Measurement systems analysis for beam compensation, scaling factors and geometric dimensioning for a metallic additively manufactured test artifact

Freedom of design is a major tenant of additive manufacturing (AM); however, this necessitates the evaluation of advanced measurement systems for comprehensive part evaluation to ensure production of geometries as intended. This research analyzed contact [Coordinate measuring machine (CMM) and Caliper] and non-contact [Optical and X-ray computed tomography (XCT)] measurement systems on as built and surface finished qualification test artifacts (QTA), from the Global Test Artifact Data Exchange Program, fabricated in Ti-6Al-4 V using a laser powder-based fusion (LPBF) system. The CMM measurements were performed at a certified laboratory, while the other measurements were taken at the W. M. Keck Center for 3D Innovation at UTEP using standard operating procedures for applicable systems. The use of Calipers measurement methods is recommended for general beam compensation and scaling factor adjustments. Measurement differences when calculating beam compensation from the benchmark method (CMM) and (Caliper) was 0.020 mm and the difference between CMM and the Optical method was 0.010 mm, when analyzing the surface finished artifact. Highly accurate methods, such as CMM, are recommended for individual feature adjustments and only when the manufacturing process and post process tolerances capabilities are less than 0.020 mm which in case of LPBF systems is not achievable. For GD&T characteristics, the differences between CMM and XCT measurements were similar (0.050 mm) across the reported zones for tolerances, within a surface roughness range of Sa = 0.004–0.011 mm. This indicates that the contributing factors to measurement variations are not only related to surface roughness but also include the configurations of the measurement systems. These configurations encompass the definition of edges or faces, the location and size of the measured features, and the type of feature being evaluated.