High-speed X-ray imaging of droplet-powder interaction in binder jet additive manufacturing

• Published in: Additive manufacturing 2024-06, Vol.89 (C), p.104269, Article 104269
• Main Authors: Lawrence, Jacob E., Lawrence, Madi P., Fezzaa, Kamel, Clark, Samuel J., Crane, Nathan B.
• Format: Article
• Language: English
• Subjects: Binder Jetting; Binder-Powder Interaction; Inkjet; SS316L; Synchrotron X-ray Imaging
• ISSN: 2214-8604; 2214-7810
• DOI: 10.1016/j.addma.2024.104269

Binder jetting (BJ) is an additive manufacturing process that uses a powder feedstock in a layer wise process to print parts by selectively depositing a liquid binder into the powder bed using inkjet technology. This study presents findings from high-speed synchrotron imaging of binder droplet-interaction during the BJ printing process. A custom laboratory-scale BJ test platform was used for testing which enabled control of relevant process parameters including powder material, print geometry, spacing between droplets, powder bed density, and powder moisture content. Powder ejection was observed above the powder bed surface and powder relocation due to droplet impact was observed below the powder bed surface. Powder relocation was observed to be sensitive to powder material, powder bed density, powder bed moisture, droplet spacing, and print geometry. Increasing powder bed density was found to increase particle ejection velocity but reduce the total number of particles ejected. Process parameters that increase binder / moisture content in the powder bed were found to reduce powder ejection. The number of ejected powder particles was reduced for lower droplet spacings. Both powder ejection and powder relocation below the powder bed were reduced by treating the surface of the powder bed with a water/triethylene glycol (TEG) mixture before printing. Results from this study help to build understanding of the physical mechanisms in the BJ printing process that may contribute to formation of defects observed in final parts.