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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.
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This content will become publicly available on July 22, 2026
Powder bed non-uniformity investigations via discrete element modelling for binder jetting technology
In the binder jetting (BJ) process, as in most of powder bed additive manufacturing technologies, the powder is periodically recoated onto the substrate layer-by-layer. The elements of the current deposited layer corresponding to the part being manufactured are bonded together using a polymeric binder. In all cases that require a thermal process for sintering, the internal structure of the finished part is defined by the internal structure of the powder bed. This article focuses on the discrete element modelling (DEM) of various powder spreading methods during recoating and their impact on the powder bed structure particularly applied to binder jetting technology. The article demonstrates that despite the thinness of the deposited layers, they typically exhibit porosity and particle and pore size non-uniformities along the build-up direction. These irregularities contribute to the anisotropic sintering shrinkage observed in green BJ bodies during experiments. However, the experiments presented confirmed by modelling show that without binder deposition, the powder bed – except for a narrow surface layer – remains relatively uniform, regardless of the recoating method used. It is the binder injection into the porous structure of the powder bed that disrupts this homogeneity, locks in large surface pores, and exacerbates the effects of powder segregation during spreading. Finally, several strategies, explored via simulation, are proposed to reduce porosity variations during BJ: using a combined roller-wide blade method for powder spreading and a two-hopper approach, where each layer consists of small particles deposited over larger ones.
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- Award ID(s):
- 2119832
- PAR ID:
- 10617163
- Publisher / Repository:
- SAGE Publications
- Date Published:
- Journal Name:
- Powder Metallurgy
- ISSN:
- 0032-5899
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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