While many forms of erosion are considered to be detrimental, wire erosion is actually very different. Wire erosion, or more properly — electric discharge machining (EDM) — refers to the machine process where electrical sparks are used to cut metal. In some cases, cutting, milling, or grinding (among other processes) is sufficient to cut, resize, or shape a piece of metal. In other cases, for example when working with hard metals such as hardened steel or carbide, EDM is the best or possibly only way to get the job done.
The process of wire erosion involves an electrode and a workpiece. The electrode, commonly referred to as a tool, conducts electricity from the power supply that it is connected to. The electricity travels through the electrode and creates sparks at the end of the electrode. These sparks essentially do the work of cutting or otherwise changing the shape of the metal piece, commonly referred to as a workpiece. The electrode is typically moved in a vertical direction while the workpiece is moved in a horizontal position, if needed. All of this reshaping is performed in liquid; the purpose of this liquid is two-fold — to conduct electricity and flush the resulting metallic dust away from the work area. Since it's the sparks that do all of the work, some people refer to this process as spark erosion.
The electrode or tool in wire erosion can come in a variety of shapes, but most commonly, it's a thin wire. It can also be a bar of different shapes, like a circle, star, or rectangle. The sparks that come off the end of the electrode don't modify the workpiece alone. The electrodes also get worn after long use. Therefore in the case of a wire-shaped electrode, the wire is fed between two spools so that new wire is doing the cutting.
The workpiece in wire erosion is typically a type of metal that can't be cut by more common and easier methods. As a result, hardened steel or carbide — materials that can't be cut or drilled, for example, by traditional methods — may require wire eroding in order to be cut. The shape of the workpiece is usually a block of metal.
Wire eroding is commonly used in manufacturing environments that work with metals. The process is used in a whole host of industries but it's primarily used in tooling — the making of tools and machines.