1. What is EDM?
Have you ever seen sparks to weld steel frames in construction sites of buildings?
And sparks sometimes come out when you insert wall sockets.
Sparks emitted towards metal in the air melt it in the high temperature. Large sparks make large melt, and small sparks make small melt.
What happens if we make a spark toward a metal in a liquid? The spark melts the metal. When the spark stops, the melted part in the liquid is cooled rapidly and scatters intensely. The remaining portion is depressed like a hole, and it looks like a crater of the moon.
EDM is a processing method using this phenomenon.
It is a machining method to carve metals by hitting sparks intermittently and repeating metal dissolution, cooling, scattering.
Click on the image to see an animated image of EDM.
The surface by discharge machining (100 x)
(Machined surface is formed by a myriad of microscopic craters.)