Gas Assist Injection Molding

Note: The following index list will take you to separate articles pertaining to the specific subject.

return to Plastic Information and Processes

Introduction:

Gas assist is an enhancement to the basic process of injection molding, and should not be considered a distinct and different process. The two most common methods are Gas Injection through-the-nozzle and Gas Injection via gas pins, or "in-article".

Process:

Gas assist processing is simply the injection of a second fluid into a partially filled tool cavity, much in the same way the two-shot process operates. In this case, the second fluid is a gas rather than resin. The gas injection phase completes the filling of the cavity, and packs the molded part more uniformly from internal channels, rather than from pressure points at the resin gate location. Gas distribution is controlled by resin distribution: if the resin distribution in the cavity does not facilitate the desired results, no changes in the gas injection phase can correct the problem.

Advantages

Increased output

Reduced resin consumption

Reduction of Design Constraints

Gas injection through the nozzle does not require the addition of hardware to the mold, and is quick for set up purposes.

Gas injection via gas pins, or "in-article" allows the injection of the gas at multiple points in a tool with differing pressures and time. In-article also allows for injecting at lower initial pressures as the injector will be located at a point in the flow channel where the resin is still molten.

Disadvantages

Gas injection through the nozzle will require a shutoff valve to isolate the gas from the injection barrel. Valves cost from $5,500.00 to $20,000.00 depending on the source and options.

Gas injection via gas pins, or "in-article" has a common problem of plugging of the injectors with resin.

Return to the Enginnering Resource Center Home Page. (ERC)
Kodak Equipment Manufacturing Division. (KEMD)

return to Plastic Information and Processes

Return to the Top