Increasingly, efficient molding is being defined as processes that combine as many functions and modules as possible in one operation. “Polyurethanes, with their freedom of design, make it possible to produce structures in a single shot without costly secondary finishing, even if the structures are complex with undercuts, ribs, and differences in wall thickness,” says Ulf-Peter Pestel, Managing Director of Pestel PUR-Kunststofftechnik GmbH in Chemnitz, Germany. “And the microcellular polyurethane RIM process contributes to cost reduction as parts become heavier, more complex and larger.”
The flame-retardant Baydur 110 mixture, produced by Bayer MaterialScience, is an example. This low viscosity, microcellular polyurethane integral skin foam ensures that remote corners of a mold are filled even at pressures as low as 10 bar. Metal connectors and other inserts can be molded in at the same time.
This material is used in the tailgate of the Jaguar field chopper produced by Claas Selbstfahrende Erntemaschinen GmbH in Harsewinkel, Germany. The tailgate is made at Pestel PUR-Kunststofftechnik in a single shot. The molding, which weighs 72.6 lb, has overall dimensions of 6.93 x 4.62 ft with a number of undercuts and ribs. The complex large-format moldings would not have been possible using other technologies.
The polyurethane specialists in Chemnitz used aluminum molds with multiple splits or split-ejector combinations. Aluminum molds are around 30% less expensive than equivalent steel versions. “The advantages of polyurethanes over conventional materials such as glass fiber-reinforced plastics and sheet molding compounds are particularly apparent when producing large-format moldings with a highly structured inner surface,” continued Pestel. Presently, Pestel PUR-Kunststofftechnik operates machines that produce polyurethane components with dimensions of up to 8.52 x 6.6 ft and weigh 176 lb.
Filed Under: Factory automation, Materials • advanced, Molding • injection molding components