Dimensional and geometrical precision of parts produced by binder jetting process as affected by the anisotropic shrinkage on sintering

Dimensional and geometrical precision of parts produced by binder jetting is a crucial issue to be considered aiming at promoting the transition to industrial production. The influence of both the printing and the sintering processes has to be evaluated, and the high shrinkage has to be considered. The task is further complicated by the anisotropy of dimensional change on sintering. The aim of this work is to investigate the dimensional and geometrical precision of cylindrical holes, as affected by the anisotropy of dimensional change on sintering after binder jetting. AISI 316 L powder was used to produce five different geometries, characterized by four holes with different orientation with respect to the printing direction. The geometrical features were measured both in the green and in the sintered state with a coordinate measuring machine, and the dimensional changes, as well as the geometrical variations, were calculated. According to the author's previous experience, a theoretical model has been defined, which aims at predicting the geometry of the holes as derived by the anisotropic dimensional change on sintering. The expected dimensional change of hole diameters, the variation of cylindricity, and the variation of the axis inclination were calculated by the model and compared to those derived from measurement. Good agreement between predicted and measured results has been observed, providing that the influence of printing process parameters is considered.