<p>In this study, the solidification microstructures of ultra-thin cellular structures of Al-11Si alloy were investigated. For this purpose, an indirect additive manufacturing method combined with suction casting was employed. Initially, the polymer models with a cubic geometry and wall thicknesses of 0.5, 0.75, and 1.0 mm were fabricated by SLA (stereolithography) 3D printer. Following plaster molding, the melting process was carried out by the suction casting method under an argon atmosphere. Subsequently, the apparent density, casting defects, microstructure, and microhardness of the samples were evaluated. The results showed that the lattice structure with cell wall thicknesses as low as 0.5 mm can be successfully manufactured using suction casting in plaster molds. The microstructure of the samples consisted of primary alpha-aluminum dendrites and eutectic silicon flakes. As the cell wall thickness increases, the alpha-aluminum dendrites became larger, while the eutectic silicon flakes became finer and shorter. The apparent density of the samples decreased from 1.287 to 0.411 gr/cm³ as the cell wall thickness decreased from 1.0 to 0.5 mm. The main casting defects, including hot tearing and external inclusions from the mold, increased with decreasing cell wall thickness. Furthermore, the samples' microhardness decreased with increasing cell wall thickness due to the refinement of the eutectic silicon flakes.</p>