一、 The reason for the mold

1. There is anti-rust oil and lubricating oil on the mold.

2. If the gates of the mold are too small or too rough, a large amount of friction heat will be generated, and if the mold is not well vented, it will cause the gas to burn and produce obvious black streaks (black spots).

二、The reason for the equipment

1. The dryer motor has been running for a long time, and it must be cleaned regularly;

2. The dryer filter must be cleaned and replaced regularly, otherwise it will enter foreign matter or discolor and agglomerate the material due to poor ventilation;

3. The dryer is not (completely) sealed due to the negligence of the operator or the lack of operating equipment, resulting in the entry of dust in the air; or dust scattering, contaminating the surrounding products and materials in the crusher; Or the barrel is too large, the operation is not easy, ignoring the angle (the pipe and its interface) and other factors, resulting in the process of changing the barrel, the barrel is not completely clean.

4. Long-term production and operation, usually not taking good protection, resulting in scattered dust mixed with the equipment;

5. The shielding of the pulverizer is not in place, resulting in contamination and contamination of other materials;

6. The crusher should be used as black and white as possible;

7. If the nozzle aperture is too small or the inner surface is rough, a large amount of friction heat will be generated, and if the mold is not well vented, the gas will burn and produce obvious black streaks (black spots);

8. When the barrel or glue head is worn, cracked and bent, the polymer part is overheated and produces black marks (black spots);

9. When the rubber ring is worn, the melt cannot advance smoothly and the material is extruded, which will cause excessive gas in the barrel, and when the injection is smooth, black lines will occur due to sharp friction;

10. The tolerance between the outer diameter of the rubber ring and the gap between the cylinder wall is too small, so that the screw melt produces a large resistance surface, resulting in friction heat and black lines (the outer diameter of the rubber ring can be disassembled and ground a few or replaced with new products with large tolerances to make the screw melt smoothly);

11. The eccentricity of the screw and the barrel produces a very large friction heat;

12. The compression ratio of the screw is too large, the groove of the feeding part is shallow, and the inner wall of the barrel and the raw material produce a large friction force, which causes the raw material to be overheated and decomposed, resulting in black lines (black spots);

13. The temperature is incorrect, the actual temperature of the heating sheet and the error of the thermometer are too large, and the temperature of a certain section is overheated and it is not easy to intuition, so it is necessary to use the measuring instrument to check.

三、Materials

1. The raw material itself has black spots;

2. The raw material bag is damaged or contaminated during transportation, handling and storage, and mixed with foreign substances;

3. The material is mixed with sundries during artificial proportioning or material making;

4. Some raw materials need to add lubricants, if the addition is insufficient, it will seriously produce friction heat, because too much exhaust gas is not eliminated in time, resulting in gas combustion and black lines (black spots);

5. The raw material itself has insufficient heat resistance and cannot withstand the operating temperature, and the raw material (additive) is pyrolyzed;

6. If the bag or storage bag is not clean, foreign matter may be mixed in when it is used again.

四、Other reasons

1. The production of different materials in the barrel for a long time, due to the change of temperature, oxidation, degradation, and the adhesion of various materials to the metal surface and other related factors, accumulated over time, resulting in the gradual formation of a carbonized layer on the surface of the screw, pipe wall, nozzle, etc., when encountering materials with higher viscosity, it is separated and gradually brought out. If there are scars or chips in the screw and pipe wall, it will be easier for the molten material to be retained, and when the machine is stopped and started frequently, the above problems will be more serious;

2. Crushing defective products, resulting in material confusion;

3. When changing materials, they are not cleaned up;

4. The floor product or runner material is directly put into the crusher;

5. The pulverizer has a scraper blade, and the material is not adjusted and controlled in time;

6. The shutdown method of special materials such as PP, PMMA, ABS is not accurate;

7. If the feeding method is wrong, such as adding black material and adding white material directly, black dust may fall into the white material due to static electricity or other reasons;

8. When cleaning the machine, the original low-temperature materials used in the discharge pipe are not completely replaced, and when the operating temperature rises, the low-temperature materials (fire-retardants, additives, etc.) are degraded by heat.