Influence of resolution on the X-ray CT-based measurements of metallic AM lattice structures

Additive manufactured (AM) lattice structures have become very prominent in recent times especially in air and spacecraft industry for their lower weight and specific mechanical properties. Their stiffness and strength can be controlled by their geometrical properties, such as the shape and dimensions of the unit cell. Geometrical and dimensional accuracy of the AM lattices is therefore one of the most important requirements to meet the desired functionality as there could be significant deviations in the as-produced part from the designed model; thus, their measurements are of great significance. X-ray computed tomography (CT) has emerged as a promising solution in the field of industrial quality control over the last few years due to its non-destructive approach. However, CT measurement accuracy depends on various parameters (part material, system, operator, environment, data post-processing), among which the resolution or voxel size of the CT data is crucial. In this work, the influence of resolution on the measurement of metallic lattice structure is studied by means of simulations and real CT experiments. The optimized CT acquisition settings are obtained with the help of simulated radiographs and design-of-experiment approach. Three different resolutions are achieved by placing the part at different positions from the X-ray source. The computer-aided design (CAD) model comparison reveals that the majority of surface has a deviation of ± 0.2 mm and the results are slightly affected by the resolution. The wall thickness analysis provides a global observation of the strut and node thicknesses. Individual struts are measured with representative regions of interest (ROIs) considering the manufacturing direction. The measurement results are significantly affected by the resolution (or voxel size) of the CT data. Simulated CT scans with different resolutions have been performed for systematic error estimation in relation to the voxel size.