Free positive ions and electrons accumulate in the field and quickly form an ionized conductive channel. At this stage, a current is formed between the two plates. Resulting in countless collisions between the particles, forming a plasma zone, which quickly rises to a high temperature of 8000 to 12000 degrees, instantaneously melting some materials on the surfaces of the two conductors, and at the same time, due to the vaporization of the electrode and the dielectric fluid, a bubble is formed. And its pressure rises regularly until it is very high. Then the current is interrupted and the temperature suddenly drops, causing the bubbles to explode inwardly. The generated power throws the melted material into the crater, and then the corroded material recondenses into a small sphere in the dielectric fluid and is discharged by the dielectric fluid. Then through the monitoring and control of NC control, the servo mechanism executes to make this discharge phenomenon uniform.
Wire Electrical Discharge Machining is abbreviated as WEDM, which belongs to the category of electrical machining. When the former Soviet Union Lazarenko and his wife studied the phenomenon and causes of switch contacts damaged by spark discharge, they found that the instantaneous high temperature of electric sparks can melt and oxidize local metals. It was corroded away, thus pioneering and inventing the EDM method. The wire cutting machine was also invented in the former Soviet Union in 1960, and China was the first country to be used in industrial production.
The Classification Of Wire Cutting
Wire EDM can be divided into Reciprocating type High Speed Wire cut Electrical Discharge Machining, Low Speed one-way walk Wire cut Electrical Discharge Machining and Vertical Wire Electrical Discharge Machining machine tool With Rotation Wire according to the wire speed. It can also be divided into single column cross table type and double column type (commonly known as gantry type) according to the table form.
Reciprocating wire EDM wire cutting machine
The reciprocating wire EDM wire cutting machine has a fixed wire speed of 6-12 mm/s, which is a unique machine type in China. Since September 1970, the State-owned Changfeng Machinery General Factory affiliated to the Third Ministry of Machinery Industry has successfully developed the “Digital Program Automatic Control Wire Cutting Machine Tool”, which is the domestic first of this type of machine tool. In 1972, the Third Ministry of Machinery Industry conducted a technical appraisal of the CKX CNC wire-cutting machine produced in the factory, and believed that it had reached the domestic advanced level at that time. In 1973, in accordance with the decision of the Third Ministry of Machinery Industry, the CNC wire-cutting machine tool numbered CKX-1 was put into mass production. In September 1981, the DK3220 coordinate numerical control machine with taper cutting function was successfully developed. The biggest feature of the product is the 1.5-degree taper cutting function. Completed the major technical improvement of the wire cutting machine tool. With the gradual improvement of the large taper cutting technology, great progress has been made in the cutting of variable taper and upper and lower profile. With the breakthrough of large-thickness cutting technology, the accuracy of cross-section and longitudinal section has been greatly improved, and the processing thickness can exceed 1000mm. The reciprocating wire cutting machine has certain advantages. At the same time, it meets the needs of customers at home and abroad. The number of such machine tools is increasing at a relatively rapid rate, from the original annual output of 2 to 3,000 units to tens of thousands of units per year. The national stock of reciprocating wire-cutting machine tools has reached more than 200,000 units, which are used in various types of machines. Low-end mold manufacturing and special parts processing have become one of the most widely used types of CNC machine tools in China. However, since the reciprocating wire cutting machine tool cannot implement constant tension control on the electrode wire, the electrode wire shakes a lot, and the wire breaks easily during the processing. Since the electrical grade wire is used reciprocatingly, it will cause the loss of the electrode wire and reduce the processing accuracy and surface quality.
Low-speed one-way wire EDM wire cutting machine
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 0.2mm/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. 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 it adopts non-resistance anti-electrolysis power supply, generally with automatic wire threading and constant tension device. 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 EDMs manufactured by Taiwanese enterprises should belong to the range of mid-range machines. In the past 3 years, they will reach an annual growth rate of 20% to 30%. It is estimated that in the next 5 years, Taiwan’s low-speed wire EDMs The output can reach 2000 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, Chinese scientific and technological workers have invested a large amount of research and development forces. They have completed the research and development of a new generation of low-speed wire EDM wire cutting machines, and have made major breakthroughs. Products, and occupy a certain market share, its performance indicators can reach the level of mid-range machines. Some domestic companies hope to develop low-speed wire EDM wire cutting technology through cooperation with related Taiwanese companies.
Vertical self-rotating wire EDM
Vertical self-rotating wire electric discharge machine (horizontal self-rotating wire electric discharge machine). The characteristics of the vertical rotary wire EDM are different from the traditional high-speed wire and low-speed wire EDM. First of all, the movement of the electrode wire is one more electrode than the traditional two types of wire EDM. Rotary movement of the wire; secondly, the wire speed of the electrode wire is between high-speed wire and low-speed wire, and the speed is 1 to 2 mm/s. Due to the increase of the rotating movement of the electrode wire during the machining process, the biggest difference between the vertical revolving EDM wire cutting machine and other types of wire cutting machines is the wire feeding system. The wire feeding system of the vertical rotary EDM wire cutting machine consists of two sets of the wire feeding end and the wire feeding end as the wire feeding structure, which realizes the compound movement of the high-speed rotating movement of the electrode wire and the low-speed wire feeding. The area between the two sets of spindle heads is the effective processing area. Except for the wire feeding system, the other components of the machine tool are the same as the high-speed wire cutting machine.
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 “medium 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 8-12mm/s high-speed wire during rough machining and use in fine machining. 1-3mm/s low-speed wire travel, 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 compared with 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 on the X and Y coordinate tables. At the same time, they have adopted the full closed loop control with pitch compensation function, and the CNC system can be used. Compensate and correct 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. The “medium wire machine” has the characteristics of simple structure, low cost and low consumption, so it also has its living space. The implementation standard is still the relevant standard of high-speed wire machine. Therefore, manufacturers should pay attention to the publicity of users. , We must seek truth from facts.
Wire EDM Classification
Distinguish between fast-moving wire cutting, middle-moving wire cutting, and slow-moving wire cutting.
- 1: The wire speed of fast wire EDM wire cutting is 6-12 mm/s, and the electrode wire moves back and forth at high speed, so the cutting accuracy is poor.
- 2: Middle wire EDM wire cutting is based on fast wire wire cutting to realize the function of frequency conversion multiple cutting. It is a new technology developed in recent years.
- 3: The wire speed of slow wire EDM wire cutting is 0.2mm/s, and the electrode wire moves in one direction at a low speed, so the cutting accuracy is very high.