The extruder screw is an important component that plasticizes plastic or rubber and other materials under high temperature and high pressure. The break of the screw will seriously affect the normal operation and product quality of the extruder, so it is necessary to understand the reasons and preventive measures to understand the reasons and preventive measures. According to different breaks and positions, the cause of the screw break can be divided into the following categories:

First, torsional fatigue break: This fracture usually occurs at the root of the screw, because the screw is caused by the torque that exceeds its torque during operation. The characteristics of twisting fatigue are round, with radial cracks on the surface, and the split distance has significantly reduced. The main reasons for reversing fatigue breaks are the following points:

▪️ The design of the screw is unreasonable, resulting in insufficient strength or stress concentration of the screw.

▪ ️ The quality of the screw is poor, resulting in rough surfaces of the screw, unevenness or defects of the hardening layer.

▪️ The use of screws is poor, causing the screw to be affected by impact loads, temperature changes, or hard impurities in materials.

▪ ️ Improper maintenance of the screw causes the problem of insufficient lubrication of the screw, the inaccurate or not firmly installed.

Second, bending fatigue break: This break usually occurs in the middle of the screw, which is caused by repeated bending stress during the screw during operation. The characteristic of bending fatigue is elliptical, with rivers or shell -like cracks on the surface, and there is no obvious twist. The main reasons for bending fatigue breaks are the following points:

▪️ The coordination between the screw and the barrel is too large, causing the material to have a side thrust on the screw.

▪️ The conflict between the screw and the machine tube causes the screw to have eccentricity during the operation of the screw.

▪️ The connection between the screw and the driver is not firm, resulting in a swinging power during operation.

▪️ The screw itself has bending deformation or internal stress, causing the screw to generate additional stress during operation.

Third, heat fatigue break: This fracture usually occurs at the contact between the screw and the tube, which is caused by repeated temperature changes during the screw during operation. The characteristics of the heat fatigue are the mesh or fish scale, and there are multiple holes or cracks on the surface, and there is no obvious plastic deformation. The main causes of heat fatigue break are the following points:

▪️ The temperature difference between the screw and the barrel is too large, resulting in thermal strain during the operation of the screw.

▪️ The thermal expansion coefficient between the screw and the tube does not match, causing the screw to generate thermal stress during operation.

▪️ The surface treatment of the screw is poor, resulting in insufficient heat resistance or corrosion resistance of the screw.

▪️ The working temperature of the screw is too high or too low, causing the strength or toughness of the screw to be reduced.