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The purpose of gas-assisted injection molding is to prevent and eliminate sink marks and shrinkage warpage on the surface of the product, improve the surface properties, and make the surface of the product smooth. Gas-assisted injection molding process can be divided into four stages: the first stage is melt injection, that is, the molten plastic melt is injected into the mold cavity, it can be divided into "short injection" and "full injection" . The second stage is gas injection. Gas can be injected at the beginning, middle and later stages of the injection period. The pressure of the gas must be greater than the pressure of the plastic melt to achieve a hollow state of the plastic part. In the third stage, the gas pressure is maintained. When the interior of the plastic part is filled with gas, the part is cooled while maintaining the air pressure. During the cooling process, the gas is pressed from the inside to the outside, so that the outer surface of the plastic part closely adheres to the die wall and passes through. The secondary penetration of gas replenishes the internal volume shrinkage brought about by cooling. The fourth stage is demoulding the parts. With the completion of the cooling cycle, the gas is discharged and the plastic parts are taken out of the cavity. Gas-assisted molding of plastic parts can be roughly divided into three categories: tubular and rod-shaped articles such as clothes racks, armrests, backs, brush sticks, and steering wheels. They mainly use gas penetration to form the air passage to save materials and shorten the molding cycle. Plate-shaped parts such as automobile dashboards and office furniture are mainly to reduce warpage and tonnage requirements for injection molding machines, as well as to improve the rigidity, strength and surface quality of parts; uneven thickness and intricate parts such as household appliances Shells, automotive parts can be simplified by one process.