When using abs plastic particles for injection molding, shrinkage not only affects the appearance of the product, but may also reduce its functionality and structural strength. To avoid this problem, it is necessary to comprehensively control multiple links such as raw material processing, mold design, and molding process parameter control. First of all, the pretreatment of raw materials is crucial. abs plastic particles easily absorb moisture in the air. If the moisture content is too high, steam will be generated when heated during the injection molding process, resulting in uneven local pressure, which in turn causes shrinkage. Therefore, the particles must be fully dried before use, placed in a dedicated drying equipment, and moisture removed under appropriate temperature and time conditions to ensure that the raw materials are in the best molding state. At the same time, it is necessary to pay attention to the dried raw materials to avoid moisture again. They can be stored in a sealed manner or taken as needed to ensure their stable quality.
Mold design is a key link in preventing shrinkage. The design of the mold's cooling system directly affects the solidification speed and shrinkage uniformity of the plastic. Reasonable cooling water channel layout should ensure uniform temperature distribution in all parts of the mold to avoid local overheating or overcooling. For example, for product areas with thicker walls, the density of the cooling water channel can be appropriately increased or the cooling water temperature can be reduced to accelerate the cooling and solidification of the plastic in this area and reduce the shrinkage deformation caused by slow cooling. In addition, the gate design of the mold cannot be ignored. The size, position and form of the gate will affect the flow and filling effect of the plastic melt. A larger gate size can extend the holding time so that the plastic can fully compensate for shrinkage in the mold; the gate position should be selected at the thicker wall of the product to ensure that the plastic melt can be filled smoothly and effectively compensate for shrinkage; different forms of gates such as pin-point gates and latent gates have their own advantages and disadvantages in controlling shrinkage, and they need to be reasonably selected according to product characteristics and molding requirements.
Precise control of injection molding process parameters plays a decisive role in avoiding shrinkage. Injection molding temperature is an important factor affecting the fluidity and shrinkage of plastics. If the temperature is too high, the viscosity of the plastic melt will decrease and the fluidity will increase, but the shrinkage will also increase during cooling; if the temperature is too low, the plastic melt will be difficult to fill the mold cavity, which is prone to material shortage or uneven surface. Therefore, it is necessary to accurately set the barrel temperature and nozzle temperature according to the characteristics of ABS plastic particles and product requirements to ensure that the plastic is molded in the best condition. Injection pressure and holding pressure are equally critical. If the injection pressure is insufficient, the plastic cannot fully fill the mold cavity, which will cause the product to shrink due to insufficient density; if the holding pressure is too small or the holding time is too short, the plastic that shrinks during cooling cannot be effectively compensated for shrinkage. Reasonable adjustment of injection pressure and holding pressure parameters, and continuous application of pressure during the cooling process of the plastic can effectively compensate for the gaps caused by volume shrinkage and reduce shrinkage.
The structural design of the product also has a significant impact on the shrinkage problem. During the design stage, it is necessary to avoid excessive differences in product wall thickness as much as possible. Uniform wall thickness helps the plastic melt to cool and shrink evenly, reducing deformation and shrinkage caused by uneven shrinkage. If wall thickness changes cannot be avoided, a gradual transition or the addition of reinforcing ribs can be used at the sudden change of wall thickness to improve the flow and shrinkage of the plastic. In addition, a reasonable design of the demolding slope can not only facilitate product demolding, but also alleviate the surface shrinkage deformation caused by demolding force to a certain extent. By optimizing the product structure design, the possibility of shrinkage problems can be reduced from the source.
The maintenance and care of the mold should not be ignored. The surface of the mold that has been used for a long time may be worn, scratched or blocked by the cooling water channel, which will affect the cooling effect and the molding quality of the plastic. Clean, polish and inspect the mold regularly, repair the worn parts in time, ensure that the cooling water channel is unobstructed, maintain the good working condition of the mold, and reduce the shrinkage caused by mold problems. At the same time, the key components of the mold, such as the gate sleeve and ejector, should be replaced and maintained regularly to ensure their accuracy and performance and provide stable conditions for injection molding.
The experience and skill level of the operator also have an important impact on avoiding shrinkage problems. Skilled operators can adjust the injection molding process parameters in time according to product characteristics and production conditions to deal with possible problems. For example, when it is found that the product has a slight shrinkage locally, the operator can make corrections by appropriately extending the holding time, increasing the holding pressure or adjusting the cooling time. In addition, the operator should also have the ability to perform daily maintenance and troubleshooting of the mold, and promptly discover and solve potential problems in the mold to ensure the smooth progress of the injection molding process.
Finally, quality inspection and feedback mechanism are important guarantees to avoid shrinkage problems. During the production process, a complete quality inspection system is established to promptly detect shrinkage problems of products through first-piece inspection, patrol inspection and finished product sampling. Professional testing equipment, such as optical measuring instruments and ultrasonic detectors, are used to conduct comprehensive inspections of product dimensional accuracy, surface quality and internal structure. Once shrinkage problems are found, they are quickly traced back to raw materials, molds, processes and other links, the causes are analyzed and targeted measures are taken to improve them, forming a closed-loop management from production to inspection and then to optimization, continuously improving product quality and effectively avoiding the occurrence of shrinkage problems.
