Printing-induced particles segregation governs anisotropic shrinkage in binder jet additive manufacturing

Abstract Anisotropic shrinkage during sintering is limiting the widespread adoption of Binder Jet Additive Manufacturing (BJAM) by undermining its ability to produce complex, near-net-shape parts. Prior studies often attribute sintering anisotropy in BJAM-printed samples to factors such as gravity or heterogeneities in packing density. While emerging evidence indicates that powder segregation during printing induces particle-size heterogeneities, its influence on the anisotropic sintering of BJAM-printed samples has not been explored. This study investigates the relative effect of density and particle size heterogeneities on anisotropic sintering by developing a digital twin model to simulate the BJAM process. The model captures the dynamics of particles during the powder spreading process, including particle segregation, using the Discrete Element Method (DEM), enabling spatially resolved representations of packing density and particle-size heterogeneities. It also simulates the sintering response of the samples using the continuum theory of sintering (CTS) implemented in finite element (FE) code. Capability of the developed model is verified and validated using experimentally measured results for BJAM-printed samples from literature. It is revealed that particle-size heterogeneities, caused by powder segregation during printing, govern anisotropic shrinkage during sintering of binder-jet-printed samples. Furthermore, it is also shown that mismatches in lateral shrinkage rates, arising from particle size and density heterogeneities, can lead to surface roughness. The work highlights the need for optimizing feedstock particle size distributions and powder spreading parameters to control anisotropic shrinkage in BJAM process. Graphical abstract