Gas-Assist Moldings

There are different gas-assist injection molding (GAIM) processes. Other names exist that include injection molding gas-assist (IMGA), gas injection molding (GIM), or injection gas pressure (IGP). Most of the gas-assisted molding systems are patented. This review concerns the use of gas, however there are others such as water-assist injection molding. 

The processes use a gas that is usually nitrogen with pressures up to 20 to 30 MPa (2,900 to 4,400 psi). Within the mold cavity the gas in the melt forms chaimels. Gas pressure is maintained through the cooling cycle. In effect the gas packs the plastic against the cavity wall. Gas can be injected through the center of the IMM nozzle as the melt travels to the cavity or it can be injected separately into the mold cavity. In a 

As reviewed, the basic processes have many different fabricating systems. An example for IM is micromolding precision molding of extremely small products as small as one mm. Products usually weigh less than 20 milligrams (0.020g) with some even as low as O.Olg. Products are measured in microns and have tolerances of 10 microns or less. A micron (pm) is one-miUionth of a meter 25.4 pm make up one-thousandth of an inch. In comparison a human hair is 50 to 100 pm in diameter. A mil, that is about 25 times smaller than a micron, is one-thousandth of an inch. 

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Poly(ether imidejs (PEI)s are a particular class of PI which combine the high-temperature characteristics of PI but still have sufficient melt processability to be easily formed by conventional molding techniques such as compression molding, gas assist molding, profile extrusion, thermoforming and injection molding." ... 

Gas Assist molding for extra weight reduction and sink elimination. 

Orientation of polymer chains has been shown to have a major effect on component properties. The chain orientation at the end of fill of a component is diflferent from most other areas. Overflows have been used in various areas of the plastics industry to improve weld line strength and provide a more consistent gas channel in gas-assist molding. This study will investigate if the use of overflows to change the orientation of the polymer chains provides a more capable molding condition. 

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