Gas-assisted injection molding

Gas-assisted injection molding is an innovative technology developed on the basis of traditional injection molding. .

GIM (Gas-assisted injection molding) was adopted in production  since 1980s.

It is currently widely used in Europe and North America, Japan and South Korea, and many manufacturers in China have also adopted this new technology.

The principle of gas-assisted injection molding is to inject high-pressure gas into the wall of thick-wall plastic parts.

this would get rid of the  restrictions of typical injection molding and foaming molding.

So it has incomparable advantages over traditional injection molding technology.

Compared with the classic injection molding , gas-assisted  can lower the weight of parts, speed up the cooling , reduce the clamping force and simplify the mold design, thus it will greatly reduce the cost.

In terms of product quality, it can eliminate surface shrinkage marks, reduce internal stress and warpage deformation.

and it also can improve the strength and rigidity without increasing the weight of the injection parts by designing ribs with air passages.

Gas-assisted molding generally includes several  steps, like melt injection, gas inject, gas pressure holding, gas recovery and part demolding.

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  • Gas-assisted injection molding process

Firstly, a preset viscous fluid, generally molten polymer, about 75%~95% of the mold cavity is injected from the gate, and then a non-viscous fluid with a certain pressure is injected into the mold through the gate, runner .

The gas, generally nitrogen, is injected into the cavity.

Due to the low melt temperature of the contact part with the surface of the mold, the melt temperature of the core layer at the thick wall part (such as  ribs) is high, and the viscosity is small.

The high-pressure gas pushes the melt to move towards the end of the mold cavity, thus pushing the hot fluid to fill the entire mold cavity and forming an air passage in the thick part .

It is mainly used in the production of pipe-like parts, large parts and parts with different thickness

Gas-assisted injection molding is widely used in many fields such as household appliances, automobiles, office supplies and other daily products.

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Compared with the traditional injection molding process, gas-assisted injection molding needs to consider more , such as gas pressure, melt pre-injection, hold time between melt and gas injection, gas holding time, etc.

Most thermoplastic materials can be injection molded with gas assistance, and crystalline materials such as polypropylene, polyamide and PBT resin are more ideal materials because they all have accurate melting point, low viscosity.

Raw materials shall be selected according to the requirements of product performance, such as rigidity, strength, performance , chemical corrosion resistance, etc.

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