Electrical discharge machining (EDM) - definition

Electrical Discharge Machining (EDM) is a specialised machining method for the precise removal of material from a workpiece by means of pulses of electrical discharge occurring between electrode and the surface of the workpiece. The process takes place in the presence of a dielectric working medium, usually mineral oil or a synthetic liquid, which acts as an insulator an electrical insulator and coolant, and carries away the resulting erosion products.

EDM makes it possible to machine electrically conductive materials, regardless of their hardness, making the technology particularly suitable for hard-to-machine metals such as carbides, titanium alloys or hardened tool steels. The operating principle is based on microscopic spark discharges that generate local, very high temperatures leading to melting and vaporisation of material particles at the discharge point. Repeated pulses result in a gradual shaping of the surface according to the geometry of the tool electrode.

Others are varieties of EDM, depending on the application and machine design, such as Wire EDM, where the electrode is in the form of a thin wire, and Plunge EDM, where the electrode has a three-dimensional shape and reproduces the desired geometry in the workpiece. This technology is used in the production of injection moulds, dies, precision holes, micro-structured parts and components with complex geometries that cannot be achieved by traditional machining methods.

The EDM process is characterised by very high dimensional accuracy and surface quality, although relatively low material removal rates. It requires the use of advanced numerical control (CNC) and appropriate process parameters, such as voltage, pulse current, frequency and discharge duration, which determine machining efficiency, accuracy and stability.

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