With the development of industrial production and the advancement of science and technology, more and more workpieces with various complex structures and special processes are required, which makes traditional mechanical processing methods impossible or difficult to process. Therefore, in addition to further developing and improving the mechanical processing method, people also strive to find new cnc machining methods. The EDM method can meet the needs of production development, and shows many excellent properties in the application. Therefore, it has been rapidly developed and increasingly widely used.
When the pulse voltage is applied between the two poles, the liquid medium closest to the poles at the time is broken down to form a discharge channel. Because the cross-sectional area of the channel is very small and the discharge time is extremely short, resulting in a high concentration of energy (106-107W / MM2), the high temperature generated in the discharge area causes the material to melt or even evaporate to form a small pit, as shown in Figure 1. After the discharge is over, after a short time interval, the second pulse is clicked through the discharge between poles recently. This cycle of high-frequency cycles continues, the tool electrode continues to feed the workpiece, and its shape is eventually copied on the workpiece to form the required machining surface.
Since the advent of EDM, many materials have been tried. According to the statistics of Suzhou Electro-Processing Machine Tool Research Institute, there are many kinds of electrode materials that can be used for EDM. Electrodes generally used for electrical discharge machining include copper, graphite, steel, and tungsten copper alloys.They can be used for electrical discharge machining of carbon steel, tool steel, alloy steel, hardened steel, cemented carbide and other high hardness metal materials. Machining stamping dies, cavity dies, and various parts and complex shaped surfaces. The properties of several commonly used electrode materials for EDM are shown in Table 1.
The electrode materials used in EDM are mainly copper machining and graphite, but there are certain problems. The graphite structure is loose, the particles are coarse, and the mechanical strength is poor. It is not easy to process into precise dimensions, and the graphite materials are generally of uneven quality, and the performance varies due to different particle orientations. Therefore, when graphite is used as a tool electrode, in order to process a workpiece with a smooth surface, the graphite material with a smaller particle diameter should be preferentially selected, and its microstructure and flexural strength should also be considered, especially when the electrode is made using the block method. Pay more attention to it, otherwise it will cause uneven loss of the electrode. Graphite electrodes are difficult to achieve the bright surface of the workpiece during finishing, and their productivity is very low. They can only be used to make some electrodes with complex shapes and low accuracy requirements.
In the finishing process, copper is used as the tool electrode for better processing results. However, due to the higher density of the copper material and the smaller inter-pulse value of the processing parameters, most of the eroded metal particles sink into the bottom of the working fluid tank, which increases the discharge. Difficulty of chips, resulting in an increase in the density of the working fluid and turbidity of the liquid, so that the machining surface is prone to "secondary discharge", arcing and burn phenomena, increased roughness of the workpiece, reduced processing stability, and greatly increased electrode wear. . Copper and copper alloy electrodes have large consumption, poor processing stability, and complex electrode shapes and high requirements for replication accuracy are not suitable today. Although the accuracy of silver-copper electrode processing is high, the production cost of silver-copper electrode is correspondingly high.
The use of tungsten copper alloy as the electrode can not only make the processed molds and parts with high precision, small electrode loss, high processing efficiency, but also complete the rough machining and finishing of the product in one time. With the increasing precision requirements of molds and the increasing use of many difficult-to-machine materials, the use of tungsten copper materials as electrodes for electrical discharge machining is also increasing. At present, tungsten copper electrode materials for electric discharge machining have become one of the main applications of tungsten copper materials. Statistics show that the amount of tungsten copper used for electrodes in Japan has reached the annual equivalent of 19.6T.
In order to make tungsten-copper alloys meet the characteristics of high electrical conductivity, can effectively remove metals, have small self-loss, and easy processing and molding, the requirements for tungsten-copper electrode materials specifically require that tungsten-copper materials have good electrical and thermal conductivity. It also has the best resistance to EDM corrosion. In order to ensure the stability in the EDM process and improve the utilization of electrode materials, tungsten copper materials are required to have high material uniformity and compactness, and it is difficult to meet the requirements with conventional electrical contact manufacturing methods.
EDM electrodes need to provide tungsten copper electrodes of corresponding shapes according to the requirements of the tool or product being processed. Some are slender rods, while others are complex-shaped profiles, which not only have various specifications and varieties, but also require smaller electrodes. Therefore, the preparation of the electrode is more complicated and difficult.
Tungsten Copper Electrode --- EDM
Electric discharge machining is also called electrical discharge machining. It is in the process of processing, which makes the pulse discharge spark between the tool and the workpiece constantly, relying on the local instantaneous high temperature generated during the discharge to remove the metal. The advantage of EDM is that it can process difficult-to-cut materials, very hard materials such as hard alloys, various high-speed steels and even diamonds, and cubic boron nitride. Another advantage is that it can process very delicate models. The principle of EDM is shown in Figure 1. During processing, one pole of the pulse power supply is connected to the tool electrode and the other pole is connected to the workpiece electrode. Both poles are immersed in liquid medium kerosene and mineral oil with a certain degree of insulation. The tool electrode is controlled by an automatic feed device to ensure that the tool and the workpiece maintain a small discharge gap (0.01-0.05mm) during normal processing.When the pulse voltage is applied between the two poles, the liquid medium closest to the poles at the time is broken down to form a discharge channel. Because the cross-sectional area of the channel is very small and the discharge time is extremely short, resulting in a high concentration of energy (106-107W / MM2), the high temperature generated in the discharge area causes the material to melt or even evaporate to form a small pit, as shown in Figure 1. After the discharge is over, after a short time interval, the second pulse is clicked through the discharge between poles recently. This cycle of high-frequency cycles continues, the tool electrode continues to feed the workpiece, and its shape is eventually copied on the workpiece to form the required machining surface.
Electrode materials commonly used in EDM
In the EDM process, the role of the electrode material is to transport processing pulses and to etch away the workpiece with its own minimum loss. It must meet the following conditions: 1. High conductivity. 2. Can effectively remove metals. 3. Small self-loss. 4. Easy to process. In actual processing, improper selection of electrode materials will accelerate electrode wear and affect processing quality and production efficiency.Since the advent of EDM, many materials have been tried. According to the statistics of Suzhou Electro-Processing Machine Tool Research Institute, there are many kinds of electrode materials that can be used for EDM. Electrodes generally used for electrical discharge machining include copper, graphite, steel, and tungsten copper alloys.They can be used for electrical discharge machining of carbon steel, tool steel, alloy steel, hardened steel, cemented carbide and other high hardness metal materials. Machining stamping dies, cavity dies, and various parts and complex shaped surfaces. The properties of several commonly used electrode materials for EDM are shown in Table 1.
The electrode materials used in EDM are mainly copper machining and graphite, but there are certain problems. The graphite structure is loose, the particles are coarse, and the mechanical strength is poor. It is not easy to process into precise dimensions, and the graphite materials are generally of uneven quality, and the performance varies due to different particle orientations. Therefore, when graphite is used as a tool electrode, in order to process a workpiece with a smooth surface, the graphite material with a smaller particle diameter should be preferentially selected, and its microstructure and flexural strength should also be considered, especially when the electrode is made using the block method. Pay more attention to it, otherwise it will cause uneven loss of the electrode. Graphite electrodes are difficult to achieve the bright surface of the workpiece during finishing, and their productivity is very low. They can only be used to make some electrodes with complex shapes and low accuracy requirements.
In the finishing process, copper is used as the tool electrode for better processing results. However, due to the higher density of the copper material and the smaller inter-pulse value of the processing parameters, most of the eroded metal particles sink into the bottom of the working fluid tank, which increases the discharge. Difficulty of chips, resulting in an increase in the density of the working fluid and turbidity of the liquid, so that the machining surface is prone to "secondary discharge", arcing and burn phenomena, increased roughness of the workpiece, reduced processing stability, and greatly increased electrode wear. . Copper and copper alloy electrodes have large consumption, poor processing stability, and complex electrode shapes and high requirements for replication accuracy are not suitable today. Although the accuracy of silver-copper electrode processing is high, the production cost of silver-copper electrode is correspondingly high.
Tungsten copper material for electrode
The use of tungsten copper alloy as the electrode can not only make the processed molds and parts with high precision, small electrode loss, high processing efficiency, but also complete the rough machining and finishing of the product in one time. With the increasing precision requirements of molds and the increasing use of many difficult-to-machine materials, the use of tungsten copper materials as electrodes for electrical discharge machining is also increasing. At present, tungsten copper electrode materials for electric discharge machining have become one of the main applications of tungsten copper materials. Statistics show that the amount of tungsten copper used for electrodes in Japan has reached the annual equivalent of 19.6T.
In order to make tungsten-copper alloys meet the characteristics of high electrical conductivity, can effectively remove metals, have small self-loss, and easy processing and molding, the requirements for tungsten-copper electrode materials specifically require that tungsten-copper materials have good electrical and thermal conductivity. It also has the best resistance to EDM corrosion. In order to ensure the stability in the EDM process and improve the utilization of electrode materials, tungsten copper materials are required to have high material uniformity and compactness, and it is difficult to meet the requirements with conventional electrical contact manufacturing methods.
EDM electrodes need to provide tungsten copper electrodes of corresponding shapes according to the requirements of the tool or product being processed. Some are slender rods, while others are complex-shaped profiles, which not only have various specifications and varieties, but also require smaller electrodes. Therefore, the preparation of the electrode is more complicated and difficult.