normal power graphite electrode

Application of normal power graphite electrode EDM in mold manufacturing

EDM characteristics of graphite materials

(1) Electric discharge machining speed Graphite is a non-metallic material with a very high melting point of 3650 ℃, while the melting point of copper is 1083 ℃, so the normal power graphite electrode can withstand larger current setting conditions. When the discharge area and the size of the normal power graphite electrode scale larger, the superiority of the graphite material’s high-efficiency rough machining is more obvious. The thermal conductivity of graphite is 1/3 of that of copper, and the heat generated during the discharge process can be used to remove metal materials more effectively. Therefore, its processing efficiency is higher than that of copper normal power graphite electrode in medium and fine processing. According to machining experience, under the correct conditions of use, the electrical discharge machining speed of the normal power graphite electrode is 1.5~2 times faster than the copper normal power graphite electrode as a whole.

(2) The loss of normal power graphite electrode The normal power graphite electrode has the characteristics of being able to withstand high current conditions. In addition, under the appropriate roughing setting conditions, the erosion and working fluid produced during the processing of carbon-containing steel workpieces The carbon particles in the decomposition products produced at high temperature will adhere to the surface of the normal power graphite electrode to form a protective layer under the effect of the polarity effect, which ensures that the normal power graphite electrode is thick The loss in processing is extremely small, even “zero loss”. The main loss of normal power graphite electrode in EDM comes from rough machining. Although the loss rate of finishing setting conditions is high, because the reserved machining allowance of parts is not much, the amount of machining erosion is small, and the overall loss is Also less. In general, the loss of the normal power graphite electrode in the rough machining of high current is less than that of the copper normal power graphite electrode, and the loss in the finishing process may be slightly larger than that of the copper normal power graphite electrode. The loss of the normal power graphite electrode of the two is equivalent. .

(3) Surface quality The particle diameter of graphite material directly affects the surface roughness of EDM, the smaller the diameter, the lower the surface roughness value can be obtained. A few years ago, graphite materials with a particle diameter of φ5 μm were used, and the best surface for EDM can only reach VDI18 (Ra0.8 μm). Nowadays, the particle diameter of graphite materials can reach within φ3 μm, which is the best surface for EDM. It can stably reach VDI12 (Ra0.4 μm) or a finer level, but the normal power graphite electrode cannot be used for mirror EDM. The resistivity of copper material is low, and the structure is dense. EDM is easy to obtain a stable processing state, and it can be processed stably under difficult conditions. The surface roughness can be less than Ra0.1 μm, and it can be mirrored EDM. . It can be seen that if the electrical discharge machining pursues an extremely fine surface, it is more appropriate to use copper materials to make the normal power graphite electrode. This is the main advantage of the copper normal power graphite electrode over the normal power graphite electrode. However, under the condition of high current setting, the surface of the normal power graphite electrode is prone to become rough and even cracks, while graphite materials do not have this problem. The surface roughness requirement is VDI26 (Ra2.0 μm) For cavity processing, one normal power graphite electrode can be used to complete the machining process from coarse to fine, achieving a uniform texture effect and no defects on the surface. In addition, due to the difference in the structure of graphite and copper, the corrosion points of the surface discharge of the normal power graphite electrode are more regular than that of the copper normal power graphite electrode. Therefore, when processing the same surface roughness of VDI20 and above, use the workpiece processed by the normal power graphite electrode The surface granularity is more distinct, and the texture effect is better than the discharge surface effect of the copper normal power graphite electrode.

(4) Machining accuracy The thermal expansion coefficient of graphite materials is small, and the thermal expansion coefficient of copper materials is 4 times that of graphite materials. Therefore, the normal power graphite electrode is less susceptible to deformation in electrical discharge machining than the copper normal power graphite electrode, and more stable and reliable Precision. Especially when processing deep and narrow ribs, local high temperature will easily cause the copper normal power graphite electrode to bend and deform, but the normal power graphite electrode will not be like this; for the copper normal power graphite electrode with a large depth-to-diameter ratio, it is It is also necessary to compensate a certain thermal expansion value to correct the size, which is not required for the normal power graphite electrode.

(5) The weight of the normal power graphite electrode Graphite material is smaller than the density of copper, and the weight of the normal power graphite electrode of the same volume is only 1/5 of that of the copper normal power graphite electrode. It can be seen that the larger normal power graphite electrode using graphite material is very suitable, which greatly reduces the load on the spindle of the EDM machine tool. The normal power graphite electrode will not cause problems such as inconvenience in clamping and yaw displacement during processing due to its heavy weight. It can be seen that it is very meaningful to use normal power graphite electrode in large mold processing.

(6) Difficulty in making normal power graphite electrode Graphite material has good machining performance, and the cutting resistance is only 1/4 of copper. Under the correct processing conditions, the efficiency of milling normal power graphite electrode is 2 times that of copper normal power graphite electrode. ~3 times. The normal power graphite electrode is easy to clean the corners, and the workpiece that is usually completed by multiple normal power graphite electrodes can be designed into a whole normal power graphite electrode for processing. The unique particle structure of the graphite material makes the normal power graphite electrode not produce burrs after milling and molding. It directly meets the requirements for complex shapes that are inconvenient to remove the burrs, eliminating the need for manual polishing of the normal power graphite electrode. The shape changes and dimensional errors caused by polishing are eliminated. It should be noted that because graphite is a dust accumulation, a large amount of dust will be generated when milling graphite, so the milling machine must have a sealing and dust suction device. If you need to use EDM wire cutting to process the normal power graphite electrode, its processing performance is not as good as that of copper materials, and the cutting speed is about 40% slower than that of copper.

(7) The installation of normal power graphite electrode and the use of graphite materials have good adhesion. Conductive glue can be used to bond graphite to fixtures for milling normal power graphite electrode and electric discharge machining, which can be omitted on the normal power graphite electrode material. The process of machining screw holes saves working time. Graphite materials are relatively brittle, especially the small, narrow and long normal power graphite electrode, which is easy to break when subjected to external force during use, but it can be immediately known that the normal power graphite electrode is damaged. If it is a copper normal power graphite electrode, it will only bend and not break. This situation is very dangerous and difficult to find during use, and it is easy to cause the workpiece to be scrapped.

(8) Prices In recent years, the price of copper materials has continued to rise, and major graphite manufacturers continue to improve the process of making graphite to make it more cost-effective. Under the same volume, the price of the universal normal power graphite electrode material is equivalent to that of the copper normal power graphite electrode material, while the price of fine graphite will be higher than that of the copper normal power graphite electrode. In summary, among the eight EDM characteristics of normal power graphite electrode, its advantages are obvious: the efficiency of milling normal power graphite electrode and electric discharge machining is significantly better than that of copper normal power graphite electrode, and the weight of large normal power graphite electrode is small. , The dimensional stability is good, the sheet normal power graphite electrode is not prone to deformation, the surface texture is better than copper, and the price is lower. The disadvantage of graphite material is that it is not suitable for fine surface electrical discharge machining below VDI12 (Ra0.4 μm), and the efficiency of using EDM to make normal power graphite electrode is low. But from a practical point of view, an important reason that affects the effective promotion of graphite materials in China is that milling of normal power graphite electrode requires a special graphite processing machine, which puts new requirements on the processing equipment of mold companies, and some small companies May not have this condition. In general, the advantages of the characteristics of the normal power graphite electrode cover most of the machining occasions of EDM, and it is worthy of promotion and application. The long-term benefits are considerable. The shortcomings of its fine surface processing can be compensated by using the copper normal power graphite electrode. When the carbon company was founded, it established the development strategy of “science and technology, innovation, and leadership”, adhering to the business philosophy of “quality first, service first”, through technological improvement, quality improvement, and market development, carbon has become a region in Shanxi, Hebei, and Mongolia. The largest graphitization processing company. The main business includes normal power graphite electrode, Shijiazhuang normal power graphite electrode, Datong silicon carbide, carbon normal power graphite electrode processing.