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එන්නත් නිෂ්පාදනයේ කළු ලප විසඳන්නේ කෙසේද?

කාලය: 2019-12-12 වැදුම්: 30

Black spots and impurities are characterized by small particles and dark brown, and generally do not reflect light. When the particles are large, the impurities are layered, brittle, brittle, and porous after being broken. Their distribution has two characteristics:


1. Some wholes are scattered randomly, some are scattered randomly, and sometimes only occasionally appear in a local area


2. Such black spots and impurities sometimes only appear on the surface of the product, and sometimes there are no matter the depth of the surface.


It is interesting to associate these two points and find that the impurities appearing only in a certain local area must be the black spots on the surface layer, and the distribution of black spots, regardless of the depth of the surface, must be an overall random scattered distribution. This is because the impurities existing inside must exist before molding, and the impurities appearing only during molding must be distributed only on the surface.


Black spots and defects of impurities are the most important factors that cause the rejection rate in the normal production process. It mainly affects the appearance of the product and leads to scrap. Impurities and most of the black spots are foreign substances, which have nothing to do with the raw material itself, and a small part of the black spots and impurities are caused by the raw material itself.


Causes of black spots and impurities before molding

1. During raw material processing, due to various reasons, foreign matter is not clean and black spots appear on the raw material;


2. Impure granulation causes black spots;


3. The raw materials are mixed into the color masterbatch or speckled crushed blocks and scraps;


4, the material is not pure, low melting point material is mixed with high melting point material;


5. Impurities may appear during packaging, transportation, and storage. Its obvious feature is that after the raw materials are unpacked, if you observe carefully, you can see that there are foreign matter and impurities on the surface of the material particles.


6. The impurities and foreign materials in the feeding process .


Except that 5 will not directly cause pollution to the hopper material, other parts may contaminate the raw materials during the loading process, causing black spots and impurities in the product.


Pollution sources include: dust, suspended matter in the air, foreign material scraps, foreign material grains, powdery color masterbatches, dyes, etc. In order to prevent black spots caused by foreign matter and impurities, management must be strengthened to control all links (including the reuse process) from the entry of raw materials to the plant. When changing materials, you must carefully clean up the places where the original materials or crumbs may be trapped, especially the storage box, hopper, funnel, and hem clip fastening. In normal production, special attention should be paid to the feed source-the cleaning of the storage box. After the production is stopped, the feeding system should be sealed to the outside environment, the feeding port of the feeding pipe is sealed to prevent contamination, to achieve interlocking and closed management.


7. The raw material is carbonized. Such black dots are generally large in size, and the appearance diameter of large black dots can reach 1-2 mm. Most "black dots" are thicker, and there are one or two layers thinner. In this case, the raw materials are accumulated for a long time or are locally heated, decomposed, coked, and carbonized into agglomerates. It is formed by shearing and breaking the flow in the screw or nozzle.




1. For molding impurities, black spots are formed due to foreign materials mixed in the material, and the cleanliness of production, packaging, storage, transportation, opening, mixing and mixing to the barrel must be strictly controlled.


2. For carbonized black spots, the processing temperature should be strictly controlled. In actual production, it means that there is a difference between the processing temperature and the actual processing temperature. For the same equipment, different back pressures, different cycle times, different one-time injection quantities, and different thermocouple insertion positions will cause different carbonization and degradation trends at the same processing temperature. Specifically, when the temperature is the same, the back pressure is small, the cycle is short, and the amount of one-time injection is large. When the thermocouple is inserted in the upper part of the screw barrel, the melt drop / decomposition tendency is weak, and it is difficult to generate carbon black spots. To prevent carbon black spots, we must also prevent material accumulation. We must eliminate dead corners in the screw barrel, nozzle, and flow channel, make a smooth transition at the turn, and eliminate areas where material may be trapped.


3. For the black spots of the additive degradation deposition or the existing carbonized material deposited on the thread surface and the screw barrel wall. Generally with the production, these black spots will be released from the original adhesion surface into the molten material under various strong shearing effects in the screw barrel. This "discharge" process is a process in which black spots and impurities appear in the product. For example, in the process of transferring materials and changing colors, this "discharge" impurity process is inevitable, and we must try our best to shorten this process. It's "cleaning." The following are two cleaning methods:


1) Clean the screw by shooting to the air (shot to the air after charging).


2) Melt into the injection table, melt into the air, and then melt into the injection table, glue to the air. Repeatedly, the practice proves that the back pressure plays a large role in cleaning, and the melt and the screw are strongly sheared. . The melting speed is slow, so the melting time is also long. This effect is good, and foreign bodies are cleaned quickly. Note: There is a principle for back pressure at no time-as high as possible, so high that the screw barrel will not automatically heat up.


3) For the black dots during molding, the black dots must be attached to the surface of the cavity first, and then be fixed on the surface of the product by the molten material. Therefore, this method of removing black dots will prevent it from being in the cavity. For the determination of the mold with poor material, the cause and location must be determined first. For all the cavities that have relative movement, the mold core including the slider, neutron, and thimble / block may be burned. After the burn is determined, the damaged part should be repaired, and the friction of the sliding part should be reduced, and lubricating oil should be added.


In addition, to reduce the relative movement speed of the sliding part, such as advancing / retracting, opening and closing the mold, the slider should be moved as slowly as possible, rust and other stains between the slider and the template, the slider should be removed, rust and other Remove the stains and tie the nozzle tightly. For oil or water splashing on the smooth molding surface of the mold cavity, the black spots should be wiped frequently to the oily and water-prone areas to prevent its appearance on the molding surface.