Graphite is the most preferred electrode material for sinker EDM applications. It has been over half a century since graphite was introduced to the EDM industry. But even with the modern advancements in machining technology, graphite electrodes remain an integral part of the industry. It is cost-effective and provides excellent results. It is similar to diamond tools that have also withstand the test of time and the arrival of new technology by being easy, affordable to use and providing the needed results.
Graphite is made using carbon powder which is derived from petroleum. The carbon powder is mixed with a petroleum-based binder. The mixture is then compacted to create a block. The way the graphite is compacted greatly influences its properties. In the early days, graphite was made by compressing the mixture in only one direction. This resulted to the formation of grains. These grains affected the structural strength of the formed graphite and other properties like resistance to wear and machinability.
The needs of the aerospace industry resulted a newer method of compacting the carbon-binder mixture. The isostatic pressing of the mixture created blocks with uniform properties all throughout. This compacting process is used to produce the modern high-quality graphite which is used for sinker EDM electrodes. The block then undergoes several heat treatments that converts carbon to graphite. The fineness of the carbon powder determines that finishing quality of the EDM.
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