Process mechanisms for precision control in grayscale printing of additively manufactured sand molds

In purpose of solving the problem of precision deviation caused by droplet penetration in porous media during binder-jet printing of sand molds, the influence of process parameters such as sand mold printing grayscale and printing layer thickness on the performance and forming accuracy of 3D printed sand molds was systematically studied, and the causes of variations in tensile strength and Z-direction dimensional deviation were discussed in this study. The results show that the forming deviation in 3D printing sand molds is jointly affected by printing grayscale and printing layer thickness. When the printing layer thickness is the same, as the printing grayscale increases, the penetration distance of the binder increases, and the forming deviation also increases. When the printing grayscale is the same, as the layer thickness decreases, the forming deviation decreases. Under an optimized parameter setting with a layer thickness of 0.5 mm, the grayscale level of the near-surface layers reduces from 7 to 3. This leads to a 59% reduction in Z-direction dimensional deviation compared to using a grayscale level of 7 across all layers. This research result can provide a technical reference for high-precision sand mold printing and near-net forming of castings.