A novel approach for the quantitative characterization of shrink lines in the powder bed fusion of metals using a laser beam

The powder bed fusion of metals using a laser beam (PBF-LB/M) enables the manufacturing of complex geometric designs with no part-specific tooling. As a result of the high energy input, the temperature gradients lead to a warpage of the part. Particularly at the structural transitions, thermally induced deformations form a shrink line on the outer surface of the geometry during PBF-LB/M. These shrink lines present a small notch, which reduces the dimensional accuracy and the part lifetime. However, the quantitative analysis of the shrink lines and their influencing factors has not been investigated yet. To specify the geometric characteristics of the shrink lines, a measurement approach is presented to enable their reliable and precise evaluation. A suitable test specimen was identified and varied within its geometrical dimensions. The results demonstrate the reproducible quantification of the shrink lines and their geometric characteristics. A significant dependence of the shrink lines on the geometry of the specimens is observed.