Gas assisted injection molding

Gas assisted injection molding

What Is the gas assisted injection molding process?

Gas-assisted injection molding is an advanced form of injection molding that uses pressurized nitrogen gas to assist in the molding of plastic parts. It combines traditional injection molding techniques with the introduction of a gas (usually nitrogen) to help distribute the molten plastic resin within the mold more efficiently.

1. Process

The process begins similarly to traditional injection molding: molten plastic is injected into the mold. However, unlike conventional molding, the mold is not entirely filled with plastic.

Once the mold is partially filled, high-pressure nitrogen gas is introduced. This gas pushes the molten plastic to fill the mold cavities, ensuring even distribution and forming hollow sections within the part.

As the gas maintains pressure, the plastic cools and solidifies, retaining the shape of the mold.

After the part has solidified, the gas is vented from the part

The finished part is then ejected from the mold.

2. Advantages

Since parts can be produced with hollow sections, there’s potential for significant material savings and weight reduction

The gas ensures more uniform cooling, which reduces internal stresses and thereby decreases warping and sink marks.

Designers can achieve larger and more complex parts with uneven wall thicknesses, which might be challenging with conventional injection molding.

The pressure exerted by the gas often means the machine requires less clamping force, allowing for the use of smaller machines.

The cooling time can be shorter because of the more uniform wall thickness and the nature of the gas-assisted process.

The hollow channels created by the gas can act as structural reinforcements, providing rigidity to parts.

3. Advantages

Large parts like handles, bumpers, and dashboard components which benefit from reduced weight and enhanced strength.

Components such as handles, panels, or bezels which require a good surface finish and rigidity.

Products like garden equipment, toys, or furniture can use gas-assisted molding for producing large parts or those with complex geometries.

4. Considerations

Effective gas-assisted injection molding requires precise control over multiple parameters, including plastic injection volume, gas injection pressure, and timing.

Molds for gas-assisted injection molding may need specialized venting systems to release the gas and additional channels to guide the gas through the part effectively.

Not all polymers are suitable for gas-assisted injection molding. The material must withstand the high pressures of gas injection without degradation.


In summary, gas-assisted injection molding offers several advantages over traditional injection molding, especially for larger or more complex parts. It provides designers and manufacturers with additional options to achieve improved aesthetics, functionality, and cost savings. However, expertise is required to optimize the process and ensure high-quality outcomes.

Have Questions about Plastic Injection Molding?

Please contact us, and we shall be happy to answer them!