What is wire EDM?
Release date:
2022-04-13
What is medium-speed wire EDM? The medium-speed wire-cutting machine (medium-speed wire electrical discharge machining, MS-WEDM) belongs to the category of reciprocating high-speed wire EDM machines. It is a type of high-speed reciprocating wire EDM, commonly referred to as “wire cutting.” It should be noted that the term “medium-speed” does not refer to an intermediate speed between high and low; rather, it describes a composite wire‑cutting process. Specifically, the wire‑feeding principle involves using high‑speed wire feed (8–12 m/s) during rough machining and low‑speed wire feed (1–3 m/s) during finish machining. This approach ensures relatively stable workpiece operation with reduced vibration, while multiple passes help minimize errors caused by material deformation and wear of the molybdenum wire.
What is medium‑speed wire EDM? The medium‑speed wire EDM machine (medium‑speed wire electrical discharge machining, MS‑WEDM) is a reciprocating high‑speed wire EDM, classified as a high‑speed reciprocating wire EDM and commonly referred to as “wire cutting.”
It is pointed out that the so‑called “medium‑speed wire EDM” does not refer to a specific wire‑feed speed between high and low speeds, but rather to a hybrid wire‑cutting machine. In this type of machine, the wire‑feed principle involves using a high feed rate (8–12 m/s) during rough machining and a low feed rate (1–3 m/s) during finish machining. This approach ensures relatively stable workpiece operation with reduced vibration, and by performing multiple cuts, it minimizes errors caused by material deformation and molybdenum‑wire wear, thereby improving overall machining quality. As a result, the machining quality falls somewhere between that achieved with high‑speed and low‑speed wire‑feed machines.
Thus, it can be said that what users refer to as “online” actually involves adopting certain low‑speed wire EDM techniques on reciprocating wire EDM machines, enabling streak‑free cutting and multi‑pass machining. Practice has shown that the primary objective of multi‑pass cutting is high‑speed, stable material removal, for which peak current and long pulse width can be selected to achieve elevated cutting speeds. The second cutting pass focuses on finish machining to ensure dimensional accuracy; with medium‑sized parameters, the surface roughness after the second pass typically falls within the range of 1.4–1.7 μm. The third, fourth, or subsequent passes—currently, wire‑feed control software can support up to seven passes—are dedicated to polishing and burnishing. Pulse width (now adjustable up to 1 μs) can be fine‑tuned, while peak current is varied according to surface‑quality requirements. The wire‑feeding strategy resembles that of the second pass, as a low wire‑feed speed can be employed to maintain tight tolerances.
During the wire EDM process, special attention must be paid to managing deformation during multiple cutting passes. As the workpiece is machined in‑line, the combined effects of residual internal stresses and thermal stresses generated by electrical discharge machining can induce random, irregular distortions, leading to uneven tool‑to‑workpiece clearance and compromising machining quality and accuracy. Therefore, it is essential to allocate appropriate machining allowances for different materials, allowing the workpiece to fully relieve its internal stresses and undergo complete distortion. This ensures that subsequent multiple cutting operations will have sufficient material remaining for fine finishing, thereby guaranteeing the final dimensions of the part.
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