Application of graphite materials in spark machini

2022-10-19
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Many users in the field of EDM still have many doubts about the application of graphite electrode materials. On the one hand, the long-term use of traditional copper makes users have psychological habits and dependence on it, on the other hand, it is due to their lack of practical application experience of milling machine or EDM

in the 1960s, copper was widely used as an electrode material, accounting for about 90%, while graphite accounted for only about 10%. But today, this situation has changed. In Europe, more than 90% of electrode materials are graphite. Copper, once the dominant electrode material, has almost lost its advantages over graphite electrode. What caused this dramatic change? EDM industry in recent years can prove that this change is due to many advantages of graphite electrode

this article will explain some problems that may be encountered when using graphite materials in EDM. We hope that this article can dispel your doubts about graphite materials

1 is graphite material dangerous

the graphite used in EDM is synthetic rather than natural graphite. Synthetic graphite must be manufactured and formed through a long high-tech production process without radiation!. According to different product specifications, the generation process generally takes four to seven months. In the production process, graphite should be processed at a high temperature of up to 3000 degrees Celsius. Such a high temperature makes most of the impurities volatilize, so that the purity of graphite is as high as 99.99% (100ppm). This means that there are only 100 impurities in onemillion products, and these impurities are decomposed into various elements, which are difficult to be found. The purity of graphite required for some special applications can even be less than 5ppm. Therefore, there are few cases where pure natural raw materials are completely used in product manufacturing and mold manufacturing

for employees who operate milling machines, working in a dusty environment is indeed a danger. If this tiny dust is inhaled into the lungs, it will cause damage to the respiratory tract. Therefore, the tightness of the machine is very important. Nowadays, high-speed milling machines used for graphite processing are equipped with sealing devices and dust collectors, which are standard configurations of machine tools. As long as they are properly maintained, there is no need to worry about the harm caused by dust

2 will the rib break during processing

according to relevant tests, it is found that if incorrect or unreasonable cutting methods, cutting parameters and cutting tools that are not suitable for graphite processing are used, rib fracture will often be caused

from the perspective of processing technology, graphite cannot be compared with copper, because it completely adopts different processing technology. For example, the larger the feed rate of each tool, the smaller the tool wear. In addition, contrary to metal material processing, in graphite processing, with the increase of cutting speed, tool wear decreases significantly

in this case, we mainly use diamond or diamond coated tools. While using, people also need to pay attention to many rules that are completely different from metal material processing. Usually, when an enterprise introduces every new process such as software, machine control system and automation system, it will generally train its employees. But only when the copper processing method is converted into graphite processing, enterprises rarely provide them with training opportunities. Therefore, many manufacturers who used graphite to replace copper for EDM, this early attempt has been aborted from the beginning

3 spend more time learning applications

it usually takes time to accept new things. People must think about how to treat the topic of relatively new graphite materials in a different way, and may also need to redesign some processes in the processing process to cooperate. But more importantly, taking these measures can not only bring us huge cost savings, but also greatly shorten the mold manufacturing cycle - the EDM efficiency with graphite electrode is times that of copper, and the cutting efficiency is times that of copper

from the perspective of the global market, if someone can still continue to operate in the European production mode 20 years ago, and succeed in winning a place in the competition with Asia and Eastern Europe, his products must be very unique. Otherwise, if the old production process is not improved, it will inevitably be overtaken by others. Graphite is such an excellent electrode material that can make people's desire to quickly reduce costs possible

many users have reduced the number of electrodes by more than half after adopting graphite materials. What results will this produce

⑴ electrode clamps required for electrode clamping are greatly reduced

⑵ the number of electrodes to be installed is reduced

⑶ only a small amount of zero setting is required

⑷ the workload of electrode measurement is greatly reduced

(5) the amount of materials used to make electrodes is greatly reduced

⑥ the cutting cycle is significantly shortened, and the electrode loss is correspondingly reduced. When using copper electrodes, one cavity needs more electrodes. If graphite is used, the previous electrodes can be combined into one electrode. In this way, the current that the electrode can pass through increases, which not only improves the processing efficiency, but also reduces the electrode loss

⑺ the cutting speed is significantly higher than that of copper material

4. Is copper material more economical than graphite material

this general statement has no factual basis, because people often ignore the fact that they have different measurement methods. Copper is measured in kilograms, while graphite is usually measured by volume. In the process of conversion, people should also consider electricity. If the displacement system is found to have a fault, we must deal with the situation of various densities of polar materials in time. Recently, the price of copper in the international market has risen sharply to about 60 yuan per kilogram (at the beginning of 2005, the price of copper was only about 30 yuan per kilogram), the price of graphite material itself has been relatively lower than that of copper, and copper is a non renewable resource, so the price will only become more and more expensive. If someone wants to buy 1 cubic decimeter (about 9 kilograms) of copper now, he has to pay about 540 yuan. At this price, people have been able to obtain relatively high-quality graphite products, and the price of ordinary brand graphite is even lower. In the calculation of cost optimization, the price of graphite and copper is certainly an element, but efficiency and product quality are more important. The characteristics of graphite materials mentioned above and the role they can play in application are the key. The specific situation will be mentioned later

5 is graphite prone to rib fracture during storage or transportation

this statement is certainly correct, but is this phenomenon necessarily a deficiency? If the ribbed electrode breaks due to improper handling during transportation, people will immediately find out this situation and immediately know that the electrode is damaged. If copper is used, the ribs will bend after improper treatment. Whether people can find this defect immediately is very doubtful. If it is not found in time and people continue to use this electrode for EDM, the damage of the cavity or workpiece is inevitable

if the rib of a graphite electrode breaks, people can decide whether to mill a new electrode according to the specific situation. When the electrode price is high, you can also connect (stick) a section of graphite, then mill this section again, and use the broken section to make a single electrode again

6 can the processed surface quality meet the standard of copper

a few years ago, people may also think that the surface quality of parts processed with graphite can only reach vdi18. However, it has been shown that the surface quality of the workpiece processed with graphite material can reach vdi12 or higher. Of course, this standard is not applicable to all graphite materials or traditional EDM machine tools, such as crude graphite or conventional graphite, which cannot meet this standard. To obtain such surface quality, various production conditions must be in the best fit with graphite materials. In this case, the size of electrode, process and the choice of graphite type are the key factors, which will play a decisive role. However, the important point is that the use of graphite materials can achieve very fine surface quality

many manufacturers of EDM equipment and graphite materials have made a lot of efforts. Today, they can provide customers with specific processing equipment and processing parameters for graphite processing. Moreover, graphite manufacturers also rely on their more refined graphite brands to meet the needs of customers

however, the most important factor is that people must choose equipment manufacturers and graphite manufacturers. Making a mountain out of a molehill often happens. For example, some customers will select the most complex parts for sample processing, and then go to the equipment manufacturer for testing and processing. In fact, such components account for up to 1% of the customer's product categories. If the equipment and process are based on this standard, there is no doubt that there will be a problem: what about 99% of other conventional processing

therefore, the equipment usually selected should meet 95% of the product types. Other types of products can be entrusted to other enterprises that are good at special processing, or a repeatedly used electrode can be selected. In this case, we can also extend the discharge time or apply copper electrode if necessary

7 can graphite adopt the same lower deviation as copper

theoretically, the answer is yes. However, we do not recommend it. Due to the specific thermal properties of copper, the lower deviation can usually be selected. Graphite can withstand higher energy, so a larger lower deviation should be adopted. The relative loss is also significantly reduced. Because people can mill very small fins with graphite, the possibility of selecting large lower deviation can also be realized

8 is the loss increased when graphite is processed

this may be a problem. However, customers often mention that this "safe size" can still meet customers' requirements after discharge. Generally, the phenomenon of increased loss of graphite materials often occurs when processing small electrodes; And people will habitually repair materials directly after processing. In fact, this practice is wrong. After EDM, there is also a polishing process of bolts, screws and bolts gb/t3098.1 (2) 000, which generally does not take a long time

there is another problem that needs to be paid attention to: if there is always an allowance of 0.01 to 0.02 mm for parts, can we add electrode compensation during programming, so that the inspection data can be added at one time to deviate from the work position, without the need for follow-up processing

9 is wire cutting slower than copper

this view is correct. Because the melting point of graphite is much higher than that of copper, it is more difficult to process. However, it should be noted that most relevant industries, such as graphite manufacturers, equipment manufacturers and production line manufacturers, have long begun to solve this problem. People can use the latest equipment (such as laser processing, high-pressure water jet) to process qualified products, including xarelto, eylea, stivarga, xofigo and ademp

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