Electric-discharge machining is a reproducing forming process, which uses the material removing effect of short, successive electric discharges in a dielectric fluid. Hydrocarbons are the standard dielectric, although water-based media containing dissolved organic compounds may be used. The tool electrode is generally produced as the shaping electrode and is hobbed into workpiece.
With each consecutive impulse, a low volume of material of the workpiece and the electrode is heated up to the melting or evaporation temperature and blasted from the working area by electrical and mechanical forces. Through judicious selection of the process parameters, far greater removal can be made to occur at the workpiece than at the tool, allowing the process to be economically viable. The relative abrasion, i.e. removal at the tool in relation to removal at the workpiece, can be reduce to values below 0.1%.