EDM (Electrical Discharge Machining)

     Electrical Discharge Machining (EDM) is a controlled metal-removal process that is used to remove metal by means of electric spark erosion. In this process an electric spark is used as the cutting tool to cut (erode) the workpiece to produce the finished part to the desired shape.

Electrical Discharge Machining Working Scheme

     Due to electrical discharge, there is a very big temperature (8000÷12000 K) between electrodes. Electrodynamical forces and large point internal stresses, caused by temperature difference, cause the erosion. The discharge time is extremely short, so heat applied is very short and shallow.
     Working principles of electro-discharge machining are very simple. The workpiece and the electrode are immersed in a dielectric fluid such as oil or deionized water. The electrode and workpiece are separated by a small gap and voltage is applied. When there is enough voltage, the dielectric breaks down. A spark jumps the gap, striking the workpiece and vaporizing part of the material. The high speed electrons then impinge on the job and ions on the tool. The kinetic energy of the electrons and ions on impact with the surface of the job and tool respectively would be converted into thermal energy or heat flux. Such intense localised heat flux leads to extreme instantaneous confined rise in temperature which would be in excess of 10,000 K. The intense heat also melts a small portion of the material. The current then is pulsed off, and the dielectric flows into the area carrying away most of the melted material in the form of small chips.