Results of the international comparison of ball plate measurements in CIRP and WECC

Abstract A comparison was conducted for the calibration of commercially available ball plates. Twenty six metrology laboratories from fifteen countries participated with a total of thirty eight individual measurements. The method of measurement was strictly prescribed and the results were evaluated by the PTB as the reference laboratory in comparison to the reference values. The measurements showed a high degree of conformity of about 2·10−6 in over 60% of all cases. In 30% evident problems which can easily be overcome were the reasons for less good results. The ball plates showed sufficient dimensional stability over time of about 1·10−6 per year (in the worst case). Findings resulting from the intercomparison suggest ways to improve the stability of ball plates by better design details.