Comparison of different voxel size calibration strategies

Abstract

Coordinate measuring machines (CMM) are traditionally used in industry for verifying geometric dimensions and tolerances of parts. In the last decade X-ray computed tomography (CT) is being increasingly used in industry for dimensional analysis purposes as well. Tactile CMM is based on point-to-point collection of measurement data, while CT scans entire workpiece and generates a volumetric point cloud of measurement data. The influence of different approaches in gathering of data when using CMM and CT on calculation of voxel size is experimentally tested and discussed in this work and compared with other standard voxel size calibration options like use of reference standards and calibration of magnification axis. Several typical industrial workpieces are used to demonstrate the differences that arise because of different voxel size calibration strategies.

Charting the course towards dimensional measurement traceability by x-ray computed tomography

“…A voxel rescaling factor is determined from a linear fit of the CT measurements to their calibrated values. Katić et al [77] compare the use of calibrated features on the test object to using a separate calibrated reference object to calibrate the voxel size. While the experimental results do not provide a clear delineation between the two approaches, Katić et al provide a meaningful discussion on how shape deviations in the reference features used to calibrate the voxel size will render one approach more suitable than the other.…”