handles produced with nitrogen injection molding

Gas (nitrogen) injection molding

Gas (nitrogen) Assisted Injection Molding (also called GAIM), consists in introducing an inert gas at a high pressure inside the previously injected molten plastic mass in the mold. By injecting gas in the molten mass, a bubble that remains attached to the gas injection point, forms. Its pressure has to push the plastic material until it completely fills the cavity in the mold. The pressure on gas is maintained until the temperature for the extraction of the item is reached and it has to adequately compact the plastic material pushing it against the walls of the mold. Gas can be injected with needle nozzles inserted in the molds that allow to create in the same item one or more bubbles.


The gas injection process can be divided into 4 periods:

  1. Injection: molted plastic is injected in the mold
  2. Inflation: gas is injected at a higher pressure than the pressure used to inject plastic in order to obtain an hollow item. Gas can be injected during or after the injection of plastic
  3. Gas pressure: once the item is filled with gas, the pressure in the hollow part becomes “holding pressure”
  4. Extraction: once the cooling cycle is completed, gas pressure lowers to atmospheric pressure and gas can be eventually recovered. The item can finally be extracted from the mold.

Fields of application  

This molding technique can be used with all the major types of thermoplastic materials, amorphous and semi-crystalline other than additivated materials. Depending on the different characteristics of materials, different thickness on the solidified part can be obtained: semi-crystalline materials will allow thinner walls while amorphous material will ensure thicker widths.

Gas injected molding finds application in many different fields such as: automotive, household appliances, interior design, professional and consumer electronic and merchandise.


Apt for the production of components with both thin or thick widths, this technology allows a remarkable decrease in the weight of the item and in the molding timings, lowering the final price. In addition, it allows to eliminate shrinkage where there are ribs or significant variations on the thickness, without compromising the mechanical characteristics of the item. Moreover, it enables the making of one final piece for items usually made up of several parts, avoiding the following assembling operations.


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