The development and advantages of wire-cutting machine tools

1. Basic theory

Experts pointed out that the so-called "emedium wir" does not mean that the wire speed is between high and low speed, but a composite wire cutting machine, that is, the principle of wire feeding is to use high-speed (8-12m/s) wire feeding during rough machining. , Use low-speed (1-3m/s) wire feeding during finishing, so that the work is relatively stable, the jitter is small, and the error caused by material deformation and molybdenum wire loss through multiple cuttings is reduced, so that the processing quality is relatively improved. It can be between the high-speed wire machine and the low-speed wire machine. Therefore, it can be said that what users call "medium wire feed" is actually the reciprocating wire EDM wire cutting machine borrows some processing technology of low speed wire machine, and realizes streak-free cutting and multiple cutting.

In practice, it is found that the first cutting task in multiple cuttings is mainly high-speed and stable cutting. High-peak current and longer pulse width can be used for high-current cutting to obtain higher cutting speed. The task of the second cutting is to fine-tune to ensure the machining dimensional accuracy. A medium standard can be used to make the roughness Ra after the second cut between 1.4 and 1.7 μm. In order to achieve the purpose of finishing, low-speed wire feeding is usually used, the wire feeding speed is 1～3m/s, and the tracking feed speed is limited to a certain range to eliminate the reciprocating cutting stripes and obtain the required machining dimensional accuracy. . The task of the third, fourth or more cuttings (currently the middle wire control software can achieve up to seven cuttings) is polishing and polishing. The minimum pulse width (currently the minimum frequency can be divided to 1μs) is used for polishing. However, the peak current varies with the quality of the processed surface. In fact, the finishing process is a kind of electric spark grinding, and the processing volume is very small, and the size of the workpiece will not change. The wire-moving method can adopt the low-speed wire-moving speed-limiting feed just like the second cutting. In the process of processing, multiple cuts also need to pay attention to the deformation treatment, because when the workpiece is cut online, with the effect of the original internal stress and the processing thermal stress generated by the spark discharge, it will produce non-directional and irregular deformation , So that the thickness of the subsequent cutting knife is uneven, which affects the processing quality and processing accuracy. Therefore, it is necessary to reserve different machining allowances according to different materials, so that the workpiece can fully release the internal stress and complete torsion deformation, and there can be enough margin for finishing cutting in the subsequent multiple cuttings, so that the final size of the workpiece can be guaranteed.

Second, the origin of domestic wire cutting machine tools


Wire-cutting machine tools originated in the early 1970s. Before the implementation of the market economy, the development of wire-cutting machine tools was relatively slow, mainly because China's electronics industry was relatively backward at that time, and the production plants of wire-cutting machine tools were all state-owned enterprises.

Although the technical ability is strong, but due to the disconnect from the market and the constraints of the planned economy, the WEDM machine tool produced not only has a high failure rate, but also has limited performance (only cutting 50mm thick, with an efficiency of 30mm²/min), but in any case This kind of wire-cutting machine tool is a kind of machine tool unique to China. Although it has lower accuracy compared with foreign wire-cutting machine tools, its manufacturing and use costs have absolute advantages. It is very suitable for those developing countries. It is precisely because of this potential market demand.

After the implementation of the market economy in China, many wire-cut machine tool manufacturers have emerged across the country. As a result, disordered competition has appeared in the wire-cutting market. Disordered competition has evolved into price competition. In order to reduce costs, some companies with poor technical strength have reduced production. Standards, coupled with the ineffective management of relevant national technical supervision agencies, have caused huge differences in the quality of wire-cutting machine tools from different manufacturers on the market. Some wire-cutting machine tools can be used for 10 years without loss of accuracy, and some can only be used for two years. The price of the WEDM of the same specification can vary by 100,000 RMB, which does cause great difficulties for users (especially foreign users). If they are not so good, they will be fooled. Then why these unqualified WEDMs can still be used? Appear on the market?

From the perspective of the social environment, China has not implemented a market economy for a long time, and some small wire-cut machine tool manufacturers are still in the stage of initial capital accumulation. These manufacturers often do not have the ability to manufacture the whole machine, and can only produce assembling. The whole process of quality control is not at all possible, and R&D and innovation are even more impossible. In addition, China’s current laws supporting the market economy are not yet mature, and local government protection is driven by interests, so these companies with no production capacity It will continue to survive. Judging from the current status quo, the country’s attitude towards this is naturally eliminated through market competition.

Third, the current status of the development of wire-cutting machine tools


Nowadays, the non-scientific name "middle wire" has become the code name for a class of high-end products in China's unique high-speed wire cutting machine. It is not only popular in the country but also gradually showing its foot in the international market. Many companies still believe in and are active. Committed to promoting the high-speed wire cutting machine to the world.

It is now recognized that multiple cutting can effectively improve the processing quality of high-speed wire EDM, but not all high-speed wire EDM can perform multiple cuts, or not all high-speed wire EDM The wire spark cutting machine can obtain good process results after using multiple cutting techniques. Only those high-speed wire cutting machines that have high manufacturing precision and created multiple cutting conditions in various aspects can perform multiple cutting and non-stripe cutting, and obtain significant process effects. After the high-speed wire cutting machine adopts multiple cutting technology, its processing quality is significantly improved, and it is close to the economical low-speed wire cutting machine, and the price and consumption of this machine tool are far lower than the low-speed wire electric discharge wire Cutting machine.

"At present, the technical strength of domestic enterprises is uneven, and the capital strength is also different. To bring out a new spring of high-speed wire cutting machines, first of all, we must pay attention to technological innovation. Only technology is sustainable. The basis and guarantee of development; thirdly, it is possible to adopt the way of enterprise alliances, led by stronger companies, and to unite or cooperate with related enterprises, to achieve resource sharing by maximizing strengths and avoiding weaknesses; thirdly, benign competition, rational competition, and avoid simplifying products. Prevent technological degradation. Now, our technical efforts have resulted in the popularity of the “middle silk”. This is a road worth continuing to explore. It is unique to China (except for mainland China, no country or region produces this type of machine tool). The high-speed wire EDM (WEDM-HS) of the manufacturer) has developed rapidly since it was successfully developed in the late 1960s due to its simple structure, low cost, good process effect, and low consumption during use. , Has become an indispensable process equipment in the manufacturing industry.

Yu Zhongqiang, Vice President of Sales of Sanqi Middle Wire, believes that the current domestic middle wire technology has been further improved, and it is close to slow wire in terms of accuracy, smoothness, and speed. It can replace part or even half of slow wire processing. Some companies have achieved complete Closed loop, basically meeting the needs of medium-sized mold factories.

4. Conclusion and outlook

The middle wire machine tool is a unique electrical processing machine tool in my country, which has a wide range of applications in the field of mold manufacturing and parts processing, and occupies a considerable weight in the middle and low-end markets. At present, how to develop the middle wire machine tool is a topic of great concern to the electrical machining industry. We must absorb the successful experience of foreign countries, maximize the strengths and avoid weaknesses, directly apply the latest achievements of today's computer technology, develop a powerful PC-based CNC system as soon as possible, and lay a good foundation for the development of medium-threaded machine tools from the hardware; at the same time pay attention to artificial intelligence technology. In combination with high-speed wire cutting machine, computer software technology is used to improve the performance of the machine tool. In addition, strengthen the research of the machine tool body and carry out the application of multiple cutting technology, so that the overall processing level of the machine tool has been greatly improved, and the competitiveness of the high-speed wire cutting machine in the market is continuously enhanced. While using new technology and new technology, we must also pay attention to the in-depth and detailed basic theoretical and experimental research on the law of wire EDM, which is also a very important link.