Manufacturability of overhang structures fabricated by binder jetting process

Due to the superior mechanical properties of metals and the inherent capability of additive manufacturing (AM) to fabricate complex structures, metal AM reveals a promising future in the industrial fields. Compared with other metal AM processes, Binder Jetting (BJ) process has potential of producing overhang structures without additional supports. This advantage of BJ process significantly enlarges the design freedom of complex metal parts with intricate overhang structures. However, it should be noted that there is still a certain manufacturing limitation of overhang structures for BJ process. Without the support of loose powder after the depowdering process, the green part is vulnerable to the inevitable external loads, such as self-weight. In this paper, a theoretical model has been proposed to evaluate the self-support capability of printed green parts after the depowdering process. A set of experiments has been designed to find the maximum normal stress that printed green parts can withstand. This proposed theoretical model can be used to predict manufacturability of overhang structure of any arbitrary shape. Based on this model, some design guidelines and future work are summarized at the end of this paper.