Gas assist molding is a low-pressure plastic injection molding process where pressurized nitrogen gas is injected into the mold, pushing the plastic into the mold extremities, while hollowing out thicker sections in the part.
In the gas assist molding process, the plastic material is melted and injected into the mold cavities via the conventional plastic injection molding process. Plastic material in contact with the mold walls begins to solidify first. As this happens, nitrogen gas is injected into the mold through strategically designed and placed gas channels, providing pressure that pushes the plastic material into the mold extremities. Once the plastic cures, the nitrogen is vented and the gas assist injection molded plastic parts are removed from the mold.
Less plastic material needed (material savings)
Reduced part weight (in some cases up to 40%)
Decreased cycle time
Increased part strength and rigidity
Reduced warpage and distortion
Improved part appearance (eliminates sink marks and surface blemishes)
Reinforces ribbed parts
Enables use of smaller plastic injection molding presses
In gas assist plastic injection molding, the pressurized gas follows the path of least resistance and displaces the plastic material in the thicker areas of the part, leaving hollow sections for reduced material use and part weight, yet not compromising part appearance or functional performance.
With gas assist molding, localized gas pressure within the mold results in better packing of the plastic which reduces warpage, shrinking, surface blemishes, sink marks and internal stress. Gas assist injection molded plastics generally make for stronger and more aesthetically pleasing parts.
The need for less plastic material and the consistent pressurization within the mold also enable gas assist injection molded plastics to cool faster, reducing cycle times and increasing plastic injection molding machine output – saving time and cost!
In gas assist plastic injection molding, the internal pressure provided by the nitrogen gas enables lowering the outer force needed to hold part shape, so large plastic parts can be produced with less tonnage on smaller plastic injection molding machines.