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September 1, 2003

4 Min Read
Fluid-assist molding


Gain Technology displayed an automotive IP core half that used its GAIM systems to economically reduce the use of expensive hot-runner manifolding in the tooling for the part.

Fluid-assist injection molding, or FAIM, is one of the latest names for gas-assist and water-assist technology. Engel demonstrated the latter in Chicago on a 165-ton/19.7-oz model of its latest Victory Tech Series tiebarless GP presses. A similar display was a big hit at K 2001.

Incredibly complex automotive cooling pipes were water-assist injection molded out of nylon—that’s right, hygroscopic nylon—in a single-cavity mold at 45-second cycles using Engel’s Watermelt system, which is now a standard option.

A three-plunger pump driven by a frequency-controlled motor in the Watermelt unit precisely controls the pressure and flow of the injected water. The unit has a built-in water treatment module to ensure water quality, and its control can be interfaced with the machine control.

Working in collaboration with German water-assist systems supplier PME Fluidtec GmbH, Krauss-Maffei offers WIT Powermodule 27/210 water injection units across the line of its C and MC Series molding machines. Water assist was also the highlight of the Cinpres Gas Injection booth.

Cinpres has also partnered with a German systems supplier, Stieler Kunststoff Services. Water assist was demonstrated at the Cinpres booth on a 198-ton, 8.7-oz Sumitomo direct-drive all-electric (Model SE180D) equipped with a Wittmann robot. Hollow core chainsaw handles were molded in 30 percent glass-filled nylon at 40- to 45-second cycles, said to be 30 percent faster than a similar part molded with gas assist.

  • Gas Is a Fluid, Too

    Wilmington Machinery has formed a partnership called Structural Gas Injection (SGI) with Alliance Gas Systems to develop gas assist and related technologies for its large-platen, multinozzle, low-pressure line of molding machines. SGI will provide turnkey solutions, including product/process development, product design support, tooling development, specially designed low-pressure/

    large-platen injection presses, and process controls for FAIM. By merging Wilmington’s versatile low-pressure molding technologies with Alliance’s gas-assist expertise, SGI envisions the creation of systems capable of molding parts weighing up to 200 lb, a machine that can run up to 4000 lb/hr of material, single- or multinozzle gas paths with independent injectors, and the use of multiple tools and processes in a single machine.



    Nylon automotive cooling pipes were water-assist molded by Engel on a 165-ton tiebarless Victory Tech press. The control on Engel’s Watermelt unit can be interfaced with the machine control.

    Gain Technologies’ Michael Ladney asks, Why use expensive sequential hot runners for molding large parts when you can save on tooling costs with the assistance of gas? At NPE Gain displayed an Audi A2 instrument panel core half insert, which was molded on a 2500-ton press in 60 percent glass-filled SMA to prove his point. It was previously run in 12-drop hot manifold tooling. Ladney put $50,000 of his own money into building a mold to prove that the part could run in a single-drop, gas-assisted tool without hot runners. His customer resisted that concept.

    But the part now runs in a mold with three-drop hot runner manifolding, and with gas assist. Gain reportedly eliminated six to eight weeks of the tool build time with the use of its systems, and saved up to $100,000 in outlays for hot runners.

  • Lowering Pressures

    Fully integrated turnkey nitrogen gas generators dubbed SNGII will be available from Bauer Plastics Technology Group for gas-assist molders this fall. They feature a modular design and are capable of supplying product gas at pressures up to 5000 psi. Costs start at about $70,000.

    Uniloy Milacron sources discussed the application of its first 2000-ton low-pressure molding machine in the gas-assist molding of 75-lb PP storm water chambers that are 50 inches wide and 7 ft long. The machine uses Uniloy’s multinozzle, low-pressure molding technology trademarked “Structural Web.”

    Stormtech (Old Saybrook, CT) molds the parts, a culmination of a four-year, $75 million-plus development effort between Uniloy Milacron and Stormtech’s parent company, Infiltrator Systems Inc., which led to the creation of the 2000-tonner. Using traditional high-pressure molding, it’s estimated that a 12,000-tonner would have been required to make such parts.

    Presma, like Milacron, did not bring any machinery to Chicago. Instead, it brought parts molded on its application-specific, custom-built, low-pressure molding systems run with or without gas assist. Presma also builds systems for structural foam, multimolding, crosslinking EVA, and plastic corks for wine bottles.

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