Gas-assisted injection (injection) molding, also known as gas injection moulding process, is a new injection molding process . It is one of the most important developments in the injection molding industry since the advent of reciprocating screw injection machines.
Gas-assisted injection molding process is an extension of injection molding,unlike 2 shot molding process. It is developed on the basis of injection molding technology and structural foam injection molding. it can also be considered as a composite of injection molding and hollow molding. In this sense, it can also be called "Hollow injection molding". The principle is to replace the resin pressure in the cavity with a relatively low-pressure gas during the pressure holding phase of the original injection molding.
Gas-assisted injection, unlike unscrewing mold mechanism, can be achieved by simply adding an air supply device to the existing injection molding machine. The gas supply device is composed of an air pump, a high-pressure gas generating device, a gas control device, and a gas nozzle. The gas control device uses a special compressor to continuously supply gas, and is controlled by an electronic control valve to keep the pressure constant. There are usually 3 levels of pressure. A set of gas control device can be equipped with multiple injection molding machines.To achieve this, whole gas injectino moulding process required closely connections.
The gas generally used is nitrogen. Gas pressure and gas purity are determined by the shape of the molding material and product. The pressure is generally 5 ~ 32MPa, the highest is 40MPa.