle speed is usually in 10000 ~ 60000r/min, feed speed can reach more than 60m/min, processing wall thickness is less than 1mm, the minimum radius of the circular Angle is less than 0.2mm.
Because EDM graphite electrode high-speed machining is still a new process, the processing properties of different graphite materials are not the same, for the graphite electrode high-speed machining workpiece breakage, tool wear, processing strategy and other issues, few domestic literature mention. This paper introduces the research achievements of Japan and Germany in the mechanical processing of high-performance graphite electrode materials, including the cutting mechanism, cutting temperature, tool wear, chip processing and other basic theories of graphite electrode materials, as well as the high-speed processing strategy of graphite electrode and the selection of processing parameters.