Systematic selection and evaluation of relevant surface roughness parameters for the characterisation of the innovative RPM-Synchronous Grinding process

Abstract

The key to high performances and long lifetimes of machine components in lubricated contacts is often the surface topography. Its characteristics can be derived in numerous ways from 3D topography measurements, but these procedures do not follow any existing standards, resulting in limited comparability. In this work, we present a new, universally applicable workflow to reveal the most significant roughness parameters for a comprehensive description of differences in surface topographies. This workflow, based on principal component analysis (PCA), offers a standardization of parameter selection. It is applied to RPM-Synchronous Grinding (RSG), a novel grinding process that enables the production of non-circular geometries without an oscillating movement. To increase trust in this new technique, knowledge on how the process parameters affect the surface topography is required. Numerous statistical roughness parameters were derived from 3D confocal light microscopy as well as 2D tactile measurements on each ground workpiece. We apply the proposed workflow and find that, for the selected RSG parameter variations, Rq is the most relevant roughness parameter to capture changes in the surface topography. The 100 % fused white aluminum oxide grinding wheel, opposite grinding direction, and a low specific material removal rate result in the smoothest surfaces. A high degree of usage of the grinding wheel leads to higher Rq values, but there is a trend to reach a plateau value. The RSG machined workpieces are compared to conventionally ground and shortly run camshafts. The camshafts have Rq values in the range of the rougher RSG machined surfaces, but there are significant differences in the parameters Ssk, Sku, Sv and Vvv. Provided the number of workpieces is high enough for statstical analysis, we propose to apply our workflow for the selection of the most relevant roughness parameters to describe the differences between surfaces obtained by different machining parameters and processes.