Assessing the impact of binder saturation on print quality of binder jetted green samples of regular morphologies

Abstract

A pivotal process parameter in binder jetting additive manufacturing (BJAM) is binder saturation, defined as the volumetric ratio of binder deposited to voids within the powder bed. Improperly tailored binder saturation may lead to printing issues such as binder overspread, increased surface roughness, and layer delamination. These existing issues may be further exacerbated with the use of irregular morphological powders, which have a higher degree of interparticle friction and therefore tend to form powder beds with larger pores. This then slows down binder imbibition into the bed. This research will examine the effect of varying binder saturation on a regular (sphericity of 0.95) powder morphology and the resulting green part qualities using C18150 copper alloy powder. A metric used to assess quality is dimensional fidelity, evaluated using image processing techniques to compare designed vs. actual feature size of key geometric structures such as fine through holes and horizontal slots. Additionally, the green density of prints was evaluated with a precision balance and calipers on cubic samples. It was found that, for regular morphology powders, dimensional error did not scale with decreasing feature size. Thus, uniform compensation factors may be implemented into future CAD designs to improve dimensional accuracy.