Geometrical Issues in Design for Binder Jetting - The Effect of Anisotropic Dimensional Change on Sintering

Recent research has been focused on the binder jetting (BJ) additive manufacturing technique due to the high potential possibilities in industrial applications. The actual limitation of BJ process can be attributed to the difficult control of the product quality. In fact, a high dimensional variation occurs on sintering, which can detrimentally affect dimensional and geometrical precision, when not properly considered in the design step.This paper aims at investigating the influence of sintering on the dimensional change of through holes, with different diameter size and different axis orientation with respect to the building direction. Samples were measured in the green and sintered state by means of a coordinate measuring machine in order to calculate the diameter shrinkage. The empirical data were successfully compared with the prevision of an analytical model demonstrating that diameter shrinkage is influenced by: the anisotropic dimensional change, the axis orientation and the position of the two diametral opposite points used to identify the diameter. A deep analysis of the results showed a non-negligible effect of the gravity-induced load and of the inhomogeneous shrinkage on sample geometry. This study highlighted that the analytical model may serve as a basis in the design step for improving the dimensional quality of BJ product.