Advanced Surface Analysis to Identify Media-Workpiece Contact Modes in a Vibratory Finishing Processes

This paper outlines a robust data processing approach capable of isolating individual process related features such as grinding marks, pits, and scratches from an areal surface measurement of a ground sample that underwent a modified vibratory finishing processing step. The approach combines conventional surface segmentation and feature isolation approaches, with polar plots developed by this research group. Motivation for the work assumes that the mode of media-workpiece interaction occurring during the process, i.e., impact or sliding, can be inferred from the topological features present on the workpiece surface post finishing. Sliding contact is expected to induce scratches, while impact will create local pits. To evaluate the proposed surface analysis approach, two aluminium 6061 samples that were used in previous vibratory finishing tests were re-analysed. In additional to the coherent scanning interferometric areal surface measurements, high speed imaging, particle imaging velocimetry, and computational fluid dynamics models of the media flow around the workpiece is available to verify the media-workpiece interaction modes suggested by the surface analysis approach. By verifying the effectiveness of the approach via the previous imaging and modelling efforts, it becomes possible to understand the nature of the workpiece media-interaction in regions of the vibratory finishing bowl that are not accessible by imaging techniques, i.e., near the bottom of the bowl. The approach can successfully isolate media related pit marks and scratches while also providing information regarding the direction of media motion across the workpiece surface and insights on the nature of the local media pressure fields conditions.