CNC wire-cut EDM includes rapid wire processing and wire processing, which are widely used in the mold manufacturing industry. What are the current developments in the processing efficiency, cutting accuracy, and surface quality of these two technologies? Development status of fast wire processing technology As the name implies, fast wire processing is named after the high speed wire movement of the electrode wire during the cutting process. Fast wire processing machine is China's original electric processing machine. After decades of continuous improvement and development, it has become an important processing method in the manufacturing industry. It can meet the requirements of middle and low-grade mold processing and other complex parts manufacturing, and occupies a considerable weight in middle and low-end markets. The biggest advantage of fast wire processing machines is that they have a good performance-to-price ratio. Because of its practicality and economy, it has a larger market in China. The traditional fast wire processing adopts a one-time cutting process, the processing efficiency is about 40 mm2/min, the surface roughness is about Ra 3.0 μm, the surface has a distinct line pattern, and the processing accuracy is about 0.02 mm. In order to improve the processing quality, the wire cutting machine tool manufacturers refer to multiple cutting processes and improved the relevant parts of the machine tool. The so-called “take-wire machine tool†has emerged. The numerical control precision, pulse power supply, wire drawing system, and process database of the machine tool have been greatly improved. Improve the processing accuracy and improve the surface quality. At present, the technical specifications of the middle wire processing machine: the efficiency of one cutting is 180mm2/min, the surface roughness after multiple cutting is Ra≤1.0μm, the average efficiency at this time is 50mm2/min, the surface gloss is processed No significant cutting stripes, processing accuracy 0.01mm, electrode wire loss ≤ 0. 01 mm / 200,000 mm2. These performance indicators seem to have been relatively good, but it should be noted that access to these indicators need to ensure that all aspects, once there is an access, such as the concentration of the working fluid, the loss of the electrode wire changes, it will affect the stability of the processing quality. The typical manufacturers of wire-drawing machine tools in production include Suzhou Sanguang, Suzhou Hanchi, Shanghai Special, Beijing Ande, Suzhou Baoma, Suzhou Spark, and Shanghai Mass. The status of development of slow wire processing technology The manufacturing precision and surface quality requirements of precision, complex, and long-life stamping dies have been continuously improved. The rapid traverse processing technology can no longer meet the requirements for the manufacture of precision dies. This status quo has promoted the rapid development of the traversing wire processing technology, and its various process indicators. It has reached a fairly high level and is an irreplaceable alternative to other processing technologies. 1. Development status of the slow wire processing technology (1) Improved machining accuracy Multiple cutting technology is the fundamental means to improve the precision and surface quality of the slow walking wire. Generally, it is formed by one cut and the secondary cutting improves the precision, and the cutting more than three times improves the surface quality. Due to the lag of the electrode wire when cutting corners, the corners may collapse. In order to improve the corner cutting accuracy, more dynamic corner processing strategies have been adopted. Such as: automatically change the processing speed, automatically adjust the water pressure, control the processing energy. The advanced high-precision finishing circuit used in the advanced wire moving machine is an effective technique to improve the straightness of the machined workpiece. The accuracy of thick processing is significantly improved; for small round, narrow, narrow and fine parts For micro-finishing, the top CNC low-speed wire EDM machine can use 0.02-0.03 mm wire to cut. In order to ensure high-precision machining, the machine's mechanical accuracy, pulse power supply accuracy, and servo control accuracy (including control of the mechanical movement, pulse parameters, wire drawing system, and working fluid system) have reached a very high level. The use of water temperature cooling device makes the internal temperature of the machine tool the same as the water temperature, which reduces the thermal deformation of the machine tool. The closed-loop digital cross (or straight) flow servo control system ensures excellent dynamic performance and high positioning accuracy. The machining accuracy can be controlled at several micrometers. Within, precision positioning can achieve 0.1μm equivalent control; use immersion processing, reduce the thermal deformation of the workpiece; servo motor, closed loop wire tension control; using voltage modulation knife power to achieve high precision tooling, tooling accuracy up to 0.002 mm , does not damage the workpiece, whether wet or dry. (2) Perfect surface quality The advanced low-speed wire processing machine uses a non-electrolytic pulse power source with an average voltage of zero, and the destruction of the electrolysis has been minimized. In addition, due to the improvement of the pulse power supply, high peaks and narrow pulse widths (microseconds) are commonly used. Most of the material is thrown out of the gas phase, which takes away a lot of heat, and the surface temperature of the workpiece does not go up. The phenomenon of cracking is large. Reduced; not only high processing efficiency, but also greatly improve the surface quality. The use of an electroless power source for wire-cut electrical discharge machining allows surface destructive layers to be controlled below 2 μm. The wear resistance of the cutting edge of the hard alloy die is no different from that of the grinding. It is even better than the mechanical grinding process. More and more parts are processed by "cutting and grinding". (3) Improvement of processing efficiency Due to the development of nanosecond pulse current source technology and detection, control, and anti-jamming technology, the processing efficiency of the slow-wire processing machine is also increasing, and the highest processing efficiency of the current advanced wire processing machine is up to 500mm. 2/min. The processing efficiency of large-thickness workpieces is of practical significance. For example, when cutting 300 mm thick workpieces, the machining efficiency can reach 170 mm2/min. For the processing of workpieces with varying thickness, the thickness of the workpieces is automatically detected, and the processing parameters are automatically adjusted to prevent broken filaments and achieve the highest processing efficiency in this state. In addition, the advanced automatic threading machine introduces the automatic threading technology, automatic threading time <15 s to improve the efficiency of the processing operation; introduced dual wire automatic exchange technology, can use 0.20 ~ 0.02 mm wire electrode automatically double Wire switching processing. The first cutting is performed with coarse wire, the general wire diameter is 0.25 mm, to improve the processing efficiency, and can be cut without core; then the filament is used for trimming, generally 0.10 mm filaments are used to cut small round corners, and Improve the accuracy, the overall savings of 30% to 50% of the cutting time. (4) Development of Automation, Intelligence, and Informatization During the processing, in order to reduce human intervention and ensure that the desired process indicators are achieved, the automation, intelligence, and informationization of the slow wire processing have achieved corresponding development. The full process expert system of the slow-wire processing machine gives complete sets of parameters according to the processing requirements. Including not only common electrode wire number and corresponding workpiece materials, but also processing parameters such as PCD, PCBN and other special materials, depending on whether the upper and lower nozzles are in contact with the workpiece, how much the distance is, whether it is refined in the cutting wind, or open surface fine The optimization, precision, surface roughness, and efficiency of a preferred machining strategy to generate the respective criteria; the discharge expert system deals with the random factors in the cutting, cutting in, cutting out, section change, center cutting, near edge cutting, large In the case of high-speed cross-section cutting, adaptive control strategies and automatic control functions are used in the machining process to achieve stable and efficient wire processing. The automatic holeless detection function is also practical. In the case of automatic skipping processing, if the pre-bored hole is forgotten or the hole position is offset, the machine tool will automatically move to the next pre-hole, which will prevent the machine from stopping during unmanned machining. When a short circuit occurs after threading, the position of the short circuit can be automatically searched to improve the reliability of continuous unattended operation. The CNC system of the machine tool is equipped with a standardized mechanical interface to form an intelligent manufacturing system. Through the robots of the 3R system or the EROWA system, the automatic exchange of workpieces (pallets) can be easily achieved, and expert systems and wire electrode automatic exchange technology can be used. Automatically complete all processing. 2. The technical level of various grades of wire walking machine tools The machine can be divided into top grade, high grade, mid-range, and entry grades. The typical manufacturers of the slow-threading machine tools include Swiss GF Machining Solutions (formerly Agie Charmilles), Japanese Makino, Japanese Mitsubishi, Japanese Sodick, Western Japan, and Japanese Franks. (1) Top-level wire walking machine This kind of wire walking machine represents the highest level currently, mainly made in Switzerland and Japan. The machining accuracy of this type of machine tool can be guaranteed within ±0.002 mm, the maximum processing efficiency can reach 400-500mm2/min, the surface roughness can reach Ra0.05μm, and the machined surface quality is perfect. The surface has almost no deteriorating layer. The Φ0.02 mm electrode wire is used for micro-finishing. Most of the machines have a thermal balance system. Some machine tools are used for cutting in oil. This kind of machine tool has complete functions and high degree of automation. It can directly complete the precision machining of the mold. The life of the processed mold has reached the level of mechanical grinding. (2) High-grade walking wire processing machine This type of machine tool is basically produced by Swiss and Japanese companies. It has automatic threading function, no resistance electrolysis power supply, integrated thermal constant system, can use Φ0.07 mm wire to cut, the accuracy is about ± 0.003 mm, the highest processing The efficiency can reach 300mm2/min or more, and the surface roughness can reach Ra<0.2μm. It can timely detect the change of workpiece cross-section and optimize the discharge power function in real time. Such machine tools are also widely used for precision stamping die machining. (3) Mid-range wire moving machine This machine is generally produced by Swiss and Japanese companies in China's manufacturing plant. The technical level of some Taiwanese machines can also reach this level. Its configuration and performance meet the requirements of most of the domestic precision wire cutting processing. Generally use non-resistance anti-electrolysis power supply, with immersion water processing, taper cutting function. The practical maximum processing efficiency is 150～200 mm2/min, the best surface roughness is Ra<0.4μm, the cutting accuracy is up to ±0.005mm, generally the electrode wire with Φ0.1mm and above is used for cutting, equipped with Collision protection system can avoid collision damage caused by programming errors or misoperation, equipped with or optional automatic threading mechanism. (4) Entry Level Walking Wire Machine Tool This type of machine tool is usually a Taiwanese machine tool or a domestically-developed machine tool. The configuration and performance of the machine tool meet the processing requirements of ordinary molds and parts in the country. Generally use one more one to repair one, cut one to repair the two processes, can be stable to achieve a surface finish of Ra0.8μm, processing accuracy of ± 0.008mm, most can only use the electrode wire of 0.15mm and above to cut, the surface of the processing of fine organization There is a certain gap between the corner and the advanced machine tools. In general, compared with the wire processing machine, the walking wire processing machine has obvious advantages in processing efficiency, precision, and surface quality. Although the price of the wire spinning machine is relatively expensive, it will be increasingly used in various processing fields with the rapid development of the manufacturing industry. Development status of fast wire processing technology As the name implies, fast wire processing is named after the high speed wire movement of the electrode wire during the cutting process. Fast wire processing machine is China's original electric processing machine. After decades of continuous improvement and development, it has become an important processing method in the manufacturing industry. It can meet the requirements of middle and low-grade mold processing and other complex parts manufacturing, and occupies a considerable weight in middle and low-end markets. The biggest advantage of fast wire processing machines is that they have a good performance-to-price ratio. Because of its practicality and economy, it has a larger market in China. The traditional fast wire processing adopts a one-time cutting process, the processing efficiency is about 40 mm2/min, the surface roughness is about Ra 3.0 μm, the surface has a distinct line pattern, and the processing accuracy is about 0.02 mm. In order to improve the processing quality, the wire cutting machine tool manufacturers refer to multiple cutting processes and improved the relevant parts of the machine tool. The so-called “take-wire machine tool†has emerged. The numerical control precision, pulse power supply, wire drawing system, and process database of the machine tool have been greatly improved. Improve the processing accuracy and improve the surface quality. At present, the technical specifications of the middle wire processing machine: the efficiency of one cutting is 180mm2/min, the surface roughness after multiple cutting is Ra≤1.0μm, the average efficiency at this time is 50mm2/min, the surface gloss is processed No significant cutting stripes, processing accuracy 0.01mm, electrode wire loss ≤ 0. 01 mm / 200,000 mm2. These performance indicators seem to have been relatively good, but it should be noted that access to these indicators need to ensure that all aspects, once there is an access, such as the concentration of the working fluid, the loss of the electrode wire changes, it will affect the stability of the processing quality. The status of development of slow wire processing technology The manufacturing precision and surface quality requirements of precision, complex, and long-life stamping dies have been continuously improved. The rapid traverse processing technology can no longer meet the requirements for the manufacture of precision dies. This status quo has promoted the rapid development of the traversing wire processing technology, and its various process indicators. It has reached a fairly high level and is an irreplaceable alternative to other processing technologies. 1. Development status of the slow wire processing technology (1) Improved machining accuracy Multiple cutting technology is the fundamental means to improve the precision and surface quality of the slow walking wire. Generally, it is formed by one cut and the secondary cutting improves the precision, and the cutting more than three times improves the surface quality. Due to the lag of the electrode wire when cutting corners, the corners may collapse. In order to improve the corner cutting accuracy, more dynamic corner processing strategies have been adopted. Such as: automatically change the processing speed, automatically adjust the water pressure, control the processing energy. The advanced high-precision finishing circuit used in the advanced wire moving machine is an effective technique to improve the straightness of the machined workpiece. The accuracy of thick processing is significantly improved; for small round, narrow, narrow and fine parts For micro-finishing, the top CNC low-speed wire EDM machine can use 0.02-0.03 mm wire to cut. In order to ensure high-precision machining, the machine's mechanical accuracy, pulse power accuracy, and servo control accuracy (including control of the mechanical movement, pulse parameters, wire drawing system, and working fluid system) have reached a very high level. The use of water temperature cooling device makes the internal temperature of the machine tool the same as the water temperature, which reduces the thermal deformation of the machine tool. The closed-loop digital cross (or straight) flow servo control system ensures excellent dynamic performance and high positioning accuracy. The machining accuracy can be controlled at several micrometers. Within, precision positioning can achieve 0.1μm equivalent control; use immersion processing, reduce the thermal deformation of the workpiece; servo motor, closed loop wire tension control; using voltage modulation knife power to achieve high precision tooling, tooling accuracy up to 0.002 mm , does not damage the workpiece, whether wet or dry. (2) Perfect surface quality The advanced low-speed wire processing machine uses an electrolysis-free pulse power source with an average voltage of zero, and the destruction of the electrolysis has been minimized. In addition, due to the improvement of the pulse power supply, high peaks and narrow pulse widths (microseconds) are commonly used. Most of the material is thrown out of the gas phase, which takes away a lot of heat, and the surface temperature of the workpiece does not go up. The phenomenon of cracking is large. Reduced; not only high processing efficiency, but also greatly improve the surface quality. The use of an electroless power source for wire-cut electrical discharge machining allows surface destructive layers to be controlled below 2 μm. The wear resistance of the cutting edge of the hard alloy die is no different from that of the grinding. It is even better than the mechanical grinding process. More and more parts are processed by "cutting and grinding". (3) Improvement of processing efficiency Due to the development of nanosecond pulse current source technology and detection, control, and anti-jamming technology, the processing efficiency of the slow-wire processing machine is also increasing. The highest processing efficiency of the current advanced wire processing machine is up to 500mm. 2/min. The processing efficiency of large-thickness workpieces is of practical significance. For example, when cutting 300 mm thick workpieces, the machining efficiency can reach 170 mm2/min. For the processing of workpieces with varying thickness, the thickness of the workpieces is automatically detected, and the processing parameters are automatically adjusted to prevent broken filaments and achieve the highest processing efficiency in this state. In addition, the advanced automatic threading machine introduces the automatic threading technology, automatic threading time <15 s to improve the efficiency of the processing operation; introduced dual wire automatic exchange technology, can use 0.20 ~ 0.02 mm wire electrode automatically double Wire switching processing. The first cutting is performed with coarse wire, the general wire diameter is 0.25 mm, to improve the processing efficiency, and can be cut without core; then the filament is used for trimming, generally 0.10 mm filaments are used to cut small round corners, and Improve the accuracy, the overall savings of 30% to 50% of the cutting time. (4) Development of Automation, Intelligence, and Informatization During the processing, in order to reduce human intervention and ensure that the desired process indicators are achieved, the automation, intelligence, and informationization of the slow wire processing have achieved corresponding development. The full process expert system of the slow-wire processing machine gives complete sets of parameters according to the processing requirements. Including not only common electrode wire number and corresponding workpiece materials, but also processing parameters such as PCD, PCBN and other special materials, depending on whether the upper and lower nozzles are in contact with the workpiece, how much the distance is, whether it is refined in the cutting wind, or open surface fine The optimization, precision, surface roughness, and efficiency of a preferred machining strategy to generate the respective criteria; the discharge expert system deals with the random factors in the cutting, cutting in, cutting out, section change, center cutting, near edge cutting, large In the case of high-speed cross-section cutting, adaptive control strategies and automatic control functions are used in the machining process to achieve stable and efficient wire processing. The automatic holeless detection function is also practical. In the case of automatic skip processing, if the pre-bored hole is forgotten or the hole position is offset, the machine will automatically move to the next pre-hole, which will prevent the machine from stopping when unmanned. When a short circuit occurs after threading, the position of the short circuit can be automatically searched to improve the reliability of continuous unattended operation. The CNC system of the machine tool is equipped with a standardized mechanical interface to form an intelligent manufacturing system. Through the robots of the 3R system or the EROWA system, the automatic exchange of workpieces (pallets) can be easily achieved, and expert systems and wire electrode automatic exchange technology can be used. Automatically complete the entire process. 2. The technical level of various grades of wire walking machine tools The machine can be divided into top grade, high grade, mid-range, and entry grades. The typical manufacturers of the slow-threading machine tools include Swiss GF Machining Solutions (formerly Agie Charmilles), Japanese Makino, Japanese Mitsubishi, Japanese Sodick, Western Japan, and Japanese Franks. (1) Top-level wire walking machine This kind of wire walking machine represents the highest level currently, mainly made in Switzerland and Japan. The machining accuracy of this type of machine tool can be guaranteed within ±0.002 mm, the maximum processing efficiency can reach 400-500mm2/min, the surface roughness can reach Ra0.05μm, and the machined surface quality is perfect. The surface has almost no deteriorating layer. The Φ0.02 mm electrode wire is used for micro-finishing. Most of the machines have a thermal balance system. Some machine tools are used for cutting in oil. This kind of machine tool has complete functions and high degree of automation. It can directly complete the precision machining of the mold. The life of the processed mold has reached the level of mechanical grinding. (2) High-grade walking wire processing machine This type of machine tool is basically produced by Swiss and Japanese companies. It has automatic threading function, no resistance electrolysis power supply, integrated thermal constant system, can use Φ0.07 mm wire to cut, the accuracy is about ± 0.003 mm, the highest processing The efficiency can reach 300mm2/min or more, and the surface roughness can reach Ra<0.2μm. It can timely detect the change of workpiece cross-section and optimize the discharge power function in real time. Such machine tools are also widely used for precision stamping die machining. (3) Mid-range wire moving machine This machine is generally produced by Swiss and Japanese companies in China's manufacturing plant. The technical level of some Taiwanese machines can also reach this level. Its configuration and performance meet the requirements of most of the domestic precision wire cutting processing. Generally use non-resistance anti-electrolysis power supply, with immersion water processing, taper cutting function. The practical maximum processing efficiency is 150～200 mm2/min, the best surface roughness is Ra<0.4μm, the cutting accuracy is up to ±0.005mm, generally the electrode wire with Φ0.1mm and above is used for cutting, equipped with Collision protection system can avoid collision damage caused by programming errors or misoperation, equipped with or optional automatic threading mechanism. (4) Entry Level Walking Wire Machine Tool This type of machine tool is usually a Taiwanese machine tool or a domestically-developed machine tool. Its configuration and performance meet the processing requirements of ordinary molds and parts in China. Generally use one more one to repair one, cut one to repair the two processes, can be stable to achieve a surface finish of Ra0.8μm, processing accuracy of ± 0.008mm, most can only use the electrode wire of 0.15mm and above to cut, the surface of the processing of fine organization There is a certain gap between the corner and the advanced machine tools. In general, compared with the wire processing machine, the walking wire processing machine has obvious advantages in processing efficiency, precision, and surface quality. Although the price of the wire spinning machine is relatively expensive, it will be increasingly used in various processing fields with the rapid development of the manufacturing industry. Taizhou Pinsum Furniture Co.,Ltd , https://www.pinsumchina.com
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