The principle and advantages of gas-assisted injection molding

Gas-assisted injection molding has developed rapidly in recent years due to its advantages of low injection pressure, small warpage deformation of products, good surface quality, and easy processing of products with large wall thickness differences. It has been used for commercial plastic production in developed countries for almost 20 years. Gas-assisted injection molding includes two parts: plastic melt injection and gas (generally nitrogen) injection molding. Compared with the traditional injection molding process, gas-assisted injection molding has more process parameters to determine and control, so there are special requirements for product design, mold design and molding process control.

The gas-assisted injection molding process first involves underfeeding resin injection into the mold cavity, and then the high-pressure compressed nitrogen is introduced into the molten material, and the gas flows to the low-pressure and high-temperature areas of the product in the direction of least resistance. When the gas flows in the article, it hollows out the thick-walled section by displacing the molten material. These replaced materials fill the rest of the product. When the filling process is complete, the gas continues to provide the holding pressure to minimize shrinkage or warpage of the injected product.

Advantages of gas-assisted injection molding:

The low injection pressure reduces the residual stress, thereby minimizing warpage deformation;

The low injection pressure reduces the clamping force requirements, and small tonnage machines can be used;

The low residual stress also improves the dimensional tolerance and stability of the product;

Low injection pressure can reduce or eliminate the appearance of product flashing;

The thick part of the finished meat is hollow, thereby reducing plastic, up to 40%;

Compared with solid products, the molding cycle is shortened, less than half of the foam molding;

Gas-assisted injection molding greatly improves structural integrity and design freedom;

For some products with large wall thickness differences, they can be formed at one time by gas auxiliary technology;

Reduce the pressure in the mold cavity, reduce the loss of the mold, and improve its working life;

Reduce injection points, airways can replace hot runner systems and reduce mold costs;

Gas channels along rib plates and raised roots increase stiffness without having to worry about shrinkage marks;

Excellent surface finish, no need to worry about swirling phenomena caused by foam molding.

The use of gas-assisted injection molding technology allows designers to design products more complexly, while mold makers are able to simplify mold construction. The increasing functionality of the article and the reduction of the component of the product shortened the cycle time, eliminating the need for assembly and post-dressing work. In the production of molded CD trays and press-fit laminates for motor vehicle electronics centers, gas-assisted injection molding can be applied to the production of thin-walled products. Increased dimensional stability, reduced residual stress on the article and reduced warpage are a major advantage of gas-assisted injection molding technology. The application of gas-assisted injection molding technology will become increasingly complex and diverse. At present, gas-assisted injection molding technology can be used to produce products with quality from 30g~18kg.