Effect of Process Co-Factors on Repeatable Process Capability for Subscale Feature Dimensions in PBF-LB/M Additive Manufacturing of TI6Al4V

This article addresses the lack of repeatability and reproducibility that has inhibited the widespread adoption of Laser Powder Bed Fusion Additive Manufacturing (PBF-LB/M) for service-critical part fabrication in production. A rigorous analysis of critical dimensional variations at a statistically significant scale is essential to understand the influence of process co-factors in PBF-LB/M, serving as a vital step toward process control. Structured white-light profilometry provides an effective balance of capability and features for performing such analysis, including advanced focus variation-based feature extraction. In this work, two types of samples were fabricated, each having either thin gaps or thin walls of varying widths ranging from 200 to 1000 µm. Samples containing these features were designed with and without a constraining base geometry and built along different orientations across various locations on the build plate in two layer thicknesses: 30 µm and 60 µm. Co-factors such as base geometry, specimen orientation, layer thickness, and location on the build plate were investigated for their impact on measurement variations in the as-built condition. The achievable resolution and repeatability was found to be 500 μm, and thus did not conform to the machine manufacturer’s stated minimum of 150 μm. The presence of a base geometry effectively reduced the variations preferentially for features larger than this limit. Features smaller than 500 µm exhibited a variation of approximately 1.5–3 times the D50 size of the powder feedstock, regardless of the co-factors. The tightest control over the variations was observed to occur at the center of the build plate. This study aims to quantify the combined effect of multiple process co-factors on the repeatable dimensional process capability of sub-millimeter PBF-LB/M features in Ti6Al4V.