Room Temperature Deflection Characteristics of Furan Self-Hardening Molds Fabricated Using Additive Manufacturing

The furan no-bake process is widely used because of its applicability to a variety of casting materials. In recent years, it has been applied to additive manufacturing systems. The furan AM process has advantages in the production of complex or long thin cores. Those cores deformed more due to their own weight than in the conventional furan no-bake process. The objective of this study is to determine the deflection characteristics of the mold at room temperature under the application of equally distributed loads. The transverse strength and the deflection of molds were measured under various stress conditions, curing time and humidity conditions. The deflection of molds increases as stress increases or curing time decreases. On the other hand, there is no correlation between transverse strength and deflection. It is suggested that the progressive curing leads to an increase in the degree of polymerization, increase in resin viscosity, and increase in deformation resistance. The deflection characteristics of the mold at ambient temperature are similar to the creep behavior of chemically cross-linked polymers, and it is influenced by the viscoelastic properties of furan resins. Under high humidity, extremely large deflections of molds are observed, which is due to the softening of the furan resin as it absorbs moisture.