Nano-precision Wire EDM
In component manufacturing workshops, wire EDM is an essential part of mechanical parts production. Among these, slow-speed wire EDM is one of the most precise wire-cutting techniques available. Wire EDM, abbreviated as WEDM, stands for Wire Electrical Discharge Machining. Its working principle involves using a continuously moving thin metal wire (called the electrode wire) as an electrode to generate pulsed electrical discharges on the workpiece, vaporizing tiny amounts of metal locally and cutting it into the desired shape.
Advantages of Wire EDM Machining Technology
Wire EDM is primarily used for machining workpieces with complex shapes and fine precision, such as forming tools, templates, metal electrodes for EDM, various micro-holes and slots, narrow gaps, and arbitrary curves. During the machining process, the initial cutting and shaping generally use higher current, while subsequent passes use lower current. It is also possible to control the minimum pulse width. EDM machines can be classified by wire speed into high-speed reciprocating wire EDM machines (commonly known as fast wire EDM), low-speed unidirectional wire EDM machines (commonly known as slow wire EDM), and vertical self-rotating wire EDM machines.
Different Grades of Slow-Speed Wire EDM Machining Technology
(1) Top-tier Slow-Speed Wire EDM Machines
Top-tier slow-speed wire EDM machines represent the highest level of slow wire EDM technology. This machining method uses a continuously moving electrode wire to generate pulsed electrical discharges on the workpiece, eroding metal and cutting it into shape. These high-precision EDM machines support the production of precision components and mold machining for industries such as medical and aerospace.Such machines can achieve machining accuracy within 0.002 mm, with maximum cutting efficiency of 400–500 mm²/min and surface roughness down to Ra 0.05 µm, delivering near-perfect surface quality with minimal recast layer. They are capable of micro-machining using electrode wires as small as φ0.02 mm. Most machines are equipped with thermal balance systems, and some perform cutting and machining in oil.These machines feature a high degree of automation and CNC programmability, enabling direct precision mold manufacturing, with mold lifespans comparable to those achieved through mechanical grinding. Top-tier slow-speed wire EDM machines are typically manufactured in Europe, the United States, and Switzerland.
(2) High-end Slow-Speed Wire EDM Machines
These machines feature automatic wire threading, resistance-free anti-electrolysis power supplies, and comprehensive thermal stability systems. They can cut with electrode wires as small as φ0.07 mm, achieving accuracy of approximately ±0.003 mm, with maximum machining efficiency exceeding 300 mm²/min and surface roughness reaching Ra < 0.2 µm. They are equipped with real-time workpiece cross-section monitoring and discharge power optimization. These machines are also widely used for precision stamping die machining. High-end slow-speed wire EDM machines are predominantly manufactured in Japan and Switzerland.
(3) Mid-range Slow-Speed Wire EDM Machines
Their configuration and performance meet the requirements of most precision wire EDM applications in China. These machines typically use resistance-free anti-electrolysis power supplies and feature submerged machining and taper cutting capabilities. Practical maximum machining efficiency ranges from 150 to 200 mm²/min, with optimal surface roughness reaching Ra < 0.4 µm and cutting accuracy up to ±0.005 mm. They generally use electrode wires of φ0.1 mm or larger and are equipped with collision protection systems to prevent damage from programming errors or operator mistakes, with automatic wire threading available or optional.
These mid-range slow-speed wire EDM machines are usually manufactured in Chinese factories by Swiss and Japanese companies, and some Taiwanese machines also reach comparable technical levels.
(4) Entry-level Slow-Speed Wire EDM Machines
Their configuration and performance meet the requirements of standard mold and component machining in China. They generally use single- or double-pass cutting processes and can reliably achieve surface finishes of Ra 0.8 µm and machining accuracy of ±0.008 mm. Most can only use electrode wires of φ0.15 mm or larger. The microstructure and corner quality of machined surfaces are somewhat inferior compared to advanced machines. These entry-level machines are typically domestically developed in China or manufactured by Taiwanese companies.
Our company is equipped with West Japanese slow-speed wire EDM machines.
TheSeibu M50B is a slow-speed wire EDM model currently used in our company, offering significant advantages over standard models:
Tilt/Angled Cutting Support:
Some machines only support very small U/V tilt angles or have limited angled cutting capabilities. The West Japanese M50B provides ±60 mm U/V travel and ±10° angled cutting, allowing tilt cuts even in relatively thick workpieces. For parts requiring beveled edges, inclined walls, or angled/tilted surfaces in complex cavities, this feature reduces machining difficulty and the number of required operations.
Wire Threading / Automation Setup Time:
Standard machines often require manual wire threading after each segment or lengthy preparation for multiple operations, resulting in high labor involvement. The M50B comes standard with automatic wire threading and wire feed systems, improving production rhythm and efficiency. It features an auto wire threader (AWT) and an automatic wire feed (AWF) system. The standard accessories also include well-integrated hydraulic, tank, cooling, and filtration systems.
Stability of Accuracy Over Time, Temperature, and Machine Wear:
Machines with ball screws or non-scraped beds tend to develop backlash and thermal deformation over prolonged use, reducing accuracy. Seibu uses hand-scraped cast beds, a stable structural design, and effective thermal management to maintain precision. The nominal accuracy is approximately ±3 µm (pitch accuracy). This stability is crucial for applications requiring precision cutting and minimal cumulative error over multiple passes, such as mold cavities and medical device components.
Surface Finish and Post-Cutting Touch-Up Requirements:
Some machines produce rough cut surfaces that require subsequent polishing or compensation. The M50B, with features such as the Super Fine Finish circuit, can directly achieve high-quality surface finishes, reducing the need for post-processing. Its work envelope is approximately X×Y×Z = 500×350×310 mm (about 19.7×13.8×12.2 in). For molds or parts requiring superior surface quality without extensive post-processing or polishing, this feature can save significant labor and time.
Workpiece Size and Thickness Limitations:
Some machines are suitable only for small to medium-sized workpieces, with limited capability for thick or large parts. The M50B’s work travel, table load capacity, and dimensions allow machining of larger and thicker workpieces. It supports a maximum workpiece weight of approximately 800 kg, with a flexible table size and fixture usage. For heavy workpieces, thick cavities, large castings, or metal blocks, such load capacity and table stability are essential.
Machine Structure and Build Quality:
Manufactured in Japan, the machine’s base material (castings) is hand-scraped to minimize deformation. It offers high rigidity and strong overall structural stability. This ensures better accuracy retention during long-term operation and under significant temperature fluctuations. Such qualities are particularly valuable for mold shops or companies with high precision requirements for fixtures.
Points to Note:
In certain situations, the M50B may not be the optimal choice:
While its accuracy of approximately ±3 µm is excellent, some ultra-high-end machines (such as Seibu’s MM series or specialized ultra-precision wire EDM machines) can achieve ±1 µm, which may be better suited for extremely fine or high-precision applications.
Cutting thickness and angled cuts may be limited at very high inclinations or with very thick workpieces. Even with ±10° angled cutting capability, the effect and surface quality on thicker workpieces may be slightly affected.
Higher cost: Machines with high precision, automation, and superior structural design have higher purchase prices, maintenance costs, and operational requirements compared to basic wire EDM machines.