Influence of powder characteristics on shrinkage behavior of 3D-Printed glass structures

The anisotropy of shrinkage that occurs during the sintering of glass needs to be carefully understood for proper fabrication of 3-dimensional (3D) glass structures using a binder-jetting additive manufacturing process. Although the time-dependence of glass sintering is governed by viscous flow, the effect of the powder characteristics and process parameters during printing need to be considered. In this study, the size and morphology of glass powders were varied as material parameters for obtaining optimal powder characteristics. Glasses composed of SiO2-B2O3-ZnO-BaO-Al2O3, with different sizes and morphologies, were used as printing materials. Different powder stacking orientations were considered as additional parameters affecting shrinkage behavior. The anisotropy degree was obtained by measuring the ratio between the axial contraction and the radial contraction of samples sintered for different amounts of time. Both frit and glass bead exhibited anisotropic shrink behavior. However, the spherical glass bead was the closest to isotropic shrinkage and showed an effective shrinkage rate for the formation of a designed 3D glass structure and densification of the microstructure.