Rapid Wire EDM Machining
In the world of precision manufacturing, wire electrical discharge machining (WEDM) is like a silent master sculptor—using electricity as its blade and sparks as its brush to carve out microscopic precision in the realm of metal. Among its techniques, medium-speed wire EDM stands out with unique advantages, earning its reputation as a dominant choice across a wide range of manufacturing applications. Today, let us delve into the essence of this technology and explore its practical value.
Introduction to Wire EDM
Definition of Wire Electrical Discharge Machining (Wire EDM):
Wire EDM is a non-traditional machining process that uses a continuously moving, electrically charged thin wire as an electrode to cut or shape electrically conductive materials. The process removes material through controlled electrical discharges (sparks) between the wire and the workpiece, without direct mechanical contact.
Basic Principle of Wire EDM
Wire electrical discharge machining (Wire EDM) can easily cut through several centimeters of steel plate with just a single thin wire, splitting it within seconds. But how can a wire as thin as a human hair cut through solid metal? The answer lies in its principle of operation.
During cutting, the sparks that flash are actually electrical discharges. In this process, the workpiece and the wire electrode are connected to the positive and negative poles of a high-frequency pulsed power supply. When discharges occur, the temperature at the center of the discharge channel can exceed 10,000 °C, which melts or vaporizes the metal of the workpiece. At the same time, part of the dielectric fluid vaporizes, causing rapid thermal expansion and localized micro-explosions. These explosions, along with the flushing action of the dielectric fluid, expel the molten and vaporized metal debris away from the cutting zone, thereby achieving material removal by electrical erosion.
In Wire EDM, brass wire is most commonly used as the electrode, though tungsten and molybdenum wires are also applied in certain cases. However, Wire EDM can only process electrically conductive materials; non-conductive materials such as plastics or ceramics cannot be machined with this method.
Classification of Wire EDM Machines:
Wire Electrical Discharge Machining (WEDM) machines are generally divided into two categories according to the wire travel mode:
• Low-speed unidirectional wire EDM machines, commonly referred to as low-speed wire-cutting machines. In these machines, the electrode wire moves at a relatively low speed in a single direction, typically below 0.2 m/s. Such machines are mainly produced and used abroad.
• High-speed reciprocating wire EDM machines, commonly referred to as high-speed wire-cutting machines. In these machines, the electrode wire moves at a relatively high speed with periodic reciprocation, usually between 8–10 m/s. Featuring a simple structure and high cost-performance ratio, this type of machine is mainly produced and used in China, and represents an original wire EDM machining model developed in China.
Medium-Speed Wire EDM Technology:
Medium-speed wire electrical discharge machining (WEDM) technology is developed on the basis of high-speed reciprocating wire EDM machines, enabling multi-pass cutting functions. It integrates the cutting process of low-speed wire EDM into high-speed wire EDM, thereby achieving requirements such as multiple cuts and streak-free cutting.Medium-speed WEDM combines the advantages of both low-speed and high-speed wire cutting when machining workpieces. While maintaining relatively high cutting efficiency, it enhances accuracy to within ±0.005 mm through multiple cuts and improves surface roughness to Ra < 0.8 μm.
A medium-speed wire EDM machine can perform up to seven cuts. The basic principles of part machining are generally divided into rough machining → semi-finish machining → finish machining.Rough machining: The main objective is to remove excess material as quickly as possible. This is typically carried out with high-speed wire feeding at 8–13 mm/s, using high current and large pulse width for heavy cutting.Secondary cutting: The purpose is fine adjustment to ensure dimensional accuracy. This is achieved with low-speed wire feeding, usually 1–3 mm/s.Final cutting: The main goal is grinding and polishing to improve the surface finish.Through multiple cutting passes, medium-speed WEDM can achieve high machining accuracy and surface quality.During wire EDM machining, the current density in the discharge zone is approximately 10,000 A/mm², and the temperature reaches about 10,000–12,000 °C. Under the combined effect of instantaneous high temperature from spark discharge and rapid cooling by the working fluid, the surface layer of the metal material is divided into a recast (melted–solidified) layer and a heat-affected layer. The recast layer is formed when the material melts under the instantaneous high temperature of discharge, remains on the surface, and then solidifies due to rapid cooling by the working fluid. Its thickness increases with higher pulse energy.In the multi-pass cutting process of medium-speed WEDM, both current and voltage are progressively reduced, leading to lower single-pulse discharge energy and reduced discharge explosion force. As a result, the micro-pits caused by electric erosion on the machined surface become smaller, thereby reducing the surface roughness value.
Wire EDM overcomes the shortcomings inherent in traditional machining methods.
With the advancement of industrial refinement, traditional machining methods have become insufficient to meet the demands of high-precision and high-complexity part manufacturing. Against this backdrop, wire EDM technology has rapidly developed and found widespread application. This raises the question: which critical challenges in conventional machining does wire EDM actually address?
Machining of High-Hardness, Low-Toughness Materials:
Cemented carbide is characterized by high hardness and poor toughness, and it is typically machined by grinding. However, for small-sized or complex-shaped workpieces where grinding wheels cannot be applied, wire EDM is often used. For hard-to-machine, high-hardness materials that easily cause tool breakage and make conventional machining impossible, wire EDM, through discharge machining, enables effective processing.
Machining of Micro-Precision Components:
With the rapid development of advanced manufacturing, micro-precision components are playing an increasingly critical role across many industries. These components are characterized by small size, high accuracy, and complex geometries, which place extremely stringent demands on machining processes. Traditional methods such as cutting and milling often fail to meet the requirements for producing fine structures. Wire EDM, however, enables precise machining of difficult-to-process materials, including micro-holes, double internal tapers, and other complex inner-hole geometries.
Machining of Thin-Walled, Deformation-Prone Parts:
Thin-walled microstructures, known for their light weight, compact design, and good toughness, are increasingly applied in aerospace, precision instruments, automotive manufacturing, and the semiconductor industry. However, The fabrication of thin-walled microstructured components is a highly challenging task. In conventional machining, cutting forces and clamping forces generate residual stresses within the material, leading to dimensional changes that make it difficult to meet high-precision requirements. Non-contact wire EDM effectively avoids dimensional errors caused by residual stress during machining and elastic deformation during clamping. It is particularly suitable for cutting tough yet brittle thin-walled materials, reducing crack extend within the workpiece, and is considered an ideal process for manufacturing thin-walled microstructures.
Machining of Ultra-High-Thickness Workpieces:
With the rapid development of manufacturing, the demand for ultra-thick components has been increasing, particularly in the aerospace sector. Traditional machining methods struggle to process such workpieces. When using conventional machine tools, machining ultra-thick parts often requires customized tooling and involves multiple complex procedures, making the process neither economical nor practical. In contrast, high-speed reciprocating wire EDM introduces the working medium into the kerf via the electrode wire, which makes it highly suitable for cutting ultra-thick workpieces.
Machining of Complex-Shaped Parts:
In traditional machining, producing complex shapes, narrow slots, or sharp corners on molds is often difficult because the cutting tool may be unable to access or process such features. Specifically, when machining sharp corners, the tool’s radius limits make it impossible to achieve a true sharp edge. For small-radius corners, extremely small-diameter tools are required, which are prone to breakage, inefficient, and costly. When machining complex workpieces with varying radii or tapers, multiple setups, frequent tool changes, and complicated programming are often necessary, leading to long production cycles. Moreover, during cutting, milling or turning tools continuously wear out, and variations in cutting forces cause dimensional fluctuations, reducing consistency in mass production. Wire EDM, by contrast, offers significant advantages in machining products with sharp corners, small radii, and taper features.
Complex and High-Difficulty Part Machining? Leave It to Medium-Speed Wire EDM
Our company is equipped with two Baqi medium-speed wire EDM machines. Baqi medium-speed wire EDM is a hybrid wire-cutting system in which the term “medium-speed” does not simply refer to a speed level between fast and slow, but rather emphasizes a cutting process centered on multiple reciprocating passes. This approach reduces material deformation and molybdenum wire loss during cutting, thereby enhancing machining accuracy. By flexibly adjusting the wire feed speed, the equipment enables precise control over workpiece quality.
We are capable of machining high-hardness parts, complex precision structures, and thin-walled, deformation-prone components. We ensure extremely high fitting accuracy, superior surface quality, and consistent mass production. In addition, we help customers save on costly material expenses, streamline production processes, and ultimately reduce overall costs while shortening product development cycles.
At present, by leveraging advanced medium-speed wire EDM technology, we are able to machine a wide range of parts, including various stamping dies, micro-shaped holes, narrow slots, and complex workpieces, as well as templates and forming tools, metallurgical dies, cavity dies, drawing dies, and forming dies. We are also highly skilled in machining hard materials, cutting thin plates, and manufacturing both internal and external gears. In particular, we hold significant advantages in handling multi-variety, small-batch, and single-piece production.