EDM or electrical discharge machining is the use of an electrical discharge to remove pieces of the workpiece in a desired pattern or shape. This is done through two electrodes, one being the tool and the other being the workpiece, that is separated by a dielectric liquid and never make direct contact with each other.
With wire EDM the tool electrode is a piece of wire. This is typically copper or brass and can be as small as 0.1mm in diameter to as large as 0.3mm for most applications. The wire electrode and the workpiece, which will never make direct contact, keep this spark in a very specific focus area. The temperature can reach up to 12,000 degrees Celsius, allowing even hardened steel to melt.
The Process
The use of wire EDM will require a hole drilled into the workpiece that is large enough to allow the wire to be inserted through the hole without contact. It is also possible to start from the edge; this will depend on the final shape required. Water, the dielectric liquid, is forced through the gap between the two, removing material and also providing a cooling effect and eliminate heating of the surrounding metal that may change the physical properties around the cut area.
The wire can be held perpendicular to the workpiece, creating a straight edge. It is also possible to precisely incline the wire to create a beveled edge or a taper. As this is done with great precision, it is possible to vary the shape and edge profile for different projects.
With most wire EDM processes, the wire will be spooled during the process, constantly moving any wired with surface erosion out of the cutting area to prevent the wire from breaking.
Skimming, which is a secondary application of the process, can be used to smooth the surface and provide the precise, tight tolerances required for many components used in a variety of industries.
