High-gloss injection molding

High-gloss injection molding technology, also known as rapid thermal cycle injection molding technology, can use this technology to copy any shape on the surface of the mold well, so that the surface of the product has no melt marks, no flow marks, no streamlines, no shrinkage marks; The surface is high-glossed to achieve a mirror effect; Improve the strength and surface hardness of plastic parts; Thin-wall molding improves injection fluidity, product quality and strength; The injection cycle of thick-walled molding can be reduced by more than 60%; There is no need for subsequent spraying process with serious environmental pollution, which can reduce the process flow and save energy and materials. Directly reduce the cost of plastic products, protect the environment and the personal health of operators. It has a wide range of application prospects in home appliances, automotive communications, daily necessities, medical and other industries. For example: flat-screen TVs, computer LCD monitors, air conditioners, car interior parts, etc.
The process principle is: the mold is heated before the mold clamping and the stage mold process, and after the table mold is completed, the temperature reaches the set conditions and injection. The mold continues to maintain high temperature during the injection process, which can keep the rubber material in good fluidity during the mold filling process. After the injection is completed, when the pressure is cooled, the mold is cooled, and the cooling time of the product can be greatly shortened, thereby improving production efficiency.
The traditional method is to use a mold temperature machine to heat the mold. But the disadvantages of this approach are as follows:
1. It cannot meet the needs of rapid heating and rapid cooling in high-gloss injection molding;
2. The heating amplitude is small, and the welding marks on the surface of the product can only be reduced but cannot be eliminated;
3. Because the higher the hardness of the plastic, the worse the fluidity. Therefore, the hardness of the surface of the product using this process can only reach the HB level, which cannot meet the actual use needs;
4. The mold expands when it is heated up, and it shrinks when it cools down, making the clamping force very unstable. It is easy to cause various defects such as product dissatisfaction, burning, and large internal stress.
The steam high-gloss injection molding technology developed on the basis of this process has been improved for the above defects
1. This technology boils the water pipe in the mold, steam when it needs to be heated, cold water when it needs to be cooled, and the residual moisture is blown out with compressed air after cooling to ensure rapid heating and cooling
2. To eliminate the welding mark clip to the greatest extent. Water lines and glue shortage and other product failures
3. In the heating range, the use of H or even 2H hardness grade plastics, so that the surface hardness of the product is greatly improved
4. Since the pipeline is opened inside the mold, only the inner surface of the mold is heated or cooled, and the overall expansion of the mold is small, so the various product defects caused by the instability of the clamping force are reduced.
To produce high-quality high-gloss products, injection molding machines, molds, temperature control equipment, special plastics for high-gloss products, as well as boilers, cooling devices and other aspects are required.
1. Configuration of the plastic machine:
(1) The rigidity of the clamping mechanism should be good; Because the whole production process has to constantly heat up and cool. Therefore, the clamping mechanism of the injection molding machine must be rigid and strong to ensure the accuracy and stability of the clamping force. So as to ensure the surface quality of the product
(2) Choose an injection molding machine with large mold locking: When using this process, because gas-assisted injection can no longer be used, the clamping force required for the production of products will be relatively large.
(3) Choose a smaller amount of injection according to the situation: such as the production of flat-screen TV machines, LCD screen frames and other products, do not need a larger amount of injection, try to choose a small amount of injection molding machine when choosing an injection molding machine. The actual weight of the product is the best between 30%~80% of the theoretical injection volume of the injection molding machine. If the amount of glue injection by the machine is too large, the rubber material stays in the barrel for a long time and is easy to decompose separately, and defects such as silver wire will occur on the surface of the product.
(4) Equipped with a special screw to produce high-gloss products, the plastic hardness is high, and its melting index is relatively low, so the screw plasticization is required. At the same time, the shear of the screw should not be too large, otherwise the rubber will be easy to decompose.
2 mold configuration:
(1) The inner surface of the mold requires a very high finish to ensure the surface quality of the product
(2) The pipeline opened inside the mold must be reasonable to ensure that it can be heated up and cooled quickly
(3) The pipe inside the mold should have good thermal conductivity
(4) Due to the need for constant heating and cooling during the production process, the steel selected for the mold should be good.
(5) Pay special attention to the maintenance of the mold during use to ensure dryness and dust-free.
3 Configuration of temperature control equipment:
(1) The temperature control should be very accurate, which is an important guarantee for the quality of the product;
(2) The response of temperature control equipment should be very fast to ensure high production efficiency.
4. Special plastics:
When producing products with high surface quality, commonly used plastics are ABS, PC+ABS or PMMA+ABS. Among them, ABS has the lowest hardness, and PMMA+ABS has the highest hardness, up to H, or even 2H. But the higher the hardness, the lower the melting index. The fluidity deteriorates, so the appropriate plastic can be selected according to the production needs.
Steam non-marking high-gloss injection molding technology is still an advanced production process in China. Because this technology greatly improves the surface quality and surface strength of the product, and can cancel the subsequent spraying or painting and other processes, not only protect the environment and the human health of the operator, but also reduce the process flow, save expensive secondary processing costs, while greatly reducing production costs, saving energy and materials.
With the increasingly widespread application of plastic parts, and people's awareness of environmental protection and safety gradually increasing, steam non-marking high-gloss injection molding technology will become another brilliant new star in the field of injection molding technology in the future.