Analysis of the causes of irregular cutting of underwater pelletizers-pelletizing knife holder and pelletizing knife（1）
Problem analysis
According to the phenomenon of cutting out irregular particles, and then based on past maintenance experience, we decided to start the analysis from the following aspects.
(1) Moving knife
①The front corner. During the cutting process, the force distribution of the movable knife edge is shown in Figure 1.
Image 1(The-force-of-the-cutting-motor-knife-in-the-cutting-process)
The cutting force on the tip of the tool in Figure 1 is the resultant force of the reaction force p of the casting strip on the cutting edge and the friction force f on the back of the knife.
The rake angle γ, the relief angle α and p, f form a quadrilateral, and the law of cosines can be used Get the cutting force F: F²=f²+p²+2fpcos(γ+α)
According to the formula, as the γ angle increases, the total cutting force F will fall within a certain range, showing a cosine relationship drop, and can reduce the plastic deformation of the pellets and improve the appearance quality.
For synthetic resin materials, the strength and hardness are not high, but the plasticity is relatively large, so a larger rake angle should be selected.
But the premise of increasing the rake angle is to ensure that the knife has sufficient strength.
②Back corner. The function of the movable knife clearance angle is to reduce friction. The casting strip continued to drop at the moment of cutting.
There is friction between the cast strip and the back of the blade, and the friction makes the cast strip move irregularly during the conveying process, causing random cutting.
It can be seen that the relief angle is also to choose a larger angle under the premise of ensuring the strength of the knife.
Quote-[1] Sun Lin. Analysis of the causes of irregular cutting of underwater pelletizers and solutions [J]. Silicon Valley, 2014,000(013): 107-107,104
