Lightweight DuPont plastic solves truck oil pan
Taking weight out of vehicles is a key route to reducing emissions and improving fuel economy—two of the most challenging goals occupying the automotive industry today. But there is an elegant solution.
Auto designers and engineers recognize that switching from metals to inherently lightweight plastics in many structural and functional components can dramatically improve the power to weight ratio of the latest vehicles, leading to greater efficiency and compliance with automotive CO2 emissions regulations.
Lightweighting opportunities don’t stop at passenger cars. Arguably there are even greater possibilities for taking weight out of heavy trucks and commercial vehicles, as the following example of the metals to plastics revolution demonstrates.
Fifty percent lighter
DuPont Performance Polymers and ElringKlinger AG recently made a significant contribution to the heavy truck industry’s drive for fuel efficiency and emissions reduction by developing a lightweight injection-molded truck oil pan of DuPont™ Zytel® polyamide resin. Developed for Mercedes-Benz, the oil pan is up to 50 percent lighter than aluminium, and can resist stone and gravel chip impact during the typical 1.5 million kilometer lifetime of a truck or bus engine. There is also a 2dB reduction in noise level compared to metal.
By using lightweight Zytel® polyamide resin, ElringKlinger AG has been able to make the oil pan lighter with no loss of strength, while integrating over a dozen functions that are not possible with metal, such as oil pick-up pipes and fluid level sensors.
“In 2013/2014, the Euro 6 emissions standard will launch a new generation of engines onto the roads. It imposes the same kind of strict emission limits for diesel as for petrol engines. This is why manufacturers are not only focusing on efficiently reducing exhaust gases, but also on lowering fuel consumption. With this in mind, they are pinpointing lighter weight components, in particular. The trend is toward oil pans made of polyamide 6.6 with a glass fibre content of 35 percent,” said Klaus Bendl, Head of R&D, Elastomer Technology /Modules Division at ElringKlinger AG, Dettingen/Erms, Germany.
The company selected a heat stabilized, lubricated grade of Zytel® polyamide, following four years of prototype production and more than 3,000 hours of endurance testing. This included shooting steel balls at oil pan moldings at speeds up to 80 km/h at the DuPont European Technical Center in Geneva, Switzerland, simulating on-road environments, and dispelling concerns about the strength and durability of plastic.
“There is also a significant improvement in acoustics, since the noise level is around 2dB lower than that of competing products,” says Bendl, citing another advantage that plastics have over metals by helping to make engines quieter, in compliance with Euro 6 noise emission standards.
Truck oil pans are much larger and more complex than those for passenger cars, holding up to 10 times the volume of oil, and they must be considerably more robust in order to withstand truck engine lifetimes averaging 800,000 to 1.5 million kilometres.
ElringKlinger has succeeded in meeting those tough performance demands by commercializing two large but lightweight oil pan modules of Zytel® for new Mercedes-Benz 4- to 6-cylinder diesel engines. They weigh only 4.5 kg and 6.3 kg respectively—up to 50 percent lighter than their aluminium predecessors—and contribute to improved fuel economy and reduced emissions.
Designing for plastic
The outstanding performance of the all-plastic oil pan was achieved by designing the part for plastic, instead of simply substituting plastic in a component designed for metal. This called for a different approach in which DuPont performed many of the tests to optimize processing and performance, and also to refine the design.
“We worked closely with ElringKlinger AG throughout the development phase, using comprehensive mold flow and FEA analysis, prototype testing and design optimization, and selection of the precise grade of Zytel® most suited to performing in harsh underhood applications involving high temperatures, vibration, stone impact and oxidized oil,” said Christoph Lange, account manager for DuPont Performance Polymers.
Processing behavior was an important consideration in ensuring that the project would be cost effective. “Through process testing, we were able to demonstrate the excellent flowability of Zytel®, a characteristic that enabled ElringKlinger AG to achieve fast set up and molding cycles. The low melt viscosity of DuPont polyamide flows easily into the complex thin section oil pan mold, allowing very precise tolerance control in such a large component,” said Lange.
The oil pans are produced at ElringKlinger AG at their new “Werk 2” injection moulding production facility in Dettingen/Erms, Germany, which is ramping up to full production of some 50,000 units per year. Beyond Europe, the company also plans to manufacture the polyamide oil pans at its facilities in Changchun, China, and Leamington, Canada.
In addition to supplying Mercedes-Benz, ElringKlinger AG has initiated similar oil pan projects with other truck OEMs to help them take weight out of a new generation of diesel and petrol engines in order to meet global emissions limits demanding reduced exhaust gases and lower fuel consumption. Lighter weight components in high performance plastics, such as DuPont™ Zytel® polyamide, are a key part of this challenge.