Evaluation of cam and roller surfaces and their manufacturing process by functional characterisation

Paper in proceeding, 2008

Friction and wear are constant problems encountered in camshaft development. The contact between roller and cam is a mix of sliding and rolling which leads to a wide range of failure modes. The uniqueness of this contact is also due to variations all around the cam of a multitude of parameters. A previous study described surface topography as a function of cam shape. The different types of wear mechanisms are strongly linked to contact pressures which are also dependent on roughness. The aim of the paper is to evaluate the quality of camshafts and rollers produced with different manufacturing histories. The evaluation utilises standard roughness parameters as well as rough contact parameters. The surfaces measurements are made by a non-contact light interferometer and a set of 3D roughness parameters is evaluated for each measure. The Greenwood- Williamson contact model has been developed and also applied to the measurements in order to collect characteristics of the microscopic pressures. The results of the study show the significant effect of topography variations on the tribological behaviour of the cam roller contact and rank the different manufacturing processes according to functional characterization. The verification of the ranking using experiments is the continuity of this study.