The EDM is derived from Electrical Discharge Machining.
The EDM process as we know it today started in 1770 with the observations of Joseph Preistly. He noticed that electrical discharges had removed material from electrodes used in his experiments. This is also known as electro-discharge erosion.

Later on in the 1940’s Soviet researchers developed a machining process that formed the foundation for modern day EDM.

Electric Discharge Machining
The basic EDM process is an electrical spark that is created between an electrode and a work piece. The spark is visible evidence of the electro-discharge. This electric spark produces intense heat with temperatures reaching 8000 to 12000 degrees Celsius, melting almost anything.

The spark is very carefully controlled and localized so that it only affects the surface of the material. The EDM process usually does not affect the heat treat below the surface. With wire EDM the spark always takes place in the dielectric of deionized water. The conductivity of the water is carefully controlled making an excellent environment for the EDM process. The water acts as a coolant and flushes away the eroded metal particles.