Dimensional measurements of additive manufacturing parts: A comparison of X-ray computed tomography and coordinate-measuring system using physical and simulation approaches

The purpose of this study is to assess the effectiveness of X-ray Computed Tomography (XCT) in measuring dimensions of additively manufactured (AM) parts, and compare it to a well-established tactile coordinate-measuring system (CMS). The study investigates three factors: XCT beam hardening, XCT voxel size scale error, and CMS mechanical filtering effect. The performance of XCT and CMS in measuring a half-smooth and half-rough AM hollow cylinder is compared. To complement physical measurements, simulation methods are used to investigate the individual impacts of XCT beam hardening and CMS mechanical filtering effect. The physical experimental results show that the elimination of XCT beam hardening aids in obtaining accurate internal dimensions but deteriorates external dimensions. XCT voxel size scale error can be compensated by either the two-sphere calibration or the CMS normalization method. However, it is essential to ensure that these methods are based on an accurate reconstruction volume. The physical measurement results suggest that the deviation between XCT and CMS measurements of the rough cylinder part is mainly due to the mechanical filter effect of CMS, which is further confirmed by simulation measurements.