The Wire Electrical Discharge Machining Process

The wire EDM machine was first discovered in the 1960s to fulfil the purpose of producing tools from hardened steel. The first available numeric controlled (NC) wire-cut EDM machine was manufactured in 1967. Wire electrical discharge machining (WEDM) (Fig.3) comes under the non-conventional machining process that uses electric power to cut any conductive material precisely and accurately using a thin, electrically charged wire serve as an electrode. During the process, the wire carries one side of the electrical charge and the workpiece carries the other. When the wire gets close to the workpiece, the attraction of electrical charges generates a controlled spark, melting and vaporizing microscopic particles form the workpiece material. The

In many cases the whole part is submerged into the fluid and high pressure nozzles are used to remove the material from the surrounding of the wire during the machining process. The fluid also acts as a non-conductive barrier and resists the flow of current between the wire and the workpiece. As the wire gets close to the surface of the workpiece, the intensity of the electric field overcomes the strength of the dielectric fluid and dielectric breakdown occurs, allowing current to flow between the wire and the workpiece, resulting in an electrical

In other words we can say that the white layer (Fig. 4) is the layer that has been heated to the point of a molten state, but not quite hot enough to be ejected into the gap and be flushed away. This layer has different metallurgical and structural characteristics compare to the base material as it is formed by the unexpelled molten metal being rapidly cooled by the dielectric fluid during the flushing process and resolidifying in the cavity. The carbon percentage of the white layer is increased due to the heat treatment or carbon uptake during the process. This carbon enrichment occurs when the hydrocarbons of the electrode and dielectric fluid break down during the EDM process and impenetrate into the white layer while the material is essentially in its molten