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.
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