What’s so special about molding margarine tubs? The application may seem trivial on the surface, concedes Fakuma exhibitor Netstal (Näfels, Switzerland), but what lies underneath might be startling, according to Markus Dal Pian, Vice President, Sales and Marketing.
A slightly modified Netstal Elion Hybrid machine will be molding standard-format, 15-oz margarine tubs with in-mold labeling decoration in a cycle time of five seconds. Upon closer inspection, booth visitors will discover that the process is performed in a stack mold with 4+4 cavities. "The really revolutionary thing about the whole process is hidden from view: The polypropylene packaging is not injection molded but manufactured in an injection compression molding process," explains Dal Pian. "This combination of injection compression molding and stack mold is a complete novelty in the industrial production of packaging," he stresses.
The cavities are partially filled in only 100 ms with extremely consistent results, says Netstal, and the process is performed at a low pressure to prevent tension in the material. Parallel platens ensure 99.98% synchronicity between the mold built by Plastisud (Castelnaudary, France), the machine and the automation system designed by Machines Pagès (Foncine-le-Haut, France), claims Netstal.
Plastisud developed the stack mold specially adapted to the requirements of the new production process in just a few months. "The unique injection compression molding technology guarantees perfectly balanced parting planes with an extremely low dispersion rate" explained Laurent Buzzo, CEO of Plastisud. Thomas Iten, PAC application engineer at Netstal emphasizes: "The special design of the stack mold developed by Plastisud plays a key role in this application." The automation specialist Machines Pagès provides specific know-how in the area of handling systems for in-mold labeling (IML) to ensure that the automation process was adapted perfectly to the machine and mold.
“The combination of the injection compression molding process with a specially balanced stack mold is a genuine innovative leap,” says Iten, because the configuration uncompromisingly combines the advantages of the two technologies. The fundamental benefits of injection compression molding include narrow wall thicknesses and lightweighting, resulting in reduced unit costs. The process also minimizes distortion and improves dimensional accuracy in the end product, especially the lids, because less stress is placed on the material.
Benefits include increased productivity and a reduction in material costs by up to 20% as well as total flexibility in terms of shape, appearance and decoration of the manufactured part.
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