MAN Engines run more quietly thanks to a specially designed rocker cover, molded in TECHNYL® polyamide from Rhodia

Freiburg, Germany, June 2nd, 2005 - The new straight-six cylinder engines from MAN Nutzfahrzeuge AG are not only compact and comparatively light, but they also run more quietly thanks to the very rigid one-meter-long rocker cover molded of mineral-filled and glass fiber-reinforced TECHNYL® A218 MT15 V25 polyamide from Rhodia Engineering Plastics.

This rocker cover features a smooth surface finish, but is heavily ribbed on the inside, which reduces resonance, and therefore excessive sound radiation. The cover is also attached to the cylinder head by means of acoustically decoupled mountings and sealed with a moulded elastomer seal.

The polyamide 66 used for the manufacture of the cover – TECHNYL® A218 MT15 V25, contains 15% mineral filler and 25% glass fibre. This combination gives the PA 66 its high level of rigidity, while maintaining low values for shrinkage and warpage and also good isotropic shrinkage characteristics as well. The material also features low creep tendencies, thus contributing to the long-term tightness of the cover seal.

Polyamide 66 grades are distinguished by a high resistance to chemicals, and to hot engine oil in particular. The particular Rhodia material chosen for this application is also heat stabilized. Other characteristic properties of polyamide which make it the emerging material of choice for rocker cover applications include its good flowability – necessary on account of the long melt flow paths and the many ribs in this particular application – and its high weld strength.

This new engine component is the product of a joint project between MAN Nutzfahrzeuge AG, the plastics processing firm of Elring Klinger GmbH, and the raw material manufacturer Rhodia GmbH. Elring Klinger was responsible for the entire project, including the design of the moulded part and the design and manufacture of the molds. Thanks to the vast experience and expertise of all involved, the specified requirements for this commercial vehicle engine component were quickly met.

As one part of its contributions to this joint project, Rhodia Engineering Plastics not only carried out structural analyses using the finite element method (Ansys) but also performed mold filling simulations (Moldflow) for optimizing the injection point with reference to shrinkage, warpage and filling behaviour. Additional Rhodia services included heat aging tests, thermal shock tests and leak tests using proprietary equipment in the company's modern, well-equipped laboratory in Freiburg.

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