Influence of silica sand particle size on sand-spreading effect and mechanical properties in binder jetting 3D printing

The silica sand particle size plays a crucial role in enhancing the sand-spreading effect and mechanical properties of sand mold via binder jetting 3D printing. Most prior work couples sand particle size with numerous process variables, making it difficult to isolate and elucidate the intrinsic mechanism of particle size alone. To overcome this limitation, a mathematical model describing inter-particle interactions based on the discrete element method was developed in this study. The particle flow code was employed to investigate how six silica sand particle sizes (0.12 mm, 0.14 mm, 0.16 mm, 0.18 mm, 0.20 mm, and 0.22 mm) affect the sand-spreading effect and mechanical properties of printed specimens, with the aim of quantitatively revealing the mesoscale governing relationships between silica sand size and particle packing, contact force transmission, as well as the specimen’s strengths. Concurrently, “8”-shaped and long-bar specimens were printed using the EXONE S-MAX system to measure their tensile strength and flexural strength. The experimental results demonstrate that as silica sand particle size increases, the porosity decreases initially and then increases, whereas the contact force magnitude, tensile strength, and flexural strength all exhibit an inverse trend of increase initially and then decrease. The optimal sand-spreading effect and mechanical properties are achieved at a silica sand particle size of 0.18 mm. Specifically, the simulated and experimental porosities are 4.24% and 4.48% respectively, corresponding to a relative error of 5.4%. The simulated contact force reaches its maximum value of 7.27 kN, while the experimental tensile strength reaches its maximum value of 2.21 MPa. Both exhibit similar variation trends with silica sand particle size. The simulated and experimentally measured flexural strength are 2.93 MPa and 2.84 MPa, respectively, with a relative error of 3.1%. The simulation results are in good agreement with the experimental ones, which provides theoretical support and practical guidance for parameter optimization of binder jet sand printing.