In the cutting process, tool wear is mainly caused by mechanical action and thermochemistry. The specific reasons are as follows: (1) Abrasive wear. During the cutting process, the hard spots in the workpiece material or the debris of the built-up chips adhered to the workpiece and the chips will cause groove marks on the surface of the tool to wear the tool.
A milling machine tool material
CNC milling tool materials are the fundamental factors that determine the cutting performance of the tool, and have a great influence on machining efficiency, machining quality, machining cost, and tool life. The harder the milling tool material, the better the wear resistance, the higher the hardness, the lower the impact toughness and the more brittle the material. Hardness and toughness are a contradiction, and it is also a key to overcome the tool material. For graphite tools, the ordinary TiAlN coating can be selected on the appropriate selection of a relatively good toughness, that is, a little higher cobalt content; for diamond-coated graphite tool, the hardness of the material can be appropriately selected a little better That is, the cobalt content is slightly lower;
Second, the milling cutter geometry angle
The selection of the geometrical angle of the graphite milling tool helps to reduce the tool magazine vibration, and in turn, the graphite workpiece does not collapse easily.
1. In the front corner, when the negative rake angle is used to process graphite, the cutting edge of the milling cutter has good strength and good resistance to impact and friction. With the decrease of the absolute value of negative rake angle, the flank wear area does not change much, but The overall trend is decreasing. With the positive rake angle machining, the cutting edge strength is weakened with the increase of the rake angle, which in turn leads to an increase in flank wear. When the negative rake angle is processed, the cutting resistance is large and the cutting vibration is increased. When the rake angle is used for machining, the tool wear is severe and the cutting vibration is also large.
2. In the rear corner, if the relief angle increases, the tool edge strength decreases, and the flank wear area gradually increases. After the tool clearance angle is too large, the cutting vibration increases.
3. When the helix angle is small, when the helix angle is small, the longest blade length of the same workpiece cutting into the graphite workpiece at the same time is the longest, the maximum cutting resistance, and the maximum cutting impact force of the cutter, so the tool wear, milling force and cutting vibration are the largest. When the helix angle is larger, the direction of the resultant force of milling is deviated from the surface of the workpiece, and the cutting impact caused by the disintegration of the graphite material is intensified. Therefore, the tool wear, the milling force and the milling vibration of the milling machine also increase. Therefore, the influence of tool angle change on the tool wear, milling force and cutting vibration is caused by the combination of rake angle, relief angle and helix angle. Therefore, attention must be paid to the selection.
Through a large number of scientific tests on the processing characteristics of graphite materials, PARA cutters optimize the geometric angle of the relevant tools, thereby greatly improving the overall cutting performance of the tool.
Third, the tool coating
Diamond-coated tools have the advantages of high hardness, good wear resistance, low friction coefficient, etc. At this stage, diamond coating is the best choice for graphite processing tools, and it can best reflect the superior performance of graphite tools; the hardness 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, domestic diamond coating technology is still in its infancy and there is a large investment in costs, so diamond coatings are in the near future. There will not be much development, but we can optimize the tool angle, material selection, etc., and improve the structure of the common coating on the basis of ordinary tools, to a certain extent, it can be applied in the processing of graphite.
Fourth, milling machine tool edge strengthening
The passivation technology of cutting edges of CNC milling cutters is an issue that has not been widely considered and is an important issue. There are microscopic gaps (ie, micro-disintegration and sawing) with different degrees of extent in the edge of the hard alloy tool after diamond grinding. High-speed cutting tool performance and stability of graphite put forward higher requirements, in particular, diamond-coated tools in the coating before the knife must pass through the passivation treatment in order to ensure the coating's solidity and service life. The purpose of the passivation of the tool is to solve the above-mentioned defect of the micro-gap of the tool edge after the sharpening, so that the frontal value is reduced or eliminated to achieve smooth and smooth, which is both sharp, strong and durable.
Fifth, the tool machining conditions
Choosing the right processing conditions has a considerable effect on the life of the tool.
1. Cutting methods (climbing and up-cut). The cutting vibration during down milling is less than that of up-cut milling. The cutting thickness of the tool during crush milling is reduced from the maximum to zero. After the tool cuts into the workpiece, the knife phenomenon caused by cutting no chips will not occur. The rigidity of the process system is good, and the cutting vibration is small; when the milling is performed, the cutting thickness of the tool is reduced. From zero to maximum, the tool will scratch a certain path on the surface of the workpiece due to the thin cutting thickness. At this time, the edge will cause the tool if it encounters a hard point in the graphite material or chip particles remaining on the workpiece surface. Missile or flutter, so the cutting vibration of the counter mill is large;
2. Insufflation (or vacuuming) and impregnation of electrospark fluids to remove the graphite dust on the surface of the workpiece in a timely manner will help reduce the secondary wear of the milling machine tool, prolong the service life of the tool, and reduce the graphite dust on the screw and guide of the machine tool. influences;
3, select the appropriate high speed and the corresponding large feed.
To summarize the above points, the materials, geometrical angles, coatings, cutting edge strengthening, and machining conditions of the CNC machining of the milling machine tool play different roles in the service life of the tool. They are indispensable and complementary. A good graphite tool should have a smooth graphite powder flutes, a long service life, be able to deepen the engraving process, and save processing costs.