Evaluation of CT and CMM measurement uncertainty for an additively manufactured AlSi10Mg test artifact

Additively manufactured (AM) components are increasingly utilized in industrial applications due to their ability to produce complex geometries. However, the evaluation of their dimensional accuracy and surface quality remains challenging due to the inherent roughness and geometric complexity of AM surfaces. This study examines a test artifact based on the standard DIN EN ISO/ASTM 52,902, featuring pins, holes, spherical elements, length test specimens, and inclined surfaces to comprehensively assess dimensional accuracy and surface properties. A tactile coordinate measuring machine (CMM) and a computed tomography (CT) system were employed for measurements. The CMM provided tactile reference measurements, while the CT system enabled non-contact volumetric analysis. Comparative measurements using a calibrated PTB reference hole-plate validated systematic deviations between the two techniques, confirming consistent scaling errors and surface-related effects. For the AM artifact, unidirectional distances deviated up to 5 μ m, while bidirectional distances showed a consistent offset of approximately 40 μ m. These discrepancies were associated with the surface roughness of the test specimen and scaling errors. A detailed uncertainty analysis revealed an expanded measurement uncertainty of 41.0\;μ m for bidirectional distances, with the largest contributions from surface roughness. (𝑢 𝑤 = 13.6 μ m) and systematic errors (𝑢 𝑏 = 15 μ m). The results show the limitations of tactile CMMs in detecting features of rough AM surfaces. These findings emphasize the need for a thorough understanding of the measurement uncertainties associated with both methods, particularly considering the surface properties in AM components.