Common quality defects in extrusion process of insulated cables and their treatment

Plastic Scorch is a common quality defect in the plastic extrusion process of insulated cables, which is mainly manifested as follows: the temperature display is ultra-high; There is a lot of smoke and strong irritating smell at the die mouth of the machine head, and there is a popping sound in serious cases; The extruded plastic layer has coke particles, etc; There are continuous bubbles at the glue joint; The main causes are:

1) The temperature is controlled to reach the thermal degradation temperature of plastics;

2) The screw has not been cleaned for a long time, and the accumulated burnt material is extruded with the molten plastic;

3) The heating or shutdown time is too long, which causes the plastic in the barrel to decompose due to long-term heating;

4) The temperature control instrument is out of control or inaccurate, resulting in high-temperature decomposition;

5) The cooling system of the extruder was not opened, resulting in overheating of material shearing friction. Therefore, during the extrusion of insulated cables, it is necessary to strengthen the inspection of whether the heating and cooling systems work normally; The extrusion temperature shall be set according to the process requirements and the screw speed; Reasonably control the heating time and regularly clean the extrusion system.

2. Poor plasticization of extrudates has been mentioned in the temperature control requirements mentioned above. Generally, poor plasticization is mainly manifested as follows: the extruded cladding has toad skin; The plastic surface is dark, Matt and has small cracks; The extruded coating has obvious seam at the glue joint; The main causes are:

1) The temperature control is too low, especially at the nose;

2) Other plastic particles with different properties are mixed in the insulating or sheathing materials;

3) The screw turns the plastic too fast, and the plastic is not fully plasticized;

4) The plastic itself has quality problems. For the above reasons, attention should be paid to the rationality of extrusion temperature control for insulated cables; The qualified product name of the received materials shall be confirmed; It is not allowed to blindly pursue the output and improve the extrusion speed; Strengthen the storage of raw materials, especially in the plastic drying process; Reasonable die matching to enhance extrusion pressure and screw reflux. power cable price

3. There are air holes or bubbles on the cross section of the extruded layer, which are mainly caused by:

1) Excessive temperature control (especially in the feed section);

2) Moisture in plastic;

3) After parking for a long time, the decomposed plastic is not completely removed;

4) High humidity in natural environment;

5) There is water in the cable core or the content of vaporization is too high.

For the above reasons, the temperature of each section of the screw should be reasonably controlled; Pre dry the materials used in advance; Strict process operation requirements to improve the ability to judge the plasticization degree of plastics; Pay attention to the production environment and storage conditions of materials. Among them, the extrusion size is unqualified, which is mainly manifested as eccentric core; Sheath thickness or outer diameter out of tolerance; The appearance of extruded coating is not qualified, which mainly shows that there is scratch on the surface of extruded coating; Rough with trachoma or microcrack; Any defect caused by insufficient plasticization.