High precision roundness measurement by error separation techniques

Project Description

The comparison has been proposed and is organised by CEM (ES) as a continuation of the EURAMET comparison L-S23.(2013). The aim is to solve difficulties found by some participants in the previous comparison due to the lack of metrological quality of the circulating sphere. CEM, after locating high quality standard spheres, proposes this new comparison in order to know the real capabilities of measuring roundness in spherical standards by applying error separation techniques to seek the lowest uncertainty. The comparison is ready to start after consultation with some participants, most of whom were also involved in the previous comparison.

Final Report 2022-02-07

The comparison has been completed and results are available in the KCDB..

Comparison piloted by CEM (ES), continuation of previous comparison EURAMET.L-S23. Artefacts selected were 2 alumina spheres of 20 mm and 25 mm. Five National Metrology Institutes from EURAMET participated in this comparison, which lasted nine months, from March 2020 to November 2020.
The measuring was the roundness on the equator of the spheres. Peak-to-valley roundness deviation (RONt) had to be evaluated with reference to the least squares reference circle (LSCI) and, if possible, to the minimum zone reference circles (MZCI), in accordance with the ISO/TS 12181-1:2011.
Each laboratory had to use an error separation technique to remove the contribution of the spindle error. In case of using a multistep technique it was advisable to inform on the number of steps used.

All participants have successfully demonstrated the validity of the claimed measurement capability. Three of them submitted their approved CMCs and two others smaller values which were shown to be valid when compared to the reference value. One participant did not use error separation technique, showing, as expected, a higher uncertainty with respect to the rest of participants but according to its declared CMC.

Progress Report 2020-10-21

Artefacts selected were 2 ceramic spheres of 20 mm and 25 mm. The comparison started in February 2020 as scheduled. On the date of this progress report, the results from all participants, VSL, DTI, INRIM and LNE have been already received. So, only final measurements of CEM are needed to close the circulation. The finalisation of the comparison is expected by December 2020.