The first application of a new long-fiber injection molding technology is the hull of a personal watercraft that will hit the market this summer.
The new technology produces a lighter, more efficient hull, according to Yves Carbonneau, engineering director at Camoplast, a privately owned company based in Sherbrooke, Quebec.
In the new process developed jointly between Camoplast, Bayer MaterialScience and Krauss-Maffei, long glass fibers are injected along with polyurethane resin in a one-step process. A fiberglass chopper is attached to the polyurethane-dispensing mixhead, which connects to a robot. The robot is programmed to move over the open mold cavity while simultaneously dispensing both the long glass fibers and the polyurethane resin in an open-pour method. At the end of the pour, the mold is closed to form the part in a low-pressure process.
The goals of the project are to achieve a superior Class A finish, reduce part weight without sacrificing strength, and keep costs down.
"Because this particular customer had used glass-reinforced polyester resin for years, initially there was skepticism that making such a big leap to a new material, polyurethane, and a new technology would result in high performance and great aesthetics," says Carbonneau.
Bayer MaterialScience developed a proprietary grade of its Baydur STR 814 polyurethane system, which features a 60-second open time compared with a traditional open time of roughly 10 seconds. This facilitates the flow of the material and reinforcing glass into tight spaces, making it possible to design in strengthening ribs, and other features that can boost the effectiveness of the hull.
KraussMaffei enhanced its long-fiber processing technology by nearly doubling the glass output capability from 180 g/sec to 300 g/sec, enabling the production of the highly reinforced structural parts.
Camoplast reaped other benefits, as well, by switching to CLF and the Baydur STR 814 system. Polyurethane is a more environmentally friendly alternative to other types of resins like polyester, which contains VOC-emitting styrene that is a hazard to both the environment and machine operators. In addition, using polyurethane and CLF allows for faster, more automated production and a smaller manufacturing footprint, which are advantages in both cost-effectiveness and safety.
Because polyurethane is less dense than polyester the hull produced with the new process weighs 25 percent less than the previous hull.
"The hull of a personal watercraft is the largest and most vulnerable part of the vehicle. As it breaks over waves there is the chance that it could crack," says Carbonneau. "The part must have the best structural and mechanical characteristics while remaining lightweight for high performance. By using a light material, the Baydur STR 814 system, reinforced with molded-in ribs, we achieved the necessary strength to withstand big waves and other safety issues that are inherent with a personal watercraft."
Camoplast uses a nickel shell mold, which is less costly than the steel mold needed in the sheet molding compound process. And by using in-mold coating technology, Camoplast is able to produce a painted, Class A surface right out of the mold, eliminating costly and time-consuming secondary painting operations.