Plastics Technology Group

About Gas Assist Injection Molding

Gas Assist Injection Molding is a low-pressure process utilizing nitrogen gas to apply uniform pressure throughout the molded plastic part.

By displacing molten plastic from thicker sections of the part toward areas in the cavity that are last to fill, nitrogen gas pressure creates channels within the part. Through the gas channels, pressure is transmitted evenly across the part, eliminating warpage, sink marks and internal stress. As a result, reductions in clamp tonnage, cycle time, and part weight are realized while the strength and rigidity of the part is increased. Gas Assist Injection Molding allows molders the freedom to design plastic parts without the restrictions limitations inherent to conventional molding.

Thin wall parts with heavy ribs, bosses and gussets are formed to high standards of flatness without sink marks or long cycle times. Long shapes are produced without multiple drops or hot runner systems, eliminating knit lines and lowering tooling costs. Multiple parts with complex design and differing wall thickness are molded as a single part without defect. Clamp tonnage requirements are dramatically reduced by 50% or more in most gas assist applications.


This part was originally molded in structural foam. With gas assist we were able to reduce the shot weight by 1 pound, reduce cycle time by 34%, and limit the paint process to 1 coat.

Thick sections can be cored out with gas assist reducing part weight and cycle time.

Thin wall parts can be molded warp free, without sinks, and with fewer gates.

Heavy ribs and bosses can be incorporated in your design without fear of sinks on the part surface. The ribs may actually be thicker than the nominal wall.

Thick handles are hollowed out with gas thus reducing part weight and cycle time. Critical dimensions are held to closer tolerances.

Large parts such as this headlight mounting module, can be molded with a single cold sprue, thus eliminating costly hot runner systems. Clamp tonnage is also greatly reduced so you use less energy, and smaller molding machines may be used.