There is a high voltage between the two electrodes of spark discharge before discharge. When two electrodes are close, the dielectric between them is broken down, and the spark discharge occurs immediately. With the breakdown process, the resistance between the two electrodes drops sharply, and the voltage between the two electrodes also drops sharply.

The spark channel must be extinguished in time after a short time to maintain the "cold pole" characteristics of spark discharge (that is, the heat energy converted from channel energy cannot reach the electrode depth), so that the channel energy can act in a small range. Under the action of channel energy, the electrode will be partially corroded. ?

The method of sizing materials by using the corrosion phenomenon produced by spark discharge is called EDM. EDM is a kind of spark discharge in liquid medium in low voltage range.

Extended data

According to the form of tool electrode and the characteristics of relative motion between tool electrode and workpiece, EDM methods can be divided into five categories:

1, using the electrode of the forming tool to perform simple feed movement relative to the workpiece;

2. With the metal wire moving in the axial direction as the tool electrode, the workpiece moves along the track according to the required shape and size, and the conductive material is cut by WEDM;

3. Use metal wire or special-shaped conductive grinding wheel as tool electrode to carry out small hole grinding or electric spark grinding for special-shaped grinding;

4, used for machining thread ring gauges, thread plug gauges, gears and other EDM yokes;

5. Small hole processing, carving, surface alloying, surface strengthening and other processing.

Baidu encyclopedia -EDM