Defects and treatment methods in extrusion processing:
1, plastic scorch
Plastic scorch is a common quality defect in plastic extrusion process. Its attention is as follows: the temperature is super high; the die has a large amount of smoke, strong irritating odor, and there is a bursting sound when it is severe; the extruded plastic layer has coke particles; There are continuous bubbles at the joints; the main reasons for the injection are:
1) The temperature control is too high to reach the thermal degradation temperature of the plastic;
2) The screw has not been cleaned for a long time, and the accumulated scorch is extruded with the molten plastic;
3) Heating or downtime is too long, so that the plastic in the barrel is decomposed by heat for a long time;
4) The temperature control instrument is out of control or misaligned, causing pyrolysis;
5) The extruder cooling system is not opened, causing the material to shear friction and overheat.
Therefore, during the extrusion process, it should be checked whether the heating and cooling system work normally; the setting of the extrusion temperature should be determined according to the process requirements and the rotation speed of the screw; the temperature is controlled reasonably, and the extrusion system is cleaned regularly.
2, poor plasticization of the extrudate
In the above, the plasticization problem has been mentioned in the temperature control requirements. The general plasticization failure is mainly as follows: the extrusion layer has a suede-like sample; the plastic surface is black, dull, and has small cracks; the extrusion layer is combined There are obvious seams at the glue; the main reasons for this are:
1) The temperature control is too low, especially the nose part;
2) Other plastic particles of different properties are mixed in the insulating or sheathing material;
3) The screw is too fast to plastic, and the plastic is not completely plasticized;
4) There are quality problems in the plastic itself.
For the above reasons, attention should be paid to the rationality of extrusion temperature control; the quality of the materials to be used should be confirmed; the extrusion speed should not be pursued blindly; the storage of raw materials should be strengthened, especially in the plastic drying process; To enhance extrusion pressure and screw backflow.
3. There are pores or bubbles in the section of the extrusion layer, which are mainly caused by:
1) The temperature control is too high (especially the feed section);
2) The plastic is damp and has moisture;
3) Parking for a long time, the plastic is not excluded;
4) The natural environment has high humidity;
5) The water or vapor content in the core is too high.
For the above reasons, the temperature of each section of the screw should be reasonably controlled; the materials used should be pre-dried in advance; the requirements of strict process operation should be improved, and the ability to judge the plasticization degree of plastics should be improved; attention should be paid to the production environment and storage conditions of materials.
In actual production, in addition to the above-mentioned defects and causes, there are problems such as the wiring problem, the vertical overlap width problem, and the shape of the bamboo joint. We will observe and summarize more in the extrusion processing, and grasp the main and essence of the problem, we will solve it and make the cable quality level better.