Graphite Electrode for Electrical Discharge Machining
Electrical Discharge Machining
Graphite is the most commonly used electrode material for EDM. Its high resistance to thermal shock and the ability to maintain geometrical integrity during discharge make it the ideal material for the production of mould and die components.
The most important factor in choosing a graphite material is particle size. Particle size has a direct impact on metal removal rate, surface finish and electrode wear.
Ultrafine grades with small particles and pores tend to produce better finishes than coarser grades with larger pore sizes. This can be achieved with the proper EDM machine parameters and graphite selection.
Superfine grades with particles ranging from 6 to 10 microns are usually required for machining cavities with large detail. They often require the use of a powder additive and are less effective for machining smaller holes or cavities.
Fine-grain graphites with particles ranging from 11 to 20 microns are the most common type of electrode material and can provide a very fine surface finish with standard EDM technology without a powder additive. They can also provide near mirror-like finishes with the addition of a powder additive.
Unlike copper, graphite tends to wear slower with the increasing intensity of current. This is particularly true in the roughing stages when the electrode is working with a high amperage and long on times.
