Abstract
The overhang down-skin surface exhibits distinct behaviors compared to the regular up-skin surface in the powder bed fusion process. Evidence suggests that weak support could be the primary cause of these differences. Previous studies by the authors have indicated that the unique features on the overhang down-skin surface may result from a series of abnormal melting conditions. This paper measures the dross depth of overhang down-skin surface using registered micro-x-ray computed tomography (XCT) data. In addition, it extracts features of the melt pool related to the overhang from overhang 1,000,000 in-situ melt pool images. Four overhang parts with identical geometry and process parameters were fabricated using a powder bed fusion testbed in this study. The results demonstrate that the behavior of the overhang down-skin surface is repeatable across all four parts. The depth of dross is influenced by geometric factors such as the overhang angle and position. The study also reveals that the weak support provided to overhang surface can affect melting in multiple layers, including both the current and future layers. Additionally, this study finds the dross depth and top-surface melt pool size do not have significant statistical correlations. However, a preliminary finding suggests users may identify the extremely large overhang dross formation by monitoring melt pool features in multiple layers above the overhang.
