Process optimization strategy for metallic lattice structures fabricated by laser powder bed fusion: a method integrating orthogonal experimental design and the Gibson-Ashby model

Abstract Additive manufacturing, such as Laser Powder Bed Fusion (LPBF), has made it possible to precisely fabricate complex metallic lattice structures. However, the lower surfaces of metallic lattices exhibit numerous fabrication defects, such as coarse sub-grains, irregular closed pores, and surface protrusions, which result in a low cost-performance ratio while increasing the actual relative density. In this study, an orthogonal experimental design was used to investigate the effects of process parameters on the actual relative density and mechanical properties of 316L diamond lattice structures. The results show that the leakage region of the metal solution results in a larger strut size and a higher actual relative density than the design values. Consequently, for the 316L diamond lattice, a lower actual relative density often brings the yield and compressive strengths close to the upper theoretical Gibson-Ashby curve, whereas a higher actual relative density results in strengths below that curve. By comparing the experimental data with the theoretical Gibson-Ashby curves, the optimized process parameters for fabricating 316L diamond lattices were determined to be a laser power of 260 W, a scanning speed of 1400 mm/s, and a hatch spacing of 0.09 mm. Finally, the cell size was enlarged to further validate the process optimization strategy, and the same optimal process parameters were obtained, thereby confirming, to some extent, the feasibility of the process optimization strategy.