Equilibrium Saturation in Binder Jetting Additive Manufacturing Processes: Theoretical Model vs Experimental Observations

In Binder Jetting 3D Printing process, a feature is fabricated by depositing binder in the selective regions layer by layer until the geometry is completed. One of the main factors which influences the accuracy and strength of the green parts in this process is the spreading (i.e. lateral migration) and penetration (vertical migration) of the binder in powder bed, which is in turn determined by the capillary equilibrium between the saturated regions and the unsaturated powder. In the present study, a previously developed model for binder migration was applied to 420 stainless steel in order to evaluate the equilibrium saturation levels. Characterizations such as contact angle, specific surface area, succession pressure and capillary pressure were carried out in order to determine the theoretical equilibrium saturation amount. Furthermore, 10 single lines with dimensions of 46μm in diameter and 3mm in length were printed out and analyzed for empirical saturation level. The results of the theoretical model and experimental work were compared and discussed in details to validate its applicability in binder jetting process development.