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CHICAGO—Husky Injection Molding Systems Ltd. (Booth S1982) is showing a PET preform injection molding press that cuts cycle times by 20-30 percent and is its first big-tonnage, two-platen machine. Husky's high-speed Index machine uses a rotating turret block that carries four sets of preform cores. The turret block is mounted onto the moving platen. It rotates on large roller bearings. As preforms are molded on each set of cores, the machine indexes through four independent positions, rotating the core through injection, cooling and part ejection out of the back side of the turret, which is open for easy access. The cores sequentially move through the positions.

Independent core halves of the mold, together with neck splits and the part ejection system, are mounted on the turret block. All cooling water, drive power and hydraulics are supplied to the rotating block. Mounted onto the stationary platen are the mold's hot runner and cavity plate.

Traditionally, preform cooling has taken place in the mold.

Husky actually developed, and patented, a turret concept in the 1980s, according to a technical paper Michael Koch, vice president of technology, presented in April at the Bev-Pak Americas '97 conference in Fort Lauderdale, Fla. Husky officials revived the technology and improved it during the past year and a half.

At NPE, Husky is showing a 48-cavity Index system. Future plans call for machines with both larger and smaller numbers of cavities. Cycles times are cut 20-30 percent because cooling no longer takes place in the core or the cavity, so the mold can be opened faster after injection, Husky said.

Husky said the Index system molds preforms on a cycle of 14.8 seconds, vs. about 22 seconds on a standard 96-cavity mold. Husky cycle times will come down even more as the process is refined, the company said.

Husky also said Index technology allows reduction in clamp tonnage and the size of the machine. The Index machine can run a 48-cavity mold on a 250-ton press; normally, 300 tons of clamping force are required.

Husky's Index machine takes up only 55 percent of the space of a press normally used to run a 48-cavity mold, and 43 percent of a 96-cavity system.

The technology also improves quality because the machine can run at lower pressures and times for the injection and hold portions of the cycle, and the melt sees less residence time, Husky said.

Besides preforms, Husky said Index machines are suited for molding closures.

The injection unit is the same one used on Husky's new G-Series.

Husky will continue to manufacture traditional PET preform systems, from two to 96 cavities.

NPE 1997 also marks Husky's entry into two-platen injection presses, as the firm shows a 1,000-ton Moduline E-Series press making a 22-gallon container. Husky is making the hydromechanical-clamp E machines in clamping forces of 1,000-4,400 tons.

For big-tonnage machines, the two-platen trend started at K'95 in Germany two years ago. Michael Urquhart, vice president of sales and service for the Americas, thinks it's a permanent change.

``Two-platen machines are shorter and less-expensive to build. Our feeling is other people were on the market first, but we think we have come up with a design that has overcome some of the weaknesses, such as rigidity and platen parallelism,'' he said.

On the E machines, both platens use Husky's Reflex design, which maintains parallel platens by internally transmitting clamp forces from the tie bars into the molding areas to compress the platens, instead of deflecting them, which can cause problems.

Tie bars are mounted on the fixed platen, instead of the moving platen, to reduce moving masses and eliminate added weight from the tie bars.

In other NPE news, Husky:

Introduces an arm that allows its Moduline Top Entry robots to carry custom-designed, end-of-arm tooling to serve stack molds.

Introduces a two-stage G-Series packaging machine in clamping forces of 330-825 tons.

Is showing new hot runners for small parts. The 250 Series of nozzles has diameters of less than 10 millimeters.