Quality defects and treatment methods in the extrusion process

1. Plastic scorch plastic scorching is a common quality defect in the plastic extrusion process. Its attention is expressed as: the temperature display is super high; the head die mouth has a lot of smoke, a strong irritating sensation, and when there is severe crackle; There are coke particles in the layer; there are continuous bubbles in the glue seam; the main causes of the note are:

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

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

3) Heating or down time 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, resulting in pyrolysis;

5) Extruder cooling system does not open, resulting in overheating of the shear friction of the material.

Therefore, in the extrusion process should be strengthened to check the heating, cooling system is working properly; extrusion temperature settings should be based on process requirements and the screw speed; reasonable control of temperature and time, regular cleaning of the extrusion system.

2. Bad plasticizing of extrudates In the above mentioned temperature control requirements, plasticizing problems have been mentioned. Generally, poor plasticizing is mainly manifested in the following: Extrusion coating is tanned; plastic surface is black, dull, and Small cracks; Extrusion layers have obvious seams at the glue; the main causes are:

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

2) Insulation or sheath material mixed with other plastic particles of different properties;

3) Screws are too fast to turn plastic and plastics are not fully plasticized;

4) The plastic itself has quality problems.

For the above reasons, we should pay attention to the rationality of the extrusion temperature control; confirm the quality of the used materials; we must not blindly pursue the output and increase the extrusion speed; strengthen the storage of raw materials, especially in the plastic drying process; To enhance the extrusion pressure and screw reflux.

3. There are pores or bubbles in the extruded clad section. The main causes are:

1) The temperature is too high (especially the feed section);

2) The plastic damps moisture;

3) Long-term parking, decomposition of plastics has not been eliminated;

4) High humidity in the natural environment;

5) There is excessive water or vapor in the core.

For these reasons, it is necessary to reasonably control the temperature of each section of the screw; to pre-dry the materials used in advance; strict process operation requirements, improve the ability to judge plastic plasticity; pay attention to the production environment and material storage conditions.

4. Extrusion size is unqualified, mainly manifested as eccentric core; sheath thickness or outer diameter is poor; its main causes are:

Extrusion and traction speeds are not stable;

1) The core diameter changes too much;

2) Extrusion temperature is too high to reduce the amount of extrusion;

3) too much impurities in the plastic block in the filter to reduce the plastic flow;

4) The tension of the retractable line is not stable;

5) The core selection is too large (squeeze type) or the length of the core lead line area is too short and eccentric;

6) Improper choice of die spacing;

7) The temperature of the extrusion head is not uniform;

8) The concentricity of the extrusion die is not adjusted;

9) The feed inlet temperature is too high to make feed difficult to affect the material flow;

For these reasons, it is necessary to regularly measure the outer diameter of the jacket in time to adjust; reasonable selection and adjustment of the extrusion die; pay attention to the tension changes in the retractable line timely adjustment; temperature control should be consistent with the requirements;

5, The failure rate of the longitudinal band adhesive strength is mainly due to:

1) The extrudate temperature is too low;

2) Overfilling grease paste;

3) The production line speed is too fast, so that the jacket is rapidly cooled;

4) The temperature of the hot water tank is too low and it is close to the die;

5) The mold-drawing ratio is too small, or the mold is unreasonable, making it loose;

6) The melting point of the vertical wrapping composite membrane is too high;

According to the above reasons, should pay attention to the requirements of the mold, if necessary, according to the adjustment of the core; can not let the jacket is rapidly cooled in order to improve the bonding ability; can not be increased to reduce the head temperature of the jacket setting; pay attention to the filling of the ointment In order to scratch the thin layer by touching the cable core with your finger, it is better.

6. The unsatisfactory appearance of the extruded package, the appearance of the unsatisfactory appearance of the extruded package is mainly due to the abrasion of the surface of the extruded clad; the rough has trachoma or micro-crack; and any defect caused by plasticization is not enough. The main reason is:

1) The selection of extrusion die sets is irrational. Too small causes hemp pattern; excessively large causes disjoint or loose extrusion;

2) Impurities stuck in the extrusion die sleeve to scratch the sheath surface.

3) Extrusion head heating temperature is too high to cause rough, or temperature is too low to cause micro-cracking;

4) damage to the sizing zone;

5) The sheath is scratched in the sink;

For the above reasons, defects can be eliminated or prevented in production.

In actual production, in addition to the above-mentioned defects and causes, there are issues such as the problem of the line layout, the problem of the overlapping width of the vertical package, and the shape of the bamboo section. We will observe and summarize more in production, grasp the main and the essence of the problem, and we will be able to solve it, and do a better job in the quality level of the cable.