From the beginning of 21 century, more and more customers select graphite as electrode for EDM; in Europe, above 90% of electrode material is graphite.
Copper, compared with graphite, have lost all its advantages.
The Advantages of Graphite:
1. Fast processing speed: generally, the machinning speed of graphite is 2 – 5 times than copper, and discharge rate is 2 – 3 times than copper.
2. Graphite is not easy to deform: graphite has obvious advantage than copper in processing tiny electrode. The soften piont of copper is about 1000 degree, which is easily deform when heated; submilation temperature of graphite is 3650 degree, thermal expansion index is only 1/30 of copper.
3. Graphite is lighter than copper: density of graphite is 1/5 of copper, when large scale electrode is discharging, it will reduce the burden of EDM machine tool effectively; more suitable to apply in large mould.
4. Less electrode consumption: there is C atom in EDM oil, when discharging, the C atom in EDM oil was disintergrated by high temperature, form protection film on the surface of graphite electrode, compensate the consumption of graphite electrode.
5. No rag on surface of graphite electrode after machining, which will save lot of time.
6. Graphite is more easy to grind and polish.
7. Lower material cost, stable price: due to price rise of graphite recent years, price of isostatic graphite is lower than copper nowadays; under same volume, price of Toyo Tanso isostatic graphite is lower than copper by 30% – 60%, and price is more stable.
According to these incomparable advantages, graphite has gradully take place of copper to become preferred material as EDM electrode.