The tool is hard, but with the delay of service time, the tool will also have certain wear. What are the several reasons that affect the wear of the tool? Through summarizing, several reasons are obtained.
I. Tool Materials
Numerical control tool material is the fundamental factor that determines the cutting performance of the tool and 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 its hardness, the lower its impact toughness, and the more brittle the material. Hardness and toughness are a pair of contradictions, and also a key to be overcome by cutting tool materials. For graphite tools, ordinary TiAlN coatings can be appropriately selected with relatively better toughness in material selection, i.e. with slightly higher cobalt content. For diamond coated graphite cutting tools, the one with relatively better hardness, i.e. the one with slightly lower cobalt content, can be appropriately selected in material selection.
Second, the geometric angle of the tool
Choosing a suitable geometric angle for the graphite tool is helpful to reduce the vibration of the tool. In turn, graphite workpieces are not easy to collapse.
1. rake angle. when graphite is processed with negative rake angle, the cutting edge strength of the cutter is better, and the performance of resisting impact and friction is better. with the decrease of the absolute value of negative rake angle, the wear area of the flank surface changes little, but the overall trend is decreasing. when graphite is processed with positive rake angle, the cutting edge strength of the cutter is weakened with the increase of the rake angle, which leads to the aggravation of the wear of the flank surface. When machining with negative rake angle, the cutting resistance is large, which increases the cutting vibration. When machining with large positive rake angle, the tool wear is serious, and the cutting vibration is also large.
2. Rear angle. If the rear angle increases, the cutting edge strength of the cutter decreases and the wear area of the rear face gradually increases. When the back angle of the cutter is too large, the cutting vibration will be strengthened.
3. When the helix angle is small, the length of the cutting edge that cuts into the graphite workpiece at the same time on the same cutting edge is the longest, the cutting resistance is the largest, and the cutting impact force borne by the cutter is the largest, so the cutter wear, milling force and cutting vibration are the largest. When the helix angle is large, the direction of milling resultant force deviates from the surface of the workpiece to a large extent, and the cutting impact caused by graphite material breakage is intensified, thus the tool wear, milling force and cutting vibration are also increased. Therefore, the influence of tool angle change on tool wear, milling force and cutting vibration is produced by the combination of front angle, rear angle and spiral angle, so more attention must be paid to the selection.
Through a large number of scientific tests on the processing characteristics of graphite materials, PARA tool optimizes the geometric angles of relevant tools, thus greatly improving the overall cutting performance of the tool.
III. Coating of Cutting Tools
Diamond coated cutting tools have the advantages of high hardness, good wear resistance, low friction coefficient and the like. At present, diamond coating is the best choice for graphite processing tools and can best reflect the excellent service performance of graphite cutting tools. The advantages of diamond coated cemented carbide tools are that they combine the hardness of natural diamond with the strength and fracture toughness of cemented carbide. However, the diamond coating technology in China is still in the initial stage, and the investment in cost is very large, so the diamond coating will not have much development in the near future. However, we can optimize the angle, material selection and other aspects of the cutter and improve the structure of the common coating on the basis of the common cutter, which can be applied to graphite processing to some extent.
Diamond coated tool
There are essential differences between the geometric angles of diamond coated tools and common coated tools, so when designing diamond coated tools, due to the particularity of graphite processing, the geometric angles can be appropriately enlarged, the cutting groove can be enlarged, and the wear resistance of the cutting tool front will not be reduced. For ordinary TiAlN coating, although its wear resistance is significantly improved compared with uncoated tools, its geometric angle should be appropriately reduced when processing graphite to increase its wear resistance compared with diamond coating.
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, mature and economical coating companies abroad are only limited to Europe. PARA, as an excellent graphite processing tool, also uses the world's most advanced coating technology to process the surface of the tool to ensure the processing life and the economical and practical use of the tool.
Four, the strengthening of the cutting edge of the tool
Cutting edge passivation technology is a very important problem that has not been widely paid attention to. The cutting edge of cemented carbide tool sharpened by diamond grinding wheel has micro-notches (i.e. micro-chipping and sawing) with different degrees. The performance and stability of graphite high-speed cutting tools require higher requirements, especially the diamond coated tools must be passivated before coating to ensure the firmness and service life of the coating. The purpose of tool passivation is to solve the defects of the micro-gap of the sharpened cutting edge of the tool, to reduce or eliminate the front value, and to achieve the purpose of smoothness, smoothness, sharpness, firmness and durability.
Five, cutting tool machining conditions
Choosing appropriate processing conditions has a considerable impact on the life of the tool.
1. Cutting mode (forward milling and reverse milling). Cutting vibration during forward milling is smaller than that of reverse milling. When milling, the cutting thickness of the cutting tool is reduced from the maximum to zero. After cutting the workpiece, the tool will not bounce due to cutting chips. The rigidity of the process system is good and the cutting vibration is small. During reverse milling, the cutting thickness of the cutter increases from zero to the maximum. At the initial cutting stage of the cutter, 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 graphite material or chip particles remaining on the surface of the workpiece, it will cause the cutter to bounce or chatter, so the cutting vibration of reverse milling is large.
2. Blowing (or dust suction) and dipping in electric spark liquid for processing, and cleaning graphite dust on the surface of the workpiece in time, are conducive to reducing secondary wear of the cutter, prolonging the service life of the cutter, and reducing the influence of graphite dust on the lead screw and guide rail of the machine tool;
3, choose the appropriate high speed and the corresponding large feed.
Summarizing the above points, the material, geometric angle, coating, strengthening of cutting edge and machining conditions of the cutter play different roles in the service life of the cutter, which are indispensable and complement each other. A good graphite cutter should have smooth graphite dust removal grooves, long service life, deep engraving and processing, and can save processing cost.
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No matter how hard the tool is, it will wear out. Do you know why it wears out?
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