Wear patterns
2. Wear patterns can be classified as follows:
1) loss of rake face
When cutting plastic materials at high speed, the part near the cutting force on the rake face will be worn into the crescent concave shape under the action of chips, so it is also called crescent depression wear. At the early stage of wear, the tool rake angle increases, which improves the cutting conditions and facilitates chip curling and breaking, but when the crescent depression increases further, the strength of the cutting edge is greatly weakened, which may eventually lead to the collapse and breakage of the cutting edge. In cutting brittle materials, or with lower cutting speed and thinner cutting thickness of plastic materials, generally will not produce crescent depression wear.
2) knife point wear
The wear of the tool tip is the wear on the back face of the tool tip arc and the adjacent flank face, which is the continuation of the wear on the back face of the tool. Because of the poor heat dissipation condition and the stress concentration, the wear rate is faster than the flank, and sometimes a series of grooves with the distance equal to the feed amount are formed on the flank, which is called furrow wear. They are mainly due to the hardened layer of the machined surface and the resulting cutting lines. It is easy to cause furrow wear in hard-to-cut materials with high hardening tendency in cutting. The tool tip wear has the greatest influence on the workpiece Surface roughness and machining accuracy.
3) flank wear
When cutting plastic materials with a large thickness, the back face of the tool may not be in contact with the workpiece due to the presence of chip accretion. In addition, the flank usually comes into contact with the workpiece and forms a wear band with a back angle of 0 on the flank. Generally, in the middle of the working length of the cutting edge, the wear of the flank is more uniform, so the wear degree of the flank can be measured by the width of the wear band of the flank of the cutting edge in VB.
Because all kinds of cutting tools in different cutting conditions almost will have the flank wear, especially when cutting brittle materials or cutting plastic materials with a smaller thickness, the tool wear is mainly the flank wear, and the width of the wear belt VB measurement is relatively simple, so it is usually used to express the degree of tool wear VB. The bigger VB is, not only will the cutting force increase, cause cutting vibration, but also will affect the tool point arc wear, thus affecting the machining accuracy and surface quality.
