Final report on APMP.L-K8: International comparison of surface roughness

Abstract

Surface roughness calibration services of 16 countries from four metrology regions are compared through measurements of roughness and step height standards. The artefacts circulated include three steps of nominal depths 0.4 µm, 2.4 µm and 10 µm, whereas the roughness sections of both type C and type D profiles have nominal Ra values of 0.2 µm, 0.95 µm, 1.5 µm and 3.1 µm. Two soft-gauges were also circulated for comparison of software independent of hardware. For the steps, parameter d is reported, while for the type C and type D standards and soft-gauges, 14 different roughness parameters are reported between them. Concluding measurements from the pilot in general show good standard stability; however, for some parameters on the artefacts of larger roughness, stability may be considered less certain and this may be an issue in additional outliers in results from the last few laboratories in the schedule. For each parameter, a key comparison reference value (KCRV) is determined using a weighted mean with outliers excluded based on the Birge ratio method until all accepted values form a statistically consistent population. For the five artefacts, out of 35 separate parameters, only ten have good agreement of all submitted results. Where some parameters had to be excluded from the KCRV, some laboratories had consistent problems with particular types of parameter over the different artefacts, while for other laboratories the types of parameters excluded seemed to be random. Comparison of soft-gauge results and artefact results has proven to be inconclusive.Main text.To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/.The final report has been peer-reviewed and approved for publication by the CCL, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).