A. 

The clearance between screw and barrel is not proper. The screw may have been installed out of line and rubbed against the barrel. We advise you to check the installation of the screw barrel.
In the case of old extruder, because of the out of shape extruder body frame, the large side of the screw will rub against the shaft. The right thing to do is to adjust the extruder body frame. But this is always difficult for most end users. Therefore, we advise a simple way to solve this problem. You need to take out the screw and check the friction part in which you will find it to be burned and the color is dark. Then use a polisher to polish this part off.

Q

How to maintenance the screw and barrel?

A. 

Check regularly and plan in advance. As part of extruder maintenance, determining the wear degree of the screw barrel is very important. According to different wearing degrees, you will meet troubles during the extrusion process. The material will gush out from the vent holes and decrease the output. Thus, checking the clearance of the screw barrel regularly is a good habit. You will know to what extend the nitride level of the barrel’s interface has been worn and can calculate the speed of wearing. Then you can make a plan of replacement in advance. Especially in the case of your extruder model is unique and the manufacturers don’t have the screw barrel in stock.

Q

What’s the reason of breakdown of screw and barrel?

A. 

1. In the process of extrusion, the surface of screw and barrel will be worn. This will make the clearance between screw and barrel bigger and the back-flow of material makes residence time in the barrel of material longer. Materials such as PE will decomposed corrosive gas which leads to screw barrel more worn.
2. In addition, formulation fillers such as calcium and glass fiber will make screw barrel worn out quickly.
3. Abnormal reasons such as hard things like snag is fed into screw and makes rotating torque exceed screw normal load.