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In this work, a tung oil-based thermosetting resin was synthesized via free radical polymerization and reinforced with thirteen different types of sand. The viability of this process inspired the adaptation of the resin for its use as a binder material in binder jetting, an additive manufacturing process. Firstly, it was shown that the resin could have its initial viscosity (~0.33 cP) increased upon heating to attain values compatible to existing printing systems. The curing kinetics of the resin was assessed via dielectric analysis (DEA), combining the utilization of heat and ultraviolet (UV) light, showing that a resin with a viscosity of 10 cP can be fully cured after 250 min at 90 ◦C, or 300 min at 75 ◦C, both under a 365 nm light exposure. Preliminary binder-jet tests successfully provided a solid object, which was post-cured, resulting in a hard specimen. The results presented herein suggest that the tung oil-based resin in question is a suitable bio-based binder for binder-jet 3D-printing applications. The novelty of the work reported lies in the conversion of an already established and effective bio-based thermosetting resin into a versatile photocurable binder that can be irrestrictively used with unsorted sands of different composition, making this technology broadly applicable to different isolated regions, using local resources available. The technology presented herein is potentially transformative and impactful, as binder jetting is typically associated to extremely well-sorted particles. 

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. 

Additive manufacturing (AM) presents unique challenges to the nondestructive testing community, not least in that it requires inspection of parts with complex forms that are not possible using subtractive manufacturing. The drive to use AM for parts where design approaches include damage tolerance and retirement-for-cause with high quality and where safety criticality imposes new QA/QC requirements is growing. This article reviews the challenges faced to enable reliable inspection and characterization in metal powderbased AM processes, including issues due to geometric and microstructural features of interest, the limitation on existing and emerging NDT techniques, and remaining technology gaps. The article looks at inspection from powder to finished part, but focuses primarily on monitoring and characterization during the build. In-process, quantitative characterization and monitoring is anticipated to be transformational in advancing adoption of metal AM parts, including offering the potential for inprocess repair or early part rejection during part fabrication. 

The ability of Additive Manufacturing (AM) processes to ensure delivery of high quality metal-based components is somewhat limited by insufficient inspection capabilities. The inspection of AM parts presents particular challenges due to the design flexibility that the fabrication method affords. The nondestructive evaluation (NDE) methods employed need to be selected based on the material properties, type of possible defects, and geometry of the parts. Electromagnetic method, in particular Eddy Current (EC), is proposed for the inspections. This evaluation of EC inspection considers surface and near-surface defects in a stainless steel (SS) 17 4 PH additively manufactured sample and a SS 17 4 PH annealed plates manufactured traditionally (reference sample). The surfaces of the samples were polished using 1 micron polishing Alumina grit to achieve a mirror like surface finish. 1.02 mm (0.04”), 0.508 mm (0.02”) and 0.203 mm (0.008”) deep Electronic Discharge Machining (EDM) notches were created on the polished surface of the samples. Lift off and defect responses for both additive and reference samples were obtained using a VMEC-1 commercial instrument and a 500 kHz absolute probe. The inspection results as well as conductivity assessments for the AM sample in terms of the impedance plane signature were compared to response of similar features in the reference sample. Direct measurement of electromagnetic properties of the AM samples is required for precise inspection of the parts. Results show that quantitative comparison of the AM and traditional materials help for the development of EC technology for inspection of additively manufactured metal parts.