Principle and Conditions of Wire EDM Machining

Release date:

2022-12-29

　　 Wire EDM is also a type of wire-cutting machine tool. Its basic operating principle involves using a continuously moving molybdenum wire—referred to as an electrode wire—as the electrode; pulsed electrical discharges generate sparks that remove material from the workpiece, thereby achieving the desired shape. Because the quality of the machined parts falls between that of conventional and high‑speed wire EDM, it is termed “medium‑speed wire EDM.” More precisely, medium‑speed wire EDM represents an upgraded version of high‑speed wire EDM, allowing for repeated cutting operations.

　　However, the wire‑cutting speed in this process is not lower than that of fast‑wire cutting; rather, it exceeds it. Only by reducing the cutting speed during multiple passes can the desired cutting results be achieved. Average efficiency—not peak efficiency—is used for calculations, and the machining quality often deteriorates as the wire feed rate decreases. The wire‑feed speed is automatically controlled by the system and can be adjusted to meet the specific needs of the enterprise.

　　 It is primarily used for machining complex shapes and small workpieces, such as punch dies and cavity molds. It has evolved through the continuous integration of electrical discharge machining and perforation‑forming processes. Not only has it expanded the applications of electrical discharge machining, but in certain areas it has even begun to replace traditional electrical discharge drilling and forming techniques. Wire EDM machines account for more than half of all electrical discharge machining equipment.

　　 Its basic operating principle is as follows: the wire electrode on the wire‑winding spool rotates in one direction at a specified speed, while the workpiece mounted on the machine tool’s worktable moves along a pre‑programmed trajectory, enabling wire‑EDM machining. One terminal of the pulse power supply is connected to the workpiece, and the other to the wire electrode. A constant discharge gap is maintained between the workpiece and the wire, and a dielectric fluid is continuously sprayed.

　　The spark erosion between electrode materials exhibits a certain gap, allowing continuous use of pulsed wire EDM to machine workpieces into the desired shapes and dimensions. In the field of wire‑EDM technology, it should be noted that although the development of “wire” EDM machines has demonstrably improved product quality compared with fast‑feed wire EDM, they still do not fall within the category of medium‑feed wire EDM machines. Moreover, their cutting accuracy and surface finish may still differ significantly from those of low‑speed wire EDM machines, and further enhancements are needed in terms of stability, precision, and surface quality.

　　“Online wire EDM machines” are characterized by their simple structure, low cost, and minimal consumable usage, leaving room for market viability. The applicable standards remain those specific to high-speed online wire EDM machines, which manufacturers should emphasize in their marketing communications. We must adhere to factual accuracy. The medium‑speed wire EDM process can operate normally. Medium‑speed wire EDM technology indicates that the following conditions must be met:

　　 1. In wire EDM, a certain gap must be maintained between the wire and the workpiece surface; the gap width depends on process parameters such as the operating voltage and the material removal rate.

　　 2. To facilitate the generation of pulsed spark discharges, the formation of a liquid dielectric, and the removal of corrosion products from the gap and the cooling electrodes, high dielectric strength is required. A certain gap must be maintained between the wire EDM electrode and the workpiece surface; if the gap is too large, the voltage between the electrodes cannot penetrate the dielectric medium, and no spark discharge will occur. Conversely, if the gap is too small, a short circuit may easily form, also preventing spark discharge.

Tags:

The Development of Wire EDM

Methods for processing wire EDM cutting

The Development of Wire EDM

Methods for processing wire EDM cutting