Causes of screw and barrel damage in extruder

The combined working quality of the screw and barrel in twin-screw extrusion machinery has a significant impact on material plasticization, product quality, and production efficiency. The manufacturing precision and assembly clearance of these two components determine their working quality. When the two parts are severely worn and the productivity of the extrusion machinery decreases, maintenance or replacement of the screw and barrel should be arranged.

1. As the screw rotates inside the barrel, friction between the material and the barrel gradually wears down the working surfaces of both the screw and the barrel: the screw diameter gradually decreases, while the inner diameter of the barrel gradually increases. Consequently, the diametrical clearance between the screw and the barrel gradually enlarges as both components wear. However, since the resistance from the head and the breaker plate at the front of the barrel remains unchanged, this increases the leakage flow of the extruded material as it moves forward—meaning more material flows from the diametrical clearance toward the feed direction. As a result, the output of the extruder decreases. This phenomenon prolongs the material's residence time in the barrel, leading to material degradation, and the decomposition of some materials can cause corrosion to both the barrel and the screw.

2. If the material contains elements such as calcium carbonate, it can accelerate the wear of the screw and barrel.

3. Due to uneven plasticization of the material or the presence of metal impurities mixed into the material, the torque of the screw suddenly increases, exceeding the strength limit of the screw, causing the screw to break. This is an unconventional accidental damage.

4. When installing the screw and barrel, if the levelness, straightness, and clearance are not properly adjusted, and the fastening screws are not tightened, friction between the screw and barrel occurs when the twin-screw extrusion machinery starts, accelerating damage to the barrel.

Before starting the puffing machinery, if the preheating time is insufficient, the raw materials accumulated in the screw barrel are not fully softened, the startup torque is too high, or there are unsoftened large material blocks, it may cause the screw barrel to be twisted or broken, and may also lead to damage to the gearbox.

High-quality internal puffing machines generally add overload protection to the main motor of the puffing machine, which can protect the screw barrel to a certain extent and greatly reduce the occurrence of screw twisting. However, if the stress point is at a weak part of the screw or occurs suddenly, the screw may still be damaged.

Jinan Datong Machinery Equipment Co., Ltd. can configure the screws and barrels required for your puffing machine production. Welcome to inquire and order.