The main factors that affect CNC tool wear include:

1. Tool geometry angle

Selecting the appropriate geometric angle of the special milling cutter for graphite helps to reduce the vibration of the tool, and conversely, the graphite workpiece is not easy to chip. 2. Tool material

The tool material 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. Hardness and toughness are a pair of contradictions, and it is also a key problem that tool materials should solve. For graphite tools, ordinary tialn coatings can be appropriately selected with relatively good toughness, that is, with a slightly higher cobalt content; for diamond-coated graphite tools, a relatively high hardness can be appropriately selected in material selection, and It is slightly lower in cobalt content.

2.1 Front angle

When machining graphite with negative rake angle, the cutting edge strength of the tool is good, and the performance of impact resistance and friction is good. 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.

2.2 Rear angle

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.

2.3 Helix angle

When the helix angle is small, the blade length of the graphite workpiece on the same cutting edge is the longest, the cutting resistance is the largest, and the cutting impact force on the tool is the largest, so the tool wear, milling force and cutting vibration are the largest. When the helix angle is large, the direction of the milling resultant force deviates from the workpiece surface to a large extent, and the cutting impact caused by the chipping 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 generated by the combination of rake angle, clearance angle and helix angle, so you must pay more attention when selecting.

3. Tool coating

Diamond-coated end mills have the advantages of high hardness, good wear resistance, and low friction coefficient. At this stage, diamond coating is the best choice for graphite machining tools, and it can also reflect the superior performance of graphite tools. The advantages of diamond-coated cemented carbide cutting tools are: combining the hardness of natural diamond with the strength and fracture toughness of cemented carbide.

However, at present in China, the diamond coating technology is still in its infancy, and the cost is also very large, so the diamond coating will not have much development in the near future. However, we can optimize the angle of the tool, select the material and improve the structure of the ordinary coating on the basis of the ordinary tool, and to a certain extent, it can still be applied in the graphite processing.

The geometric angle of diamond-coated tools is essentially different from that of 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 chip flute will also be enlarged, without Reduce the wear resistance of the cutting edge of the tool. For ordinary tialn coating, although its wear resistance is significantly improved compared with uncoated tools, compared with diamond coating, its geometric angle should be appropriately reduced when machining graphite to increase its wear resistance. sex.

For diamond coating, many coating companies in the world have invested a lot of manpower and material resources to research and develop related technologies, but so far, foreign coating companies with mature technology and good economy are limited to European companies.

4. Tool edge strengthening

The passivation of the tool edge is a very important problem that has not been generally paid attention to by people. The cutting edge of the cemented carbide tool sharpened with a diamond grinding wheel has microscopic gaps (ie, micro chipping and saw teeth) of different degrees.

High-speed cutting of graphite puts forward higher requirements for tool performance and stability, especially 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 problem of the microscopic gap of the cutting edge after the tool is sharpened, reduce its sharpness, and achieve the purpose of smoothness and smoothness, which is strong and durable.

5. Cutting conditions

The choice of cutting conditions has a considerable impact on tool life.

5.1 Cutting method (climb milling and up milling)

The cutting vibration of down milling is smaller than that of up milling. During climb milling, the cutting thickness of the tool is reduced from Z to zero. After the tool cuts into the workpiece, there will be no bouncing knife phenomenon caused by the inability to cut chips. The rigidity of the process system is good and the cutting vibration is small. The thickness increases from zero to Z. In the initial stage of cutting, due to the thin cutting thickness, a path will be scratched on the surface of the workpiece. At this time, if the cutting edge encounters hard points in the graphite material or chip particles remaining on the surface of the workpiece, All will cause the tool to bounce or chatter, so the cutting vibration of up-cut milling is large.

5.2 Blowing (or vacuuming) and immersing EDM fluid processing

Timely cleaning of the graphite dust on the surface of the workpiece is conducive to reducing the secondary wear of the tool, prolonging the service life of the tool, and reducing the impact of graphite dust on the machine tool lead screw and guide rail.

Tool wear is the most important problem in graphite electrode machining. The amount of wear 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 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.