We as ISM3D organize Inter Laboratory Comparisons.
Such comparisons help to prove compliance with the rules of ISO 17025 and the accreditation bodies like DAKKS and ENAC and UKAS.
They are the final proof that one is really capable of calibrations or verifications with the claimed uncertainty.
An example for such a comparison carried out by ISM3D is the one with a ball tetrahedron of Trapet Precision. Please see report below. To download the full final report, please click on the EXCEL symbol on the right top corner of this page and look for the corresponding pdf-file 150224-LC-ENAC-ISM3D-2015 Final 10.3.2016.pdf.
An example of a comparison just initiated is the cylinder square comparison. See below on the right. As well, please download these instructions by clicking on the EXCEL symbol at the upper right corner of this page and then looking for the PDF-file 2018-02-20 Comparison Cilinder Procedure.pdf.
Ball Tetrahedron for intercomparisons with covers of the balls. These covers force the participant to use offset styli ... which makes the test "more interesting" (it´s harder to achieve small errors)
Cylinder square as it is made available for a just initiated inter-laboratory comparison.
Please note that cylinder squares allow for a large number of measurands to be verified, as squareness, parallelity, roundness, length, diameter, cylindricity, straightness, coaxiality, flatness, run out. All this with a very small uncertainty as such cylinders can be made very precise.
The problem is that these cylinders must be calibrated somewhere with high accuracy ... and of course the capability of the (accredited) calibration laboratories for cylinders and any other precise master parts must be assessed. This is what the inter-laboratory comparison is about.
We believe there is nothing better for proficiency testing of laboratories doing 3D calibrations and verifications when form errors and are involved. The tetrahedron (left side) allows for extremely quick machine stability checking ... however the validation of a lrger number of "real" measurement features other than mere distances can be done with this cylinder square.