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In this work, we present a fully atomistic approach to modeling a finishing process with the goal to shed light on aspects of work piece development on the microscopic scale, which are difficult or even impossible to observe in experiments, but highly relevant for the resulting material behavior. In a large-scale simulative parametric study, we varied four of the most relevant grinding parameters: The work piece material, the abrasive shape, the temperature, and the infeed depth. In order to validate our model, we compared the normalized surface roughness, the power spectral densities, the steady-state contact stresses, and the microstructure with proportionally scaled macroscopic experimental results. Although the grain sizes vary by a factor of more than 1,000 between experiment and simulation, the characteristic process parameters were reasonably reproduced, to some extent even allowing predictions of surface quality degradation due to tool wear. Using the experimentally validated model, we studied time-resolved stress profiles within the ferrite/steel work piece as well as maps of the microstructural changes occurring in the near-surface regions. We found that blunt abrasives combined with elevated temperatures have the greatest and most complex impact on near-surface microstructure and stresses, as multiple processes are in mutual competition here.

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The RPM-Synchronous Grinding process offers new possibilities to generate defined macro- and micro-geometries on workpieces. With present technology, various macroscopic non-circular geometries must be grinded subsequently in an oscillating process where the X-axis is coupled with the rotary workpiece-spindle axis. Such workpieces can be machined in an ordinary plunge grinding process by implementing the approach of RPM-Synchronous Non-Circular Grinding. Therefore, the workpiece and the grinding wheel rotational rates are in a fixed ratio. A non-circular grinding wheel is used to transfer its geometry onto the workpiece. The authors use a unique machine tool for basic research and control concept development for RPM-Synchronous Grinding (RSG). The machine was especially designed for this RSG technology. Highest revolution rates on the workpiece spindle are mandatory for its success. The grinding approach is performed in a two-step process. For roughing, a highly porous vitrified bonded grinding wheel with medium grain size is used. It ensures high specific material removal rates for producing the non-circular geometry on the workpiece efficiently. A control algorithm adapts this process step, which uses acquired data from a piezoelectric three-component force sensor fixed at the tailstock-side of the grinding machine. For finishing, a grinding wheel with fine grain size is suited. This process step is tuned by a digital process adaption strategy. Roughing and finishing are performed consecutively among the same clamping of the workpiece with two locally separated grinding spindles. With the presented control and adaption concepts for RPM-Synchronous Grinding, a significant increase in surface quality on the workpiece is attained. The minimization of grinding wheel wear results concurrently. Especially the automotive industry shows big interest in RPM-Synchronous Non-Circular Grinding. This emerging trend in finishing machining opens up various fields of application.

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.