Electric Discharge Machining (EDM) is a manufacturing process whereby a desired shape is obtained using electrical discharges. Material is removed from the workpiece by a series of rapidly recurring current discharges between two electrodes, separated by a dielectric liquid and subject to an electric voltage. One of the electrodes is called the tool-electrode, or simply the ‘tool’ or ‘electrode’, while the other is called the workpiece-electrode, or ‘workpiece’.
Electrical Discharge Machining is a machining method primarily used for hard metals or those that would be very difficult to machine with traditional techniques. EDM typically works with materials that are electrically conductive, although methods for machining insulating ceramics with EDM have also been proposed. EDM can cut intricate contours or cavities in pre-hardened steel without the need for heat treatment to soften and re-harden them. This method can be used with any other metal or metal alloy such as titanium, hastelloy, kovar, and inconel. Also, applications of this process to shape polycrystalline diamond tools have been reported.
EDM is often included in the ‘non-traditional’ or ‘non-conventional’ group of machining methods and opposite to the ‘conventional’ group (turning, milling, grinding, drilling and any other process whose material removal mechanism is essentially based on mechanical forces).
Advantages include:
Complex shapes that would otherwise be difficult to produce with conventional cutting tools
Extremely hard material to very close tolerances
Very small work pieces where conventional cutting tools may damage the part from excess cutting tool pressure
There is no direct contact between tool and work piece. Therefore delicate sections and weak materials can be machined without any distortion
A good surface finish can be obtained
Very fine holes can be easily drilled
