About the technical status of fast-moving wire, middle-moving wire and slow-moving wire

With the development of science and technology, machinery manufacturing technology has undergone profound changes. As the society’s demand for product diversification is stronger, the proportion of multi-variety, medium and small batch production has increased significantly. The use of traditional ordinary processing equipment for medium-wire wire cutting machine tools has been difficult to meet the high-efficiency, high-quality, and diversified processing requirements. The application of technology greatly shortens the preparatory time of mechanical processing, and continuously improves the automation level of the whole process of mechanical processing. At the same time, it also enhances the ability of the manufacturing system to adapt to changes in various production conditions.

Wire cutting machine tools are divided into: medium wire, slow wire, and fast wire all refer to EDM wire cutting machine tools. Wire cut Electrical Discharge Machining (WEDM).

1. What is medium-speed Wire cut Electrical Discharge Machining? Medium-speed Wire cut Electrical Discharge Machining (Medium-speed Wire cut Electrical Discharge Machining abbreviated as MS-WEDM) belongs to the category of reciprocating high-speed wire-moving EDM wire cutting machines. The multi-cutting function is realized on the wire electric discharge machine, which is commonly called "medium wire wire cutting". The middle wire technology pointed out here that the so-called “medium wire” does not mean that the wire speed is between high and low speed, but a compound wire cutting machine tool, that is, the principle of wire feeding is to use high speed (8-12m) during rough machining. /s) Wire feeding, low speed (1-3m/s) wire feeding is used during finishing, so that the work is relatively stable, the jitter is small, and the error caused by material deformation and molybdenum wire loss is reduced through multiple cuts, so that the processing quality is also improved. Relatively improved, the processing quality 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, the middle wire technology has concluded 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 surface quality requirements of the machined surface. In fact, the finishing process is a kind of electric spark grinding. The wire-moving method can adopt the low-speed wire-moving speed-limiting feed just like the second cutting. During the processing of the middle wire technology, it is necessary to pay attention to the deformation treatment for multiple cuts, because when the workpiece is cut on-line, with the effect of the original internal stress and the processing thermal stress generated by the spark discharge, it will produce non-directional, Irregular deformation will cause uneven thickness in the subsequent cutting, which affects the processing quality and 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 completely 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.

2. Fast wire is a kind of wire EDM, also called high-speed wire EDM (WEDM-HS). The electrode wire (usually molybdenum wire) is used for high-speed reciprocating motion, and the wire speed is 8-10m. /s, the electrode wire can be used repeatedly, the processing speed is high, and the wire is easy to cause the electrode wire to jitter and stop when reverse, which reduces the processing quality. It is the main type of production and use in my country, and it is the original wire EDM in my country. Processing mode. In 1960, the Soviet Union first developed the profiling wire cutting machine tool. China also developed a similar machine tool in 1961. Early wire cutting machine tools used electric profiling to control the cutting trajectory. At that time, due to the low cutting speed, it was difficult to manufacture the master model, and it was only used for processing narrow slits that were difficult to solve by other processing methods in the electronics industry. In 1966, China successfully developed a high-speed wire cutting machine tool using emulsion and a fast wire mechanism, and successively adopted digital control and photoelectric tracking control technology. Since then, with the continuous development of pulse power supply and digital control technology and the application of multiple cutting processes, the cutting speed and processing accuracy have been greatly improved.

3. What is a slow-moving wire cutting machine tool? The electrode wire of the low-speed wire cutting machine uses copper wire as the tool electrode. Generally, it moves in one direction at a speed of less than 0.2m/s, and applies 60~ between the copper wire and the workpiece material such as copper, steel or super-hard alloy. A pulse voltage of 300V and a gap of 5-50um should be maintained. The gap is filled with insulating media such as deionized water (close to distilled water), so that spark discharge occurs between the electrode and the workpiece, which are consumed and corroded by each other, and electricity is applied to the surface of the workpiece. Numerous small pits are eroded. Through the monitoring and control of NC control and the execution of servo mechanism, this discharge phenomenon is uniform and consistent, so that the processed object can be processed, making it a product that meets the required size and shape accuracy. At present, the accuracy can reach 0.001mm, and the surface quality is close to the grinding level. The electrode wire is no longer used after discharge, and uses a non-resistance anti-electrolysis power supply, generally with automatic wire threading and constant tension devices. The work is stable, uniform, small jitter, high processing accuracy, and good surface quality, but it is not suitable for processing large thickness workpieces. Due to the precise structure of the machine tool, the high technical content and the high price of the machine tool, the use cost is also high. In the early days, one-way wire EDM wire-cutting machine tools were unique to foreign companies. Although Taiwan's low-speed wire EDM wire-cutting machine started relatively late, it has developed rapidly in recent years. One of its key measures is to jointly fund the development of key technologies by a number of home appliance processing machine tool manufacturers, and with limited support from relevant departments, the Taiwan Institute of Industrial Technology has invested a large amount of manpower and material resources in the development of key technologies. After more than 10 years of research, breakthroughs have been made in key technologies such as control systems and power supplies. The low-speed wire-moving wire EDM manufactured by various Taiwanese companies should currently be in the range of mid-range machines. In the past 3 years, it will reach an annual growth rate of 20% to 30%. It is estimated that in the next 5 years, Taiwan’s low-speed wire-moving wire EDM will be The annual output can reach 2,000 units, which can account for more than 25% of the world market. The low-speed wire EDM wire cutting machine has high technical content, good market prospects, and high returns. It is the "place of competition" and "strategic high ground" for all manufacturers in the electrical machining industry. It can also be said that whoever has mastered the technology of low-speed wire-moving wire EDM will have the opportunity for the next step of enterprise development and growth. In order to seize the Chinese market, electrical machining machine tool manufacturers in Japan, Switzerland, and Taiwan set up factories in mainland China to produce such machine tools. With the support of the special fund of the Ministry of Science and Technology, our country’s scientific and technological workers have invested a large amount of research and development strength, and have completed the research and development of a new generation of low-speed wire EDM wire cutting machines, and have made major breakthroughs. Now they have independent intellectual property rights. The product has occupied a certain market share, and its performance indicators can reach the level of mid-range machines. At present, some domestic companies hope to develop low-speed wire EDM wire cutting technology through cooperation with related Taiwanese companies.

　Compared with the one-way low-speed wire EDM wire-cutting machine tool, the reciprocating high-speed wire EDM wire-cutting machine still has a big gap in the average productivity, cutting accuracy and surface roughness and other key technical indicators. In response to these gaps, at the beginning of this century, several domestic manufacturers of high-speed reciprocating wire EDM wire cutting machines realized multiple cutting processes on high-speed wire machines (this type of machine tool is commonly known as "Medium Speed Wire cut" Electrical Discharge Machining). The so-called "middle wire" does not mean that the wire speed is between high and low speed, but a composite wire cutting machine. The wire principle is to use 8-12m/s high-speed wire during rough machining and use in fine machining. 1-3m/s low-speed wire walking, so that the work is relatively stable, with little jitter, and the error caused by material deformation and molybdenum wire loss is reduced through multiple cuttings, so that the processing quality is relatively improved, and the processing quality can be in the high-speed wire machine. Between and 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. After several years of development, almost all domestic manufacturers of high-speed wire EDM wire-cutting machine tools are wire-cutting in production and sales, but it turns out that not all reciprocating wire EDM wire-cutting machines can perform multiple cuts. In other words, not all reciprocating wire EDM wire cutting machines can achieve good process results after using multiple cutting techniques. Multi-cutting is a comprehensive technology. It involves the CNC precision of the machine tool, pulse power supply, process database, wire feeding system, working fluid, and a large number of process problems. It is not simply adding a set to the high-speed wire feeding machine. It can be realized by the wire transport frequency conversion speed control system. Only those reciprocating wire EDM wire cutting machines with high manufacturing precision and creating multiple cutting conditions in various aspects can perform multiple cutting and non-stripe cutting, and obtain remarkable results. Process effect. Therefore, our production enterprises must pay full attention to this problem, and must do it according to system engineering, really make good use of this technology, and make this product do a good job. For example, in order to further improve the accuracy of the machine tool itself, some companies have adopted DC or AC servo motors as the drive unit to directly drive the ball screw. At the same time, it has adopted a full closed loop control with pitch compensation function, which can be controlled by numerical control. The system compensates and corrects the positioning accuracy error of the machine tool. On the premise of ensuring accuracy, reduce the decrease in machining accuracy caused by long-term use and extend the service life of the machine tool. The wire transport system uses a special (mostly diamond) electrode wire holder to keep the electrode wire relatively stable and reduce the tension change of the electrode wire during processing. The cooling system changes the commonly used extensive cooling method, adopts multi-stage filtration and controls key parameters such as dielectric constant to ensure the smooth progress of finishing. The control software provides an open processing parameter database, and the corresponding processing parameters can be selected according to the material texture, thickness, roughness and other conditions. I believe that through our efforts, the multiple cutting technology will be more perfect, and the reciprocating wire EDM wire cutting technology will also be better applied and developed.

After the reciprocating wire EDM machine adopts multiple cutting technology, although the processing quality has been significantly improved, it still belongs to the category of high-speed wire EDM, and the cutting accuracy and smoothness are still greater than that of low-speed wire machines. The gap, and the retention of precision and finish needs to be further improved. "Medium wire machine" has the characteristics of simple structure, low cost and low consumption, so it also has room for survival. The current standard is still the relevant standard of high-speed wire machine. Therefore, the manufacturer must publicize the user Attention, we must seek truth from facts.