Carbon deposition: abnormal Electric Discharge Machine. In the discharge process of Electric Discharge Machine, when the gap between the electrode and the workpiece is reduced to a certain distance, the on time applied on the electrode and the workpiece breaks down the dielectric (spark oil) to form a discharge channel, and then the spark starts to discharge. A large amount of heat energy is instantaneously concentrated in the discharge channel, and the instantaneous temperature can be as high as 10000 ℃. The high temperature makes the surface of the workpiece melt and gasify. And the explosive splashing into the processing fluid, quickly solidified into discharge slag, is taken away by the flowing working fluid. At this time, a small pit is left on the surface of the workpiece, and then the discharge enters the off ftime period. The discharge stops for a short time, and the insulation between the electrode and the workpiece is restored. However, when the metal particles between the electrode and the workpiece are not completely taken away by the processing fluid, the ionization cannot be completely eliminated. When the next on time comes, it will form a short circuit. At this moment, the high temperature will create a bump on the surface of the workpiece and form carbon deposition. Carbon deposition should be avoided in EDM, especially in precision die machining.
