EDM (electric discharge machining) is a process which removes metal by vaporizing it with a spark. Anyone who has ever dropped a wrench across a car battery has witnessed a very crude form of EDM. The modern EDM process uses high frequencies, sometimes creating hundreds of thousands of tiny sparks per second. A servo motor changes the feed rate of the electrode to keep the voltage constant and a dielectric fluid serves the purposes of acting as a dielectric barrier to allow the charge to build up, a coolant to prevent the electrode from getting hot, and removing the vaporized metal particles. Early models in the 50's like the ELOX M200 were mainly used to remove broken taps and drills. As they became more sophisticated and larger, they were used to burn dies, and were commonly called die sinkers - many people refer today to vertical EDM's as sinkers because of this. Also called "ram" and "conventional" EDM, this type of EDM employs an electrode cut to the shape of the desired cavity. The advantage of the conventional EDM is that it can do 3 dimensional cuts. The disadvantage compared to wire EDM is that it requires an electrode and is relatively slow. When preparing jobs for conventional EDM, it is best to remove as much material as practical conventionally as the EDM process is slow. In wire EDM, the opposite is true. Conventional EDM's generally use specialized oil as a dielectric, although there are a few that use water.
We have 4 CNC EDM's including a Sodick AG60 with linear motors purchased in September of 2012, and a Sodick AD35L purchased in 2015.