Metal Binder Jetting (MBJ) is a layer-by-layer 3D-printing process consisting in selectively injecting a binder into a powder bed in order to bind metal particles together. After the overall printing of the part and the curing step, a “green” part is obtained.  To achieve the final part, further treatments such as debinding and sintering are required. While extensive work has been conducted on the sintering of different materials, only few studies have tackled the relationship between process parameters, printing mechanisms and green part properties (strength, relative density and dimensional accuracy).

In this work, the focus is placed on the understanding of the binder-powder interaction during printing on a fine SS316L powder, as well as the effect of the related process parameters on the quality of the green parts. The geometry of the representative unit volume infiltrated by a single drop was determined and the competition between spreading and infiltration of the binder was investigated. A model was developed to predict the in-printing penetration depth of picoliter droplets. This same model was then compared to the experimental assessment of infiltration lengths reached under different process conditions. Evidence of partial evaporation of binder solvents during the infiltration process was also provided in this work.

This study has shown that the process parameters play a key role not only in the interaction between infiltrated volumes of consecutive layers, but also in the powder bed porosity. Furthermore, the control of these two factors was correlated to the higher mechanical strength of the cured samples as well as the dimensional deviations of the printed parts from the original CAD file. The achieved results are promising for the increase of the size of future parts, all without distortion and with accurate dimensions.