Error and limit determination for dimensional measurements of thin-walled structures with industrial computed tomography

Due to the high-accuracy requirement of dimensional measurements for thin-walled structures of additive manufacturing products, the grayscale distribution of the industrial CT image and the location of the structural boundaries in the image space were derived. In addition, the validity of the half-height-width method and the maximum gradient method was compared and analyzed, and the limit of the dimensional measurement based on CT imaging was calculated. The thin-walled structures with different thicknesses were calibrated, and measured by industrial CT scanning and imaging experiment. The results show that the half-height-width method generates a smaller error compared with the maximum gradient method, when the thickness of the thin-walled structures is larger than the measurement limit of the CT system. Finally, the measurement limit can be obtained by numerical simulations based on the edge spread function with experimental measurements.