Investigation on shape deviation of horizontal interior circular channels fabricated by laser powder bed fusion

Abstract

The fabrication of horizontal interior circular channels poses some unique challenges to the laser powder bed fusion (L-PBF) process. The engineering challenge is to be able to print horizontal interior channels using L-PBF without using support structures, while the scientific challenge is to predict the shape deviation in the horizontal channel. This paper studies the geometric fidelity (roundness and shape deviation) of L-PBF printed horizontal interior circular channels (diameters 1− 3 mm) by developing experiment-based regression models and a preliminary computational fluid dynamics (CFD) simulation model. The roundness error is found to be affected by the shape/size of the melt pool, thermal stresses, beam offset, and the slicing algorithm. It is recommended that to decrease the roundness error, in addition to choosing a proper beam offset, the width/depth of the melt pool should be minimized by minimizing the volumetric energy density (smaller laser power or higher scanning speed). Shape deviation in overhanging structures is determined by the thermo-mechanical driven molten flow in the melt pool. Hanging structures with irregular profiles (dross) are formed due to the sinking of the melt pool on an unconsolidated powder bed under the effect of gravity, surface tension, and poor thermal conductivity. (Partially) unmelted powder randomly adheres to the edges of the melt pool enlarging the hanging structure and roughening the profile. Small laser power or large scanning speed benefits reducing the roundness error and hang-diameter ratio. 0 • or 45 • rotational linear scanning strategy can be selected for minimizing the roundness error or the hang-diameter ratio, respectively.

Additive Manufacturing of Intertwined Electrode Pairs ‐ Guided Mass Transport with Gyroids

“…[21] We design all electrodes to exhibit a mainly porous structure, increasing the specific surface area beyond the already considerably rough surface which is a result of the fabrication process from metal powder. [29,30] The porosity, which is especially pronounced on overhanging structures, [31,32] is embraced rather than avoided, as it is deemed beneficial to the creation of high surface areas.…”

Design and Flow Analysis of Special-Shaped Cross-Section Flow Channel Based on Selective Laser Melting

“…Duan Shengqin et al [21] has optimized the surface quality of the overhanging circular hole by changing the laser power, scanning line angle and number of contour scans. Shaochuan Feng et al [22] related roundness and shape deviation of circular channels to melt pool morphology, thermal stress, spot compensation and scanning strategy to reduce shape deviation by changing spot compensation, reducing energy density, and selecting scanning strategy with 0° or 45° rotation. Amar M. Kamat et al [16] developed a model for predicting deviations in three different cross-sectional shapes (circular, elliptical, and diamond) that can compensate for shape deviations at the design stage.…”

Surface Roughness and Design for Additive Manufacturing: A Design Artefact Investigation

“…These unsupported areas, such as the internal roofs of enclosed structures, lack sufficient heat conduction pathways during the build process. Hence the cooling of material is slower, and the molten material flows through to the powder bed beneath, causing a fusion of melted and un-melted powder on the exposed surface (dross) (Feng et al, 2020). Intrinsically linking dross formation and rough surfaces to design choices such as inclination angle, curvature, and surface thickness (Jones et al, 2021).…”