Electrical discharge machining (EDM) is a high precision process of removing material via blasts of electrical current. It is capable of achieving dimensional accuracy within ±.0001”.
An electrode (e.g. carbon) is fabricated to the desired final shape. It is then plunged into the workpiece in a series of cycles under high current.
An electrified wire is used to cut metal like wire is on cheese. Very intricate parts can be created with out the need for a custom tool.
EDM is a common, yet expensive process sometimes necessary in mold making. Some geometries cannot be created by traditional machining, so EDM is employed.