Is injection molding the same as injection compression molding?

1, Principles and Process Flow
Injection molding: Injection molding, also known as injection molding, is a process of injecting molten plastic into the mold cavity under high pressure through the screw or piston of an injection molding machine, and obtaining the desired shape of plastic products after cooling and solidification. The process flow of injection molding mainly includes steps such as preheating, melting, injection molding, cooling, and demolding of plastic particles. During the injection molding process, the mold cavity remains fixed, and molten plastic is injected into the mold under high pressure. After filling the cavity, it cools and solidifies, forming a plastic product.
Injection Compression Molding (ICM) is an advanced form of traditional injection molding. Unlike injection molding, injection compression molding allows the mold cavity space to be automatically adjusted as needed during the injection molding process. Before the material is injected into the mold cavity, the guiding part of the mold is slightly closed, and the cavity space is expanded to twice or more of the finished wall thickness of the part. After the molten plastic is injected into the mold cavity, the movable part of the mold begins to push and close, compressing the polymer inside the cavity while maintaining an appropriate compression state to compensate for material shrinkage. The process flow of injection compression molding includes steps such as preheating, melting, injection molding, mold compression, cooling, and demolding of plastics.
2, Product features and advantages
Injection molding: Injection molded products have the characteristics of precise size, high surface smoothness, and complex structure. Due to the high-pressure injection of plastic into the mold during the injection molding process, it is possible to produce plastic products with complex shapes and precise dimensions. At the same time, injection molded products have high surface smoothness and can be used directly without further processing. In addition, injection molding is suitable for various thermoplastic materials, with a wide range of material choices to meet the needs of different products.
Injection compression molding: Products produced by injection compression molding have a higher flow length ratio (i.e., the ratio of flow length to wall thickness), lower internal stress, and higher processing productivity. Due to the automatic adjustment of the mold cavity space during injection compression molding, the polymer is kept in an appropriate compressed state inside the cavity, thereby reducing internal stress in the material and improving the dimensional stability and mechanical properties of the product. In addition, injection compression molding is also suitable for products made of various thermoplastic engineering plastics, such as large-sized curved parts, thin-walled parts, miniaturized parts, and parts with good impact resistance requirements.
3, Application areas and cost-effectiveness
Injection molding: Injection molding is widely used in fields such as automotive parts, household appliances, daily necessities, medical equipment, toys, etc. These fields have high requirements for the dimensional accuracy, surface smoothness, and structural complexity of plastic products, and injection molding can meet these requirements. Meanwhile, injection molding has the advantages of high production efficiency and relatively low cost, making it occupy an important position in the plastic products industry.
Injection compression molding: Injection compression molding is mainly used in product fields that require higher flow length ratios, lower internal stresses, and higher processing productivity, such as laptop casings, car tailgates, car dashboards, and relatively flat car mudguards. These products typically have large sizes and complex shapes, with high requirements for material flowability and formability. Injection compression molding improves product quality and production efficiency by adjusting the cavity space of the mold to maintain an appropriate compression state of the polymer inside the cavity. However, due to the high cost of injection compression molding equipment and molds, its application range is relatively limited.
4, Differences and Similarities in Craftsmanship and Suggestions for Selection
Although injection molding and injection compression molding differ in principle, there are also some similarities between the two in terms of process flow, product characteristics, and application fields. For example, both require injecting molten plastic into the mold cavity, cooling and solidifying it to obtain plastic products; Both are applicable to the molding of various thermoplastic materials; Both are widely used in fields such as automotive components and household appliances.
However, there are significant differences between injection molding and injection compression molding in terms of process details and product characteristics. Injection molding is mainly suitable for producing plastic products with complex shapes, precise dimensions, and high surface smoothness; Injection compression molding is more suitable for producing products with higher flow length ratios, lower internal stresses, and higher processing productivity. Therefore, when selecting molding technology, comprehensive consideration should be given to the specific needs and process conditions of the product.
For products that require high precision, high surface finish, and complex shapes, injection molding is a more suitable choice. For products that require higher flow length ratio, lower internal stress, and higher processing productivity, injection compression molding can be considered. At the same time, factors such as the cost of molding equipment, production efficiency, and the design and manufacturing of molds also need to be considered.