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.
- Fast processing speed: generally, the machinning speed of graphite is 2 – 5 times than copper, and discharge rate is 2 – 3 times than copper.
- 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.
- 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.
- 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.
- No rag on surface of graphite electrode after machining, which will save lot of time.
- Graphite is more easy to grind and polish.
- 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.