Geometry Size Effect on Bending Angle and Surface Morphology in Laser Bending

Laser bending, as a mold-free and highly adaptable manufacturing approach, is a promising technique for fabricating microscale components with complex geometries in applications such as microfluidic devices, thermal management systems, and precision engineering, among others. However, the size effect significantly impacts processing precision and forming quality in microscale laser bending, necessitating further investigation to enable reliable micro-manufacturing. The effects of reduced workpiece dimensions and spot size on bending angle and forming quality in laser bending are numerically and experimentally investigated in this study. A 1.5 kW continuous galvanometer laser was used, with spot diameters modified by adjusting the focus position. The effects of spot diameter (expressed as d/h ratios), and sheet thickness (0.20–0.65 mm) on the forming angle and morphological characteristics were systematically examined via single-pass scanning. It was found that the bending angle initially increases but then decreases with the reduction of d/h ratio, accompanied by a "bulging" phenomenon in the bending zone when the decreasing trend is observed. The bulging morphology, quantified by the bulge coefficient ( ξ ), intensifies with decreasing sheet thickness and d/h ratio, which is driven by thermal softening and localized melting. Additionally, edge effects, characterized by relative bending angle variation ( RBAV ) and concave depth of longitudinal distortion ( CDLD ), become more prominent with scaling. To further explore the impact of workpiece and process dimensions, a similarity analysis was performed to investigate the forming characteristics with varying similarity ratios. Similarity analysis further revealed that the geometric similarity ratio ( λ ) is negatively correlated with the bending angle, and the reduction of the similarity ratio enhances the surface bulging. This phenomenon confirms that the geometry size effect exists in the heat transfer. These findings provide critical insights into size effects in laser bending, offering guidance for optimizing micro-forming processes and improving precision in microscale applications.