Compared with copper electrodes, graphite electrodes have the advantages of low electrode consumption, fast processing speed, good machining performance, high processing accuracy, small thermal deformation, light weight, easy surface treatment, high temperature resistance, high processing temperature, and electrodes can be bonded. Although graphite is a very easy-to-cut material, due to the fact that the graphite material (hot work die steel) used as an EDM electrode must have sufficient strength to avoid damage during handling and EDM processing, while the electrode shape (thin-wall, small Rounded corners, sharp changes), etc. also put higher requirements on the grain size and strength of the graphite electrode, which leads to the easy collapse of the graphite workpiece and the easy wear of the tool during the processing.

Tool wear is the most important problem in graphite electrode machining. The wear amount not only affects the cost of tool wear, processing time, and processing quality, but also affects the surface quality of the workpiece material processed by the electrode EDM, which is an important parameter for optimizing high-speed processing. ． The main tool wear areas for graphite gun electrode material processing are the rake face and the flank face. On the rake face, the impact contact between the tool and the broken chip area produces impact abrasive wear, and the chips sliding along the tool surface produce sliding friction wear. Several factors that affect tool wear are as follows.

(1) Tool material The tool material (mold steel) is the fundamental factor that determines the cutting performance of the tool, which has a great influence on the processing efficiency, processing quality, processing cost and tool durability. The harder the tool material, the better its wear resistance, the higher the hardness, the lower the impact toughness, and the more brittle the material is. For graphite tools, the ordinary TiAIN coating can be appropriately selected with relatively good toughness, that is, the cobalt content is slightly higher; for the diamond-coated graphite tool, the hardness is relatively good, that is, the cobalt content can be selected. slightly lower.

(2) Geometric angle of the tool Selecting the appropriate geometric angle for the graphite tool helps to reduce the vibration of the tool, and conversely, the graphite workpiece is not easy to chip;

① Front angle. When machining graphite with negative rake angle, JJ has better edge strength, good impact resistance and friction performance. When machining with a positive rake angle, as the rake angle increases, the strength of the tool edge is weakened, which leads to increased flank wear. When machining with a negative rake angle, the cutting resistance is large, which increases the cutting vibration. When machining with a large positive rake angle, the tool wear is serious and the cutting vibration is also large.

② rear corner. If the clearance angle increases, the edge strength of the tool decreases, and the wear area of the flank face gradually increases. When the tool clearance angle is too large, the cutting vibration is strengthened.

③ Helix angle. When the helix angle is small, the cutting edge length of the graphite workpiece on the same cutting edge is the longest, the cutting resistance is greater, and the cutting impact force on the tool is greater, so the tool wear, milling force and cutting vibration are greater. When the helix angle is large, the direction of the milling resultant force deviates from the surface of the workpiece to a greater extent, and the cutting impact caused by the collapse of the graphite material intensifies, so the tool wear, milling force and cutting vibration also increase.

Therefore, the influence of tool angle change on tool wear, milling force and cutting vibration is caused by the combination of rake angle, clearance angle and helix angle, so you must pay more attention when selecting. Through extensive scientific testing of the machining characteristics of graphite materials, PARA tools optimize the geometry of the relevant tools, thereby greatly improving the overall cutting performance of the tools.

(3) The coating of the tool Diamond-coated tool has the advantages of high hardness, good wear resistance and low friction factor. At this stage, diamond coating is a better choice for graphite machining tools, and it can best reflect the superior performance of graphite tools. ; The advantage of diamond-coated cemented carbide cutting tools is that it combines the hardness of natural diamond with the strength and fracture toughness of cemented carbide; but the domestic diamond coating technology is still in its infancy, and the cost of investment is very large. , so the diamond coating will not have much development in the near future, but we can optimize the angle of the tool, material selection and other aspects and improve the structure of the ordinary coating on the basis of ordinary tools, to a certain extent, it can be processed in graphite applied in.

      There is an essential difference between the geometric angles of diamond-coated tools and ordinary coated tools. Therefore, when designing diamond-coated tools, due to the particularity of graphite processing, the geometric angle can be appropriately enlarged, and the cutting grooves can also be enlarged, which will not Reduce the wear resistance of the cutting edge of the tool; for the ordinary TiAIN coating, although the wear resistance of the uncoated tool is significantly improved, compared with the diamond coating, its geometric angle should be appropriate when machining graphite Put it small to increase its wear resistance. For diamond coating, many coating companies in the world have invested a lot of manpower and material resources to research and develop related coating technologies, but so far, foreign mature and economical coating companies are limited to Europe; This model of graphite machining tool also uses the most advanced coating technology in the world to carry out surface treatment on the tool to ensure the machining life and at the same time ensure the economical and practicality of the tool.

(4) Reinforcement of tool edge The passivation technology of tool edge is a very important issue that has not been widely valued by people. The edge of the carbide tool sharpened by the diamond grinding wheel has microscopic gaps (ie, micro chipping and sawing) of different degrees. Graphite high-speed cutting puts forward higher requirements on tool performance and stability, especially for diamond-coated tools, which must be passivated before coating to ensure the firmness and service life of the coating. The purpose of tool passivation is to solve the above-mentioned defects of the microscopic notch of the knife edge after sharpening, reduce or eliminate the edge value, and achieve the purpose of being smooth and smooth, both sharp, strong and durable.