When the tool is cutting metal, especially when cutting steel continuously, the chips cannot be rolled up as they are. This is not because the chips are too hard, but because the length of the chips changes. At the same time, the chips will become wider and thicker. In other words, the shape of the chips under different cutting elements is also very different. The thickness of the chip is generally several times the original, and the length is several times the original. Therefore, the chips obtained by cutting at a certain cutting speed are equivalent to being produced at a fraction of the cutting speed. However, this ratio will vary greatly depending on the rake angle of the tool.
As shown in the figure, the size of the rake angle will affect the shape and size of the chip. If the rake angle is 0°, the shear angle is small, the chip deformation is large, and it is thick and short. Because of the large deformation, the size of the rake angle is related to the size of the total cutting force. Conversely, if the rake angle becomes larger, the shear angle will naturally become larger.
Four types of chips
Due to the difference in the rake angle of the tool, cutting speed, workpiece material, tool engagement, and feed rate, the resulting cutting will vary. Generally, it is divided into four types as shown in the figure. The processing conditions in the figure are: the rake angle of the tool is 0°, the tool engagement is 2mm, and the cutting speed and workpiece material are different.
Chips fly out continuously from the front of the tool, which is beneficial to the cutting conditions, the machined surface and the tool.
2. Crush type
Use the shear angle to cut, and the chips are separated from the workpiece.
When cutting materials with high plasticity, the chips formed by cutting off individual units in the chips have poor surface quality.
4. Fragmentation type
Chips break and flake off the surface. A fracture occurred on the workpiece, and the chips were considered to be peeled from the fracture.