The tool is hard, and the tool will have some wear and tear with the delay of the use time. What are the reasons for the tool wear? There are several reasons for this by summarizing.
1, tool materials
Tool material is the fundamental factor determining the cutting performance of the tool, and has a great influence on machining efficiency, machining quality, machining cost and tool durability.
The harder the tool material is, the better its wear resistance is. The higher the hardness, the lower the impact toughness and the brittle material. Hardness and toughness are a pair of contradictions and a key to the tool material. For graphite cutters, the ordinary tialn coating can be selected to have a relatively better toughness in the selection of materials, that is, the cobalt content is slightly higher; for diamond-coated graphite cutters, the hardness can be appropriately selected on the material selection. , that is, the cobalt content is slightly lower;
2, the geometric angle of the tool
The choice of the appropriate geometric angle of the graphite tool helps to reduce the vibration of the tool, and in turn, the graphite workpiece is not easily broken;
(1) The rake angle, when the graphite is processed by the negative rake angle, the cutting edge strength is good, and the impact resistance and friction performance are good. As the absolute value of the negative rake angle decreases, the flank wear area does not change much, but The overall trend is decreasing. When the positive rake angle is used, the tool edge strength is weakened as the rake angle increases, which in turn leads to increased wear on the flank. When the negative rake angle is processed, the cutting resistance is large, and the cutting vibration is increased. When the large positive rake angle is used, the tool wear is severe and the cutting vibration is large.
(2) Back angle, if the back angle increases, the tool edge strength decreases, and the flank wear area gradually increases. When the back angle of the tool is too large, the cutting vibration is strengthened.
(3) When the helix angle is small, the blade length of the graphite workpiece is the longest at the same cutting edge, the cutting resistance is the largest, and the cutting impact force of 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 force is larger than the surface of the workpiece, and the cutting impact caused by the collapse of the graphite material is intensified, so that the tool wear, the milling force and the cutting vibration are also increased. Therefore, the influence of tool angle change on tool wear, milling force and cutting vibration is the combination of front angle, back angle and spiral angle, so we must pay more attention to the selection.
Through a large number of scientific tests on the processing characteristics of graphite materials, para tools optimize the geometric angle of the relevant tools, so that the overall cutting performance of the tool is greatly improved.
3, the coating of the tool
Diamond coated tools have the advantages of high hardness, good wear resistance and low friction coefficient. At present, diamond coating is the best choice for graphite processing tools, and it also best reflects the superior performance of graphite tools; hard coating of diamond coating The advantages of alloy cutters are the combination of the hardness of natural diamonds and the strength and fracture toughness of cemented carbides. However, in domestic diamond coating technology is still in its infancy, and the cost investment is very large, so diamond coatings in the near future There won't be much development, but we can optimize the angle of the tool, select materials and improve the structure of the ordinary coating on the basis of ordinary tools, and it can be applied to graphite processing to some extent.
There is a fundamental difference between the geometric angle of the diamond coated tool and the ordinary coated tool. Therefore, when designing the diamond coated tool, due to the particularity of graphite processing, the geometric angle can be appropriately enlarged, and the groove can be enlarged. Reduces the wear resistance of the tool front; for ordinary tialn coatings, although the wear resistance is significantly improved compared to uncoated tools, it is geometrical when machining graphite compared to diamond coatings. It should be appropriately small to increase its wear resistance.
For diamond coatings, many coating companies in the world have invested a lot of manpower and material resources to research and develop related coating technology, but so far, foreign mature and economical coating companies are limited to Europe; para as a The excellent graphite processing tool also uses the world's most advanced coating technology to surface the tool to ensure the processing life and ensure the economical and practical tool.
4, the reinforcement of the cutting edge
Tool edge passivation technology is a problem that has not been widely recognized and is very important. The edge of the carbide cutter after sharpening of the diamond wheel has microscopic notches of different degrees (ie, micro chipping and sawing). Graphite high-speed cutting tool performance and stability put forward higher requirements, especially diamond coating tools must be passivated by the knife edge before coating to ensure the firmness and service life of the coating. The purpose of tool passivation is to solve the defect of the micro-notch of the cutting edge of the above-mentioned sharpened blade, so that the front value is reduced or eliminated, and the smoothness and rigidity are achieved.
5, the machining conditions of the tool
Choosing the right machining conditions has a considerable impact on the life of the tool.
(1) Cutting method (shun milling and up milling), the cutting vibration during down milling is smaller than the cutting vibration of up milling. The cutting thickness of the tool during down-cutting is reduced from the maximum to zero. After the tool is cut into the workpiece, there is no knives caused by cutting the chip. The rigidity of the process system is good and the cutting vibration is small. When cutting the thickness of the tool during the reverse milling From zero to maximum, the cutting edge will be scratched on the surface of the workpiece due to the thin cutting thickness. At this time, if the cutting edge encounters hard spots in the graphite material or chip particles remaining on the surface of the workpiece, it will cause the tool. The knives or flutter, so the cutting vibration of the up-cut milling is large;
(2) Blowing (or vacuuming) and impregnating EDM liquid processing, timely cleaning the graphite dust on the surface of the workpiece, which is beneficial to reduce the secondary wear of the tool, prolong the service life of the tool, and reduce the graphite dust on the screw and guide rail of the machine tool. influences;
(3) Select the appropriate high speed and the corresponding large feed.
In summary of the above points, the material of the tool, the geometric angle, the coating, the reinforcement of the cutting edge and the machining conditions play different roles in the service life of the tool, which are indispensable and complementary. A good graphite tool should have a smooth graphite powder chip flute, long service life, deep engraving processing, and can save processing costs.
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