Development of New Sand Casting Mold Composition for Binder Jetting 3D Printing Process Based on Inorganic Binder by Adding Dimensional Accuracy Modifiers: A Comprehensive Analysis of DOE Parameters

This study focuses on optimizing sand mold compositions for binder jetting 3D printing (BJ3DP) using an inorganic binder system tailored for casting applications. Sodium silicate was used as the main binder, with metakaolin, magnesium oxide (MgO), rice starch, and methylcellulose incorporated as modifiers to improve dimensional accuracy, mechanical strength, and thermal resistance. A two-step design of experiments was employed: an initial fractional factorial design for screening, followed by a central composite design (CCD) using response surface methodology (RSM) for optimization. Dimensional accuracy was characterized through water spreading ratio (WSR), which showed a strong correlation with dimensional error. The optimal formulation—2.42% sodium silicate, 7.56% metakaolin, 1.52% MgO, and 2.94% methylcellulose—yielded high flexural strength, improved dimensional precision, and enhanced refractoriness, with a desirability index of 0.958. Experimental casting of aluminum parts validated the mold performance, confirming adequate strength during pouring and acceptable collapsibility post-solidification. These results demonstrate the feasibility of tailoring binder systems for high-precision, thermally stable sand molds in additive manufacturing-based casting.