The main principle of wire EDM cutting is the application of electrical discharges (sparks) on a part, that are generated as a result of pulsating current passing between a charged wire and the workpiece (electrodes) at a frequency ranging from 50 hertz to hundreds of kilohertz. The workpiece and wire are separated by a dielectric liquid. As result of the electrical discharges, microparticles are removed from the wire and workpiece and carried from the spark gap by the dielectrics stream. Moreover, the dielectric is a decomposition catalyst, under the high temperature of a discharge, the dielectric liquid is gasified around the spark gap and these vapour's that cannot immediately escape cause a complementary 'micro explosion'.
From a physical chemistry point of view, the high thermal temperatures destroy the crystal lattice of the workpiece, and the metal ions then lose contact with surface. When viewed, this process looks like the charged wire is eroding the metal and slowly sinks into the workpiece. The brass wire creates an opening in the workpiece which creates the required contour.
Wire EDM machining is used when traditional machining is difficult or uneconomic because of wastage or difficult to machine (hardened) metals.
CNC Wire EDM machines are used for cutting sheet metals by electro-erosion. Machines are available with 2 or 4 axes that can cut curvilinear contours with either vertical or tapered sides.
Operations included are:
- 2D EDM 2D Contouring
- 4D EDM 4D Contouring