The furan material system in sand binder jetting experiences binder migration, causing problems such as sand adhesion and dimensional variation. This work presents a binder jetting process using a grayscale printhead to precisely control droplet size and binder content. By studying the migration mechanism, the effects on dimensional variation are analyzed, providing insight into transport mechanisms and reaction kinetics. By implementing varying binder concentrations in the surface layer, stair steps are eliminated, resulting in improved casting quality and demonstrating the effectiveness of the approach.