Advanced core-shell printing method for binder-free metal components: modifying sintering characteristics in binder jetting

Purpose This study aims to present an innovative additive manufacturing technique for metal components, using a binder jetting based method designed to facilitate fully automated depowdering and improve mechanical properties by eliminating binder from the part body. Design/methodology/approach Unlike conventional metal binder jetting (MBJ), this method does not introduce a binder into the body of the component. Instead, a binder containing anti-sintering agent is selectively applied to form a thin shell layer enveloping the part. The anti-sintering agent prevents powder particles from neck formation during preliminary heat treatment (pre-sintering). Following the pre-sintering step, the core of the component gains strength, whereas the outer shell remains comparatively weak. The principal advantage of this approach-beyond enabling fully automated depowdering and the fabrication of small intricate components via MBJ is the absence of binder within the component body, resulting in reduced porosity and, consequently, superior mechanical properties. This also prevents debinding problems. Findings After pre-sintering, specimens produced using this binder system (polyvinylpyrrolidone and magnesium nitrate) demonstrate a flexural strength of 5 MPa, while those made from pure 316 L stainless steel powder without anti-sintering additives exhibit a much higher flexural strength of 40 MPa. This strength difference supports the use of higher depowdering forces for automated processing without structural compromise. Originality/value This shell-only binder strategy removes binder from the component body, lowering porosity and improving mechanical performance relative to conventional MBJ. By enabling robust, fully automated depowdering of small, intricate parts while avoiding debinding issues, it provides a scalable route to more reliable industrial MBJ workflows.