An EDM machine, or electrical discharge machine, is a device that cuts metal via the use of spark erosion. A small spark actually vaporizes the metal in a highly controlled situation. The process is known as burning, die sinking, wire erosion, spark erosion, or spark machining.

EDM is a fairly new method of cutting. The EDM process was invented in the 1940's by Russian scientists. The first machines were produced by AGIE in 1969, a Swiss company, which worked together with Texas A&M University to investigate the thermal processes behind EDM. The computer-controlled EDM was invented in Japan by Makino in 1980.

EDM is often included in the non-conventional group of machining methods similar to water jet or laser cutting (Conventional methods include grinding, drilling, and milling). It is often used to cut hard metals, even pre-hardened steel, and materials are usually electrically conductive. Ceramics have been proposed as a material that can be cut with EDS, but they have not widely caught on.

There are two main types of EDM machine - the Sinker EDM and the Wire EDM. The Sinker is sometimes known as the cavity type or ram-type EDM. The Sinker takes its name from the fact that the electrode and work piece are submerged in a liquid, which is usually a dielectric oil, and then the electrode slowly sinks into the part as the metal of the part is eroded in the shape of the electrode. When electrical current is run through the machine, a spark jumps from the electrode to the work piece vaporizing the metal at a rate of several hundred thousand sparks per second. The rate of metal removal and the quality of the surface finish achieved can be controlled by various machine parameters.

In wire electrical discharge machining, also known as wire-cut EDM, a thin metal wire is fed through the work piece, which is typically, but not always submerged. Brass is the most commonly used type of wire. The wire is held between diamond guides, and if the work piece is submerged, water is most commonly used. The water helps flush away the cutting debris- this is important because wire EDM is often used to cut very intricate parts, and machine calibration is very sensitive. Tiny bits of metal in the water can interfere with the process by filling the gap between the part and the wire eliminating the spark, so filtering is critical for submerged wire EDM machines.

One of the advantages of EDM over traditional parts manufacture is that complex shapes are comparatively easier to create. EDMs can be used to machine a wide variety of materials with closer tolerances than conventional machining. Very small delicate pieces can be created without damage due to cutting pressure, and aforementioned cost-effectiveness of small volumes.

EDM does have some disadvantages. Material is removed much more slowly than conventional machining methods, which leads to longer production times. Also, with ram-type EDMs, the production of sharp corners on the work piece is difficult, due to electrode wear.