Influence of Molding Position on Packing Fraction for Sand Mold Fabricated by Binder Jet Additive Manufacturing

Abstract

  The sand packing mechanism of sand molds made by Additive Manufacturing (AM) may change in three dimensions because sand molds are made by repeatedly stacking sand layers. Since the packing fraction of a sand mold made by AM is closely related to its strength, there is a need to understand the packing fraction distribution within the molding area. In this study, the packing fraction of sand molds and uncured sand in the molding area was investigated three-dimensionally in order to improve the strength of sand molds made by AM. The results revealed the following. Sand mold specimens molded directly above the table surface are subjected to load due to the spread and weight of the sand, which increases the packing fraction of the sand molds. Molding the sand mold specimens adjacent to each other in the stacking direction may prevent decrease in the packing fraction of sand molds made at a distance from the molding table. Uncured sand has a higher packing fraction than hardened molds, and the closer the sand mold to the molding table, the higher the packing fraction of the uncured sand. These findings are useful for increasing the strength of sand molds made by AM.