Qingdao Trusty Plastic Machinery Co.,Ltd.

The cause of the phenomenon of screw "holding dead"

Release time:2022-09-30 09:33

A plastic extruder is a kind of mechanical equipment that can produce plastic products by efficient and continuous extrusion. Its core part is the screw. The phenomenon of "locking" the screw is a very serious equipment failure. If in the actual production process, it will not only interrupt the production process, affect the quality and output of products, but also cause irreversible equipment damage to the extruder equipment.

As an enterprise with many years of experience in the production of extruders and a full set of equipment for extruder production lines, Qingdao Trusty Plastic Machinery Co., Ltd. suggests that the screw should be shut down immediately in case of a "locking" phenomenon. First of all, it should be noted that if the extruder has protective devices such as screw stall and current increase, it will generally not cause excessive equipment damage. However, if the protective device of the extruder equipment fails, the locking failure of the extruder screw is not necessarily caused by the direct stop of the screw rotation. In most cases, the screw can still rotate, but the speed slows down, which will cause greater damage to the equipment. Now the staff needs to make timely judgments, for example, when there is a harsh metal scratch or the current of the main extruder increases sharply, they should stop the machine immediately.

In case of failure, we must first determine the cause of the failure. Generally, we can analyze and deal with it from the following points:

1. For the old extruder equipment, we can give priority to the serious deformation of the screw or barrel;

2. If there are too many foreign matters in the plastic raw materials used by the extruder, especially if the foreign matters are metal foreign matters, it is very easy to cause the screw to jam, and at the same time, it will cause irreversible damage to the screw and barrel;

3. The extruder fails to make pre-production preparations when it is started up, such as the barrel temperature is too low, the residual materials in the barrel are not completely melted, or the screen changer is blocked. In this case, the sudden start-up and production may cause the melt pressure in the barrel to be too high, which may cause the screw to deform and finally cause the screw to jam;

4. The design of the screw and the barrel is unreasonable, for example, the compression ratio of the screw design is too large or the thermal expansion coefficient of the material used for the screw and the barrel is too different. In these two cases, when the selection of screw and barrel materials is unreasonable, sometimes we can solve the problem by modifying the screw and cooling the core.

In fact, the phenomenon of screw "locking" in extruder equipment is relatively rare. As long as it can be stopped in time when a fault occurs, it will generally not cause excessive losses.