High speed 3D milling by dry EDM

This paper describes the high speed EDM milling of 3D cavities using gas as the working fluid. In this new process, the molten workpiece material is removed and flushed out of the working gap with the help of high-pressure gas flow. The advantages of this technique are the remarkably small tool electrode wear and the significantly high material removal rate especially when oxygen gas is used due to the extremely strong oxidation of steel workpieces. Experiments showed that the material removal rate increases dramatically when the discharge power density on the working surface exceeds a certain threshold due to thermally activated chemical reaction between the gas and workpiece material. The maximum removal rate obtained was almost equal to that of high speed milling of quenched steel by a milling machine. The machining accuracy was considerably better when the gas was sucked through the pipe electrode than jetted.