Dimensional XCT comparison campaign on an aluminium object

An x-ray computed tomography (XCT) interlaboratory comparison campaign, involving an aluminium-machined object, whose dimensions (92 × 78 × 63 mm3) are significant for a 225 kV XCT system, was performed for the purpose of investigating the performances of industrial XCT systems for dimensional measurements in terms of accuracy, i.e. precision and trueness, and to evaluate the influence of the measurement protocol (i.e. measurement strategy), of the operator and of the software on the results by comparison to reference measurements. In this campaign, we came to the conclusion that the measurement strategy is predominant, except for distance; that the measurement process is affected by the operator only for cylindricity and coaxiality; that there is no or little influence of the software except for coaxiality and position; and that a volumetric Gaussian filter allows to improve the measurements only for some participants' measurements Furthermore, different behaviours, in terms of precision and trueness, are observed depending on the type of measurands when performed by different operators. The diameter measurements are reproducible with XCT, lower than 30 µm which corresponds to a subvoxelic factor of 2.5 and the trueness is lower than 22 µm. The distance measurement is also reproducible with XCT, 15 µm which corresponds to a subvoxelique factor of 4.9 and the trueness is 8 µm. For these mesurands, their measurements do not depend on the used XCT system. However, the XCT reproducibility for cylindricity, coaxiality and position is worse as well as of the trueness except for the position which has a trueness of 1 µm. The process measurement should be revised regarding cylindricity and coaxiality measurements. Finally, overall, the ability of the participants to perform measurements with XCT, whatever their system, is statistically comparable except for a few measurements.