MAN’s straight-six cylinder engines are lighter and quieter due to the rigid one-metre-long rocker cover moulded of mineral-filled and glass fibre-reinforced polyamide from Rhodia Engineering Plastics.
The 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.
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 a high level of rigidity, while maintaining low values for shrinkage and warpage, according to Rhodia. 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 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 moulds.
Rhodia Engineering Plastics carried out structural analyses using the finite element method (Ansys) and also performed mould 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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