Plastic burning is a common quality defect in the plastic extrusion process, mainly manifested as: excessively high temperature display; There is a large amount of smoke and strong irritant odor at the die mouth of the machine head, and in severe cases, there may be a popping sound; The extruded plastic layer contains particles such as coke.

Common quality defects and treatment methods of cable products in extrusion molding process

1. Plastic burning: Plastic burning is a common quality defect in the plastic extrusion process, mainly manifested as: excessively high temperature display; There is a large amount of smoke and strong irritant odor at the die mouth of the machine head, and in severe cases, there may be a popping sound; There are burnt particles in the extruded plastic layer; There are continuous bubbles at the adhesive joint; The main reasons for this are:

(1) Ultra high temperature control to reach the plastic thermal degradation temperature;

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

(3) Excessive heating or shutdown time can cause the plastic inside the barrel to decompose due to prolonged heating;

(4) The temperature control instrument loses control or is inaccurate, causing high-temperature decomposition;

(5) The cooling system of the extruder is not turned on, causing material shear friction overheating. Therefore, during the extrusion process, it is necessary to strengthen the inspection of whether the heating and cooling systems are working properly; The setting of extrusion temperature should be determined according to the process requirements and the speed of the screw; Reasonably control the heating time and regularly clean the extrusion system for cable products.

2. The problem of poor plasticization of extruded materials was mentioned in the temperature control requirements earlier. Generally, poor plasticization is mainly manifested as: the extruded layer has a skin like appearance; The surface of the plastic is blackened, dull, and has small cracks; The extruded layer has obvious seams at the adhesive joint; The main reasons for this are:

(1) The temperature control is too low, especially in the nose area;

(2) Mixing other plastic particles of poor quality in the insulation or sheath material;

(3) The screw rotates too quickly, causing the plastic to fail to plasticize;

(4) Plastic itself has quality issues. For the above reasons, attention should be paid to the rationality of extrusion temperature control for cable products; The quality and product name of the materials used should be confirmed; We cannot blindly pursue output and increase extrusion speed; Strengthen the storage of raw materials, especially in the plastic drying process; Reasonably allocate molds to enhance extrusion pressure and screw reflux.

3. The cross-section of the extruded layer has pores or bubbles, which are mainly caused by:

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

(2) Plastic is damp and has moisture;

(3) Long term parking, incomplete removal of decomposed plastic;

(4) High humidity in the natural environment;

(5) There is too much water or gas content in the cable core.

For the above reasons, the temperature of each section of the screw should be reasonably controlled; Pre dry the materials used for cable products in advance; Strict process operation requirements to improve the ability to evaluate the degree of plastic plasticization; Pay attention to the production environment and material storage conditions. The extrusion size is unqualified, mainly manifested as core deviation; The thickness or outer diameter of the sheath exceeds the tolerance; The unqualified appearance of the extruded package is mainly manifested by scratches on the surface of the extruded layer; Coarse with sand holes or microcracks; Any defects caused by insufficient plasticization.