Canadian Plastics

Focus on Gas Assist Molding: No more bottles

Gas assist injection molding is a process enhancement to conventional injection molding that, properly implemented, can result in decreased cycle times, reduced scrap and less material usage. What man...

July 1, 2001   Canadian Plastics



Gas assist injection molding is a process enhancement to conventional injection molding that, properly implemented, can result in decreased cycle times, reduced scrap and less material usage. What many processors don’t realize is that these benefits can quickly be offset by the high cost of using nitrogen in compressed gas cylinders. To capture the full range of benefits of gas assist molding, processors should consider installing nitrogen generation equipment.

While virtually any size of operation running gas assisted molding processes can profit over the long term by using nitrogen generation, the return on investment is the fastest for companies consuming over 45,000 standard cubic feet (about 150 cylinders) per month. For these moderate to heavy users of gaseous nitrogen, switching from compressed gas to a nitrogen generation system can result in cost-savings as high as 90 percent, according to one estimate.

Everyday air we breath is composed of 78 percent nitrogen. Nitrogen generators work by taking in atmospheric air, compressing it to about 200 psi, processing it to remove moisture and hydrocarbons, then passing it through a series of separator membranes. The membranes are designed to allow the collection of nitrogen molecules, while permitting molecules with different molecular weights to pass through and vent off. Depending on the system, the nitrogen can then be stored, further cleaned and/or pressurized. Most membrane nitrogen systems can cost-effectively achieve purity levels of up to 99.5 percent.

One recent advance in the design of nitrogen generation equipment has been the development of oil-free, high-pressure systems. The NitroGenie, manufactured by Pacific Consolidated Industries and sold through Alliance Gas Systems, Inc., is an oil-free, self-contained machine that provides an adequate flow of clean air via a dedicated Ingersoll-Rand rotary feed air compressor, so there is no need to draw off your shop air compressor. The output air goes through four separate clean-up systems before entering a matched set of Praxair membranes. The unit separates the dry, hydrocarbon-free air into nitrogen and other gases by a pressure differential created across the membrane fibres.

An additional feature of the NitoGenie is an on-board oxygen analyzer that senses when specified nitrogen purity levels are reached. It signals a PLC to manage the output to provide purity (up to 99.5%) at a pre-specified setting. Nitrogen with purity less than specified is dumped.

“With this generator the purity of your nitrogen is never a guess,” says Steven VanHoeck, vice president of Alliance Gas Sytems, Inc.

The Gain Nitrogen Generation System, from Gain Technologies, has been developed to meet the demand for a continuous supply of high-volume, oil-free nitrogen. Features include a membrane module to produce the nitrogen, and air-driven intensification that provides stored nitrogen at up to 2500 psi and up to purity levels of 99.5%.

Two models, a 5 and 10 SCFM unit, are designed for continuous operation and require minimal maintenance. Each self-contained, portable unit is mounted on a single skid and requires only two or three air connections.

Alliance Gas Systems, Inc.

888-221-9699

Gain Technologies 810-254-9000


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