A dimensional assessment of small features and lattice structures manufactured by laser powder bed fusion

Abstract The understanding of dimensional variations produced by laser powder bed fusion is critical in components with small features and with dimensions close to the inherent limits of the process. In this context, two reference geometries were used: (a) straight walls to quantify dimensional relative error for small features and (b) a latticed neck region of a fatigued specimen (cubic and hexagonal cell design, with design strut sizes of 250 µm, 500 µm, and 1000 µm in cell size). Samples were fabricated out of AISI 316L stainless steel powder with different building orientations. The metrology techniques used were the following: focus variation microscopy, optical microscopy and micro-computed tomography. The straight wall characterization shows that built orientation does not influence dimensional relative error for walls with less than 750 µm. Acceptable dimensional relative errors (~ 2% to ~ 15%) are achieved only in walls with 750 µm in width of more. For lattice structures, the fine struts (250 µm) show a significant level of dimensional relative error (~ 5% to ~ 25%). This additive manufacturing process delivers more consistent dimensions for coarse struts (500 µm), with relative errors between ~ 2% and ~ 4%. All metrology techniques showed the same trends in terms of capturing the dimensional variations for fine and coarse struts.