An official website of the United States government
In binder jet additive manufacturing (BJAM), uniformity and density of the powder layer impact green part quality. This study investigates the printability of unrefined sand using counter-roller spreading. Altair EDEM, a high-performance software powered by the Discrete Element Method (DEM), was used to simulate the BJAM process to evaluate powder bed homogeneity and density under various operating conditions, including roller rotational speed, traverse speed, powder layer thickness, and roller diameter. Utilizing high-performance computing (HPC) and graphics processing unit (GPU) clusters, time-efficient, and more realistic, simulations were performed simulating 300,000 grains. Detailed DEM simulations were executed by reconstructing representative particle shapes using two-dimensional images obtained using particle characterization equipment. The results highlight roller velocity and powder layer thickness as key determinants of sand spreadability. Optimal powder bed density (PBD) was achieved at a roller velocity of 20 mm/s with minimal deviation. A layer thickness exceeding 200 micrometers was found to prevent jamming and void formation, while percolation led to size segregation. The findings indicate that producing uniform and dense layers of unrefined sand is feasible but may incur trade-offs in print resolution and increased printing times. This work contributes to the advancement of sustainable and/or remote BJAM technologies, ensuring progress in both environmental sustainability and accessibility.
more »
« less
Discrete element analysis of powder spreading in binder jetting of raw Earth sediments
Binder jetting of minimally processed, locally sourced sediments offers a promising route toward sustainable additive manufacturing, but powder spreading of poorly sorted, irregular grains remains underexplored. This study uses high-fidelity Discrete Element Method (DEM) simulations to quantify how process parameters govern layer quality when spreading an unrefined sandy silt from the Gypsum Hills, Kansas, USA, with a counter-rotating roller. Twenty-five multi-sphere particle shapes were reconstructed from morphological measurements and used to simulate up to 300,000 interacting grains while systematically varying roller traverse speed, rotational speed, diameter, and layer thickness. Traverse speed and layer thickness emerged as the dominant controls on powder bed density and uniformity: the slowest traverse speed (20 mm/s) produced the highest density (~ 0.50) and lowest variability (~ 0.08), and layer thicknesses ≥ 120 μm were required to avoid jamming and obtain consistent packing. In contrast, roller diameter and rotational speed had only minor influence over the explored ranges. The simulations also revealed percolation-driven segregation, with fine particles preferentially settling beneath coarser grains. Comparison with an idealized spherical powder showed that the silt is intrinsically harder to spread, achieving lower density (0.51 vs. 0.59) and higher variability. These results demonstrate that binder jet processing of unrefined silt is feasible but favors slower spreading and thicker layers that may reduce throughput and resolution, and they provide process design guidelines and particle-scale insight for deploying raw earth feedstocks in sustainable binder jetting.
more »
« less
- PAR ID:
- 10674404
- Publisher / Repository:
- Springer Nature
- Date Published:
- Journal Name:
- The International Journal of Advanced Manufacturing Technology
- ISSN:
- 0268-3768
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Binder jetting is a powder bed additive manufacturing process where an object is created by depositing liquid binder onto the surface of powder, selectively binding particles in each layer. The quality of the as-printed parts is influenced not only by process parameters such as layer thickness, binder saturation, print speed, and drying time but also by the location within the build box. This study highlights the location-dependent nature of green density and dimensional accuracy in the as-printed samples, and the observed trends are thoroughly discussed. A conventional powder spreading using a single roller was compared with a double roller to maximize powder packing and bed uniformity prior to binder jetting process. The significance of these observations lies in their impact on densification behavior, shrinkage, and the final geometry of the printed part.more » « less
-
Powder bed compaction can be used to control powder bed density in binder jetting additive manufacturing. Applying a forward-rotating roller to the powder bed is one of the methods for powder bed compaction. Both the compaction rotation speed and compaction thickness are critical parameters affecting the powder packing density and resultant printed sample integrity. However, their joint effects have not been investigated for roller-compaction-assisted binder jetting. This paper reports an experimental study to investigate the effects of the compaction rotation speed and the compaction thickness on powder bed density and the printed sample quality (in terms of distortion and cracks). The experimental results showed that powder bed density was not affected by changing compaction rotation speed but was enhanced by increasing compaction thickness. Small compaction thickness did not cause any observable distortions or cracks in the printed samples at any compaction rotation speed. Large compaction thickness caused printed samples to distort and crack under specific conditions. At large compaction thickness, compaction rotation speed significantly affected both the direction and extent of the printed sample distortion. Samples with improved density and integrity were achieved in the center of the build platform at large compaction thickness and at a compaction circumferential speed larger than the compaction traverse speed. These results can help optimize binder jetting additive manufacturing for printed sample quality.more » « less
-
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.more » « less
-
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.more » « less
- Free Publicly Accessible Full Text
-
Accepted Manuscript
- Journal Article:
- https://doi.org/10.1007/s00170-025-17225-9
