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3D roughness standard for performance verification of topography instruments for additively-manufactured surface inspection

Jones, C W; Sun, W J; Boulter, H; Brown, S (2022) 3D roughness standard for performance verification of topography instruments for additively-manufactured surface inspection. Measurement Science and Technology, 33 (8). 084003

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The unique complex topography of additively-manufactured surfaces – and the recent rapid evolution of instruments and techniques to measure them – limits trust in inspection data, in direct conflict with the requirements of application areas such as aerospace, where failure of a part can have dire safety consequences. Topography instrument manufacturers and end-users require measurement standards with a controlled reproduction of representative additively-manufactured surfaces to calibrate, performance-verify and intercompare instruments for inspection tasks, thereby improving confidence in measurement.

We report a design of such a surface texture measurement standard, optimised for optical areal topography-measuring instruments and compatible with X-ray computed tomography instruments. Machined from an additively-manufactured blank, the standard’s four sides represent increasing levels of post-processing from the as-deposited surface. Datum features on the measurement standard facilitate direct comparison between instruments and integrated step features support the verification of an instrument’s calibrated Z scale.

We report reference Ra and S-parameter measurements and associated measurement uncertainties for a prototype standard matched to a typical aerospace ScalmalloyTM additive manufacturing process. In doing so, we demonstrate the feasibility of using a large area chromatic confocal microscope to calibrate relatively rough roughness measurement standards. We also briefly discuss ways to decouple the reproducibility of the measuring instrument under test from the inherent variability of a nominally-uniform reference standard deliberately based on as-deposited additively manufactured surfaces.

Item Type: Article
Keywords: dimensional metrology, surface topography, performance verification, additive manufacturing, calibration, roughness standard
Subjects: Engineering Measurements > Dimensional
Divisions: Materials and Mechanical Metrology
Identification number/DOI: 10.1088/1361-6501/ac6397
Last Modified: 02 Oct 2023 13:19
URI: http://eprintspublications.npl.co.uk/id/eprint/9604

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