Netstal, at Fakuma 2015 in Germany, showed what company officials said is a world first: Injection/compression molding on a stack mold.
During the show, a Netstal Elion press was molding a margarine tub from polypropylene, on a four-by-four-cavity stack mold. The 15-ounce tub weighed only 10.7 grams.
The mold cavities are partially filled in just 100 milliseconds, at a low pressure to reduce molded-in stresses. Then at the final stage, the clamp compresses closed over the last 2 millimeters or so.
Netstal claims the process reduces material savings by 20 percent.
The cycle time is 5 seconds.
Thomas Iten, packaging application engineer at Netstal, said the benefits of injection/compression molding include narrow wall thicknesses and a lighter product, for lower unit costs. Also, the end product — especially lids — show fewer signs of distortion and have greater dimensional accuracy, because of lower stresses placed on the melt.
French mold maker Plastisud developed the stock mold for the production process in just a few months. “The unique injection compression molding technology guarantees perfectly balanced parting plants, with an extremely low dispersion rate,” said Plastisud CEO Laurent Buzzo.
The injection/compression process goes on internally, out of sight. But at Fakuma, eyes were drawn to the automation system from Machines Pages, including in-mold labeling and also a rapid-fire robot especially designed to stack the tubs.
Netstal, based in Nafels, Switzerland, is part of Munich-based KraussMaffei Group.
The U.S. operation, Krauss-Maffei Corp. is in Florence, Ky.
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