First, the mold:

· Prenatal degreasing inspection can effectively prevent oil and rust stains from being mixed into the crushed material and be used (especially during the production process rather than during the initial trial);

• Mold gates that are too small or rough will produce a lot of frictional heat. If the mold is poorly vented, it will cause the gas to burn to produce significant black streaks (dark spots);

Second, equipment:

·Dryer motor operates for a long period of time, filth, and must be regularly cleaned;

·Dryer filters must also be cleaned and replaced on a regular basis. Otherwise, foreign matter will enter or the material will discolor and clump due to poor ventilation;

• The dryer is not fully sealed due to operator negligence or lack of operating equipment, resulting in the entry of dust in the air; or flying dust, contaminating the surrounding products and materials in the grinder; or the cartridge is too large to operate It is not easy to ignore the dead angle (feed pipe and its interface) and other factors, resulting in the cartridge is not completely clean during refueling;

·Long-term production operation, usually does not make 6S and its protection, the device has dust, resulting in mixed

• The shredding machine is not in place, resulting in contamination and contamination of other materials;

· The crusher is isolated from black and white as much as possible;

· Too small nozzle aperture or rough inner surface will generate a lot of friction heat. If the mold is exhausted badly, it will cause gas combustion to produce obvious black stripes (black spots);

• When the barrel or plastic head wears, when the cracks are bent, the polymer partially overheats and produces black lines (dark spots);

• When the apron part is worn, the forward movement of the adhesive cannot be smooth, and the phenomenon of squeezing causes excessive gas in the material tube. When the injection is smooth, black lines are generated due to rapid friction;

· The tolerance of the outer diameter of the apron and the clearance of the cylinder wall is too small to make the large resistance surface of the screw melt produce friction heat and lead to the generation of black lines. (You can remove the outer diameter of the apron and remove a few small ones or replace the new one with larger tolerance. Make screw smooth melt glue);

· The eccentricity of the screw and the feed tube generates very high friction heat;

· Screw compression ratio is too large, the feed part of the groove is shallower, and there is a large friction between the barrel inner wall and the raw material, which causes the raw material to overheat and decompose and produce black lines (dark spots);

• The temperature is not correct, the error of the actual temperature and temperature of the heater is too large, and the temperature of a certain section is overheated. It is not easy to intuition, and it needs to be checked with a measuring instrument.

Third, other:

·For a long time production of different materials in the barrel, due to temperature changes, the resulting oxidation, degradation, and various materials on the metal surface adhesion and other related factors, over time, resulting in the screw table, wall, nozzle, etc. At the same time, a carbonized layer is gradually formed. When a highly viscous material is encountered, it is separated and gradually brought out. In addition, if there are any scars or gaps in the screw and the wall, it will be easier for the molten material to stagnate and stop the power on. Frequently, these problems will be aggravated;

· People who do not understand materials smash off defective products, leading to material confusion;

· The defective product is confirmed by the technician to be crushed or abandoned;

· When replacing materials, for ease of operation, only the air gun blows away the remaining chips, but this method can not clean the barrel thoroughly; or use air guns to bang and blow at the scene, causing dust to permeate the entire workshop;

· Drops or runners feed directly into the crusher;

· Unscrupulous goods are smashed when they are casually blown with a blower;

· When handling products in the red box, pour directly into the crusher;

· When dealing with foreign substances, only one reason was found to have found all the real reasons;

· Pulverizer has a doctor blade phenomenon, there is no timely adjustment and control of the material;

· Stopping methods for special materials such as PP, PMMA, ABS;

· The feeding method is wrong. For example, adding black material directly to add white material may cause black shavings to fall into the white material due to static electricity or other reasons;

· When the washing machine did not completely replace the original use of low-temperature materials in the feed pipe, when the operating temperature increases,

As a result, low-temperature materials (fireproofing agents, additives, etc.) cannot withstand this temperature and are thermally degraded.

The situation usually occurs at the nozzle (especially during the production process rather than during the initial trial);

Fourth, materials:

· The raw material itself has black spots, and the ratio of this black spot exceeds the allowable range of the customer's incoming inspection or the allowable standard of the finished product;

• The raw material bag is damaged or contaminated during transportation, handling, storage, and is mixed with foreign matter;

· Materials are mixed with artificial materials or materials.

· Some raw materials need to add lubricants, if not enough, it will generate a serious friction heat, because too much exhaust gas is not removed in a timely manner, causing gas combustion to produce black lines (black spots);

• The raw material itself is not heat-resistant and cannot withstand the operating temperature. Raw materials (additives) are pyrolyzed;

· The material bag or the storage bag is not clean, and when used again, foreign matter is mixed in;