Proceedings of the
9th International Conference of Asian Society for Precision Engineering and Nanotechnology (ASPEN2022)
15 – 18 November 2022, Singapore

Measurement of Additively Manufactured Internal Surface Structure Using an X-ray Computed Tomography

Shihua Wanga and Shengkai Yu

Optical Metrology, National Metrology Centre (NMC) Agency for Science, Technology and Research (A*STAR) 8 CleanTech Loop Unit 01-20, Singapore 637145


The measurement of external surface topography including regular and random rough surface structures fabricated by conventional machining process has been well developed. However, it is impossible for those methods based on the stylus or optical profilometry to conduct measurements of internal structures fabricated by additive manufacturing (AM) process since the related stylus/optical probe cannot access internally hidden areas of interest. Advanced X-ray computed tomography (XCT) offering micro-scale resolution can do it as X-ray can penetrate the materials and then pick up the hidden surface information. In this study, we prepared internal surface structures present in additively manufactured parts and successfully conducted measurements using an advanced high-resolution XCT. To quantitively demonstrate XCT feasibility for measuring internal surface structures, both conventional turned part and AM part assembled to be internal surfaces were measured by the XCT. The XCT 3D surface topography measured shows clear images of the internal structure with 4 flat surface step heights of Type A1 (ISO5436-1) ranging from 30 µm to 250 µm on the internal surface of the turned part and varied areal surface roughness values of Sa (ISO 25178-2) ranging from 4 µm to 20 µm on AM internal surfaces. Corresponding XCT measured results are favorably comparable to those reference values obtained by a traceable laser confocal microscope. It successfully demonstrated that the proposed XCT methodology is non-destructively and quantitively capable of providing micro-scale surface topography data comparable with conventional surface measurement technologies. In addition, the designed parts can be used as testing coupons for verifying the XCT measurement accuracy of the AM fabricated internal structure.

Keywords: Advanced manufacturing and engineering, Additive manufacturing, Step height, Surface roughness, X-ray computed tomography, Laser confocal microscope

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