This is a very economical process for cutting through-hole of arbitrary geometry in workpiece. The wall of the openings may be inclined to the plate surface. Thanks to the considerable efficiency of this process, some cavities are increasingly being cut directly into mold plates. The metal is removed by an electrical discharge without contact or mechanical action between the workpiece and a thin wire electrode. The electrode is numerically controlled and moved through the metal like a jig or band saw. Deionized water is the dielectric fluid, and is fed to the cutting area through coaxial nozzles. It is subsequently cleaned and regenerated in separate equipment.

Modern equipment has 5-axis CNC controls with high-precision positioning systems. Standard equipment can handle complicated opening and difficult contours with cutting heights up to 600mm. the width of the gap depends on the diameter of the wire, a diameter of 0.03mm to 0.3mm. the wire is constantly replaced by winding from a reel. Abrasion and tension would otherwise cause the wire to break. Furthermore, the cuts would not be accurate as the wire diameter would become progressively shorter.