Powder reusability in metal binder jetting

Metal Binder Jetting (MBJ) is a potential mass-production additive manufacturing technique that enables faster production of complex structures with isotropic material properties. In MBJ, the quality of parts is heavily influenced by the powder characteristics, and even small variations in powder feedstock can result in poor quality parts. Powder management is crucial in this technology because the powder is processed in a high humidity environment in the machine, and the binder is mixed with the powder as well. In this paper, the characteristics of 316l and 17-4PH stainless steel powders under the machine atmosphere and their reusability are studied in detail. Powder samples were taken from the build box at a fixed interval of time and their moisture content, packing density and morphology were analysed through scanning electron microscopy (SEM). Based on the results obtained, it was observed that moisture content of the powder increases with the time up to a few hours when it gets constant. Additionally, it was observed that after the first reuse cycle of the powder, the finest powder particles almost disappear, which may have a detrimental effect on the density of the generated parts. Finally, the recycling of broken green parts was also investigated by means of a new approach. Taking into account that broken green parts are generally scrapped in MBJ, the recyclability of this material could reduce the high material costs related to the process.