Dimensional accuracy and surface roughness of thin-wall geometries in laser powder bed fusion of 316L stainless steel

Abstract

Thin-wall geometries produced by laser powder bed fusion combine high manufacturing efficiency, design flexibility, and cost-effectiveness for specialized applications. In such features, surface quality directly impacts dimensional accuracy and functional performance. This study investigates the effects of laser power, scan path, build orientation, and nominal gap distance on the top- and vertical-surface roughness, surface features, and dimensional error (DE) of 316L stainless steel thin walls. Optical microscopy was employed to characterize melt pool morphology and surface characteristics. Increasing laser power enlarges melt pools, promotes lateral migration, and induces dross formation on vertical surfaces, raising roughness and DE. Incorporating a contour scan with an inward offset reduces the scanned area, limits melt pool migration, and improves dimensional accuracy. Print orientation has a negligible influence on DE under the tested conditions, while small gaps may close entirely at high power due to large melt pools and migration. Compared to cubes fabricated with identical parameters, thin walls exhibit rougher top surfaces at high power, attributed to reduced track overlap, limited wetting from previous layers, and powder redistribution near vertical edges, whereas vertical-surface behavior remains similar. These findings provide practical guidelines for optimizing dimensional accuracy and surface quality in thin walls through coordinated control of process parameters and geometry.

Keywords

Additive manufacturing / Thin-wall structures / Surface roughness / Dimensional accuracy / Melt pool migration

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