Development History of WEDM
In the 1960s, China introduced its first slow-speed wire-electrode discharge machining (WEDM) machine. This early technology used a thin brass wire to cut embossing modules on steel workpieces immersed in kerosene. However, the process was extremely slow, achieving only a few square millimeters per minute. Despite its limitations, this marked the beginning of WEDM in China. By the early 1970s, Zhang Weiliang developed a high-speed wire-cutting system using a reciprocating infinite loop wire. Although still based on die-cutting methods, this innovation increased processing efficiency to about 10 mm²/min. Under the guidance of Shanghai’s Science and Technology Supervisor, Fudan University designed a numerical control system using discrete components, leading to the creation of the “fast-cut wire†or “Fudan-type†machine. Later, to meet the needs of plastic mold manufacturing, the team independently developed a taper device and introduced single-board computer control, eventually evolving into modern microcomputer CNC systems. Meanwhile, Western manufacturers also advanced their slow-speed WEDM machines from die-cutting to numerical control, known as “slow wire cutting.†These machines also supported taper cutting and were controlled via computer systems. In the public perception, fast-cut wire EDM is often seen as a low-end machine with an accuracy of 0.01–0.03 mm and poor surface finish, characterized by black-and-white streaks. In contrast, imported slow-wire machines can achieve surface roughness as low as 0.2 μm through multiple cuts. To bridge this gap, the so-called “medium wire†method emerged, where closed-loop control improved precision and reduced surface roughness after multiple cuts. However, due to the two-step reciprocating motion, some residual errors remained.Summary Analysis of Wire-Feeding Methods
Through analysis of various WEDM machines globally, the mechanical structures can be categorized into four types: 1) Disposable one-way wire, 2) Infinite reciprocating cycle wire, 3) Rotating infinite reciprocating cycle wire, and 4) One-way infinite loop wire. (1) The disposable one-way wire, commonly known as "slow wire cutting," is primarily used in foreign WEDM machines. It offers high positioning accuracy and stable surface quality due to constant tension and precise control. However, it suffers from low cutting speed, poor cooling, and limited thickness capability, making it less efficient for large parts. (2) The infinite reciprocating cycle wire is a Chinese invention. Developed by Zhang Weiliang, this method uses guide wheels and allows for high-speed cutting. While it enables cutting thick materials up to 1 meter, it has issues like unstable wire tension, surface streaks, and lower time utilization due to the need for commutation. (3) The rotating infinite reciprocating cycle wire, invented by Dr. Yang Xinsheng, aimed to combine the benefits of both high speed and precision. Though promising, it faced challenges such as limited regional support and funding, preventing widespread adoption. (4) The one-way infinite loop wire represents the future of high-end WEDM in China. It combines the advantages of both slow and fast wire methods while eliminating their drawbacks. It allows for continuous, high-efficiency cutting without the need for commutation, offering adjustable speeds, stable tension, and excellent surface finish.Innovative Concept of One-Way Infinite Loop Wire
The one-way infinite loop wire-cutting method is a groundbreaking invention. It features two key technical aspects: first, the ability to connect the ends of the wire seamlessly; second, the design of a flexible storage tube that allows the wire to move continuously without reversing. To connect the wire, advanced techniques such as laser or electron beam welding are used, creating a smooth joint. Alternatively, special end shapes and controlled melting can also achieve consistent wire diameter. Both methods require precise mechanisms, which have been patented. The flexible storage tube is another crucial component. Unlike traditional rigid cylinders, it allows the wire to move smoothly from one end to the other, enabling a true one-way infinite loop. This design eliminates the need for reciprocation, improving efficiency, surface quality, and precision. The advantages of the one-way infinite loop wire include higher time utilization, smoother surface finish, better positioning accuracy, and more stable discharge conditions. For example, compared to middle-wire machines, the surface irregularities can be reduced from 0.02 mm to nearly zero. Additionally, it can achieve high-precision cuts in one or two passes, matching the performance of imported slow-wire machines. This innovation marks a significant step forward for Chinese WEDM technology, bringing it closer to global standards in high-end precision machining.Electric mosquito swatter is a kind of small household appliance products, mainly used to kill mosquitoes, flies, moths and other insects. It through the electronic high voltage technology, the use of 1850V high voltage to effectively destroy these pests, has the advantages of practical, convenient, no chemical pollution, safety and health, so it is widely welcomed, become the summer best-selling small household appliances products. The electric mosquito bat is usually composed of three layers of metal mesh, the outer metal mesh and the middle layer are not directly connected, and maintain a certain distance. When the switch is pressed, the direct current in the battery passes through the oscillation circuit and the boost circuit, eventually reaching a high voltage above 2000 volts. This design allows the mosquito to be waved through the electrostatic field and electrical grid discharge to destroy the insect, without causing harm to the human body.
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