Control of polishing processes by measuring surface roughness according to ISO 25178 / ISO 4288

Correlation between grain size and standard roughness parameters using the Surface Roughness Analyzer – SRA

In addition to dimensions and angles, technical drawings also specify the roughness of workpiece surfaces. This property is decisive for mechanical properties such as friction or flow resistance, but also for chemo-physical characteristics such as susceptibility to corrosion, wettability, or adhesion. The ISO 4288 standard and in particular the ISO 25178 standard propose various test methods for roughness, one of the most important of which is optical, three-dimensional roughness analysis using confocal microscopy.


For this application report, a machine polishing process was simulated using finest grain polishing papers. The aim is to show how the Surface Roughness Analyzer – SRA, which is based on confocal microscopy, can be used to determine roughness parameters according to standard and correlate them with the grit size. In practice, such correlations can be used to check and optimize polishing processes and other surface treatment steps with regard to the roughness specifications.

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