Binder Jet 3D Printing Research Articles

Coarse cemented carbide produced via binder jetting 3D printing

Until recently, cemented carbide produced via Binder Jetting 3D Printing (BJ3DP) resulted in microstructures with mixed WC grain size. Those materials exhibit excellent hardness and wear resistance but have transverse rupture strength that is lower than the strength of cemented carbide with a uniform grain size. The present investigation details the development of BJ3DP coarse tungsten carbide (WC-12%Co and WC-10%Co) that displays a sintered microstructure with uniform WC grain size. The free flowable (Carney flow <12 s/200 g) spherical powders exhibit very good printability and can be sintered to full density under standard sinter-HIP conditions (temperature 1460 °C, pressure 50 bar). The sintered mechanical properties compare well against cemented carbides produced by powder metallurgy. Vickers hardness, transverse rupture strength, and fracture toughness (determined by the Palmquist method) are in the range HV30 1050–1119, 2231–2684 MPa, and 18.8–19.4 MPa·m1/2, respectively. The wear properties were evaluated under abrasion and erosion using the ASTM B611 and ASTM G65 standard testing procedures. The wear resistance of the coarse BJ3DP cemented carbides compares well against conventionally produced cemented carbide. Parts over a wide range of sizes (from <1 g to 9 kg) and geometric complexities have been successfully printed and sintered with the new materials.

The Evaluation and Exploration of Piezoelectric Parameter Optimization for Droplet Ejection in Binder Jet 3D Printing Drugs.

Since the first three-dimensional (3D) printed drug was approved by the Food and Drug Administration in 2015, there has been a growing interest in using binder jet 3D printing (BJ-3DP) technology for pharmaceuticals. However, most studies are still at an exploratory stage, lacking micromechanism research, such as the droplet ejection mechanism, the effect of printhead piezoelectric parameters on inkjet smoothness and preparation formability. In this study, based on the inkjet printing and observation platform, the Epson I3200-A1 piezoelectric printhead matched to the self-developed BJ-3DP was selected to analyze the droplet ejection state of self-developed ink at the microlevel with different piezoelectric pulse parameters. The results showed that there was a stable inkjet state with an inkjet pulse width of 3.5 μs, an ink supply pulse width of 4.5 μs, and a jet frequency in the range of 5000-19,000 Hz, ensuring both better droplet pattern and print accuracy, as well as high ejection efficiency. In conclusion, we performed a systematic evaluation of the inkjet behavior under different piezoelectric pulse parameters and provided a good idea and case study for the optimization of printhead piezoelectric parameters when BJ-3DP technology was used in pharmaceuticals.

Binder Jet 3D Printing of 316L Stainless Steel: Orthogonal Printing and Sintering Process Optimization

Binder jet 3D printing (BJ3DP) is an additive manufacturing technique that uses a liquid binder to selectively deposit powder layer by layer to fabricate 3D parts followed by sintering. Herein, the printing parameters, sintering temperature, and holding time of 316L stainless steel (SS) materials produced by BJ3DP technique are systematically investigated. Based on the L9 orthogonal experimental design, the green parts can achieve the highest relative density of ≈55.9%, when the layer thickness, binder saturation, and roller traverse speed are 150 μm, 35%, and 100 mm s−1, respectively. Five green parts printed using the optimal parameters are subsequently sintered under different temperatures and holding time. All the as‐sintered samples consist of a primary γ‐Fe phase and a small amount of δ‐ferrite phase. After sintering at 1435 °C for 7.5 h, the as‐sintered samples obtain the highest relative density of ≈92.1% along with the most excellent mechanical properties, displaying ultimate tensile strength of ≈558 MPa and an elongation of ≈41%. The mechanical properties of these samples sintered at 1435 °C for 7.5 h are also superior to those of the annealed 316L SS in ASTM A276/A276M‐17.

Structured approach for designing drug-loaded solid products by binder jetting 3D printing

Additive manufacturing allows for designing innovative properties to pharmaceutical products. Binder jetting (BJ) 3D printing is one of the key techniques within innovative manufacturing. In this study, a structured approach according to the Quality by Design (QbD) principles was implemented to explore the factors affecting fabrication of drug-loaded products produced by BJ 3D printing. The investigated factors included the weight ratio of binder in primary powder and the process parameters related to printing (layer thickness and number of layers). Critical quality attributes, namely disintegration time, tensile strength, friability, dimensions (diameter and height accuracies), residual water content, weight and drug loading were determined based on the quality target product profile of a tablet analogue. The experimental results with a 2-level full factorial design were modeled by multiple linear regression. It was found that binder content was an important factor determining the integrity of the printed products, and the formation of the microstructure of the product was affected by multiple material properties and process parameters. QbD is a systematic and effective approach providing mechanistic understanding of BJ 3D printing and allowing for an efficient design of products with the desired quality.

Coating of Primary Powder Particles Improves the Quality of Binder Jetting 3D Printed Oral Solid Products

Binder jetting (BJ) 3D printing is especially suitable for the fabrication of an orodispersible solid dosage form, as it is an efficient way to avoid the use of mechanical forces typical for compaction-based processes. However, one of the existing challenges related to pharmaceutical applications of BJ is the relatively high amount of binder needed in the primary powder to ensure the sufficient mechanical strength of printed products. In this study, a strategy based on pre-processing with a thin layer coating was explored. With this strategy, the matrix particles (lactose monohydrate) of the primary powder for BJ 3D printing were coated with the binder (polyvinylpyrrolidone, PVP). The investigated compositions of the primary powder contained PVP at three levels, namely, 10 %, 15% and 20% (w/w). The primary powder compositions were prepared with or without the coated lactose powder, and they were subsequently 3D BJ printed into oral solid products with paracetamol as a model active drug substance. The presence of coated lactose in the primary powder increased the interparticulate interactions in the BJ 3D printed products. Especially for the composition with a relatively small amount of binder (i.e., 10% and 15% w/w PVP in the primary powder), the use of coated particles significantly improved the resistance to crushing and decreased the disintegration time of printed products. In conclusion, thin layer coating is an effective way to pre-process primary powder particles for BJ 3D printing of oral solid products.

Binder Jetting 3D Printing of Magnesium Oxychloride Cement-Based Materials: Parametric Analysis of Manufacturing Factors

Powder-bed binder jet 3D printing is a flexible method for producing magnesium oxychloride (MOC)-based articles. Despite the great potential of this additive manufacturing technology for producing free-form MOC cement-based components, the influence of processing factors on final material performance has not yet been investigated and no general models exist for the selection of proper parameters with the desired quality. In the present work, the effect of six key manufacturing factors on the modulus of rupture of MOC cement-based components was studied, using an analysis of variance. The parametric analysis revealed that the material’s strength was strongly influenced by three process inputs: particle size, the amount of binder, and layer thickness. The amount of binder was determined by the “rate of voxel” and the “powder-bed density” and required precise control during the printing process. The introduced quadratic regression model can assist operators in selecting a combination of binder jet process inputs to achieve predetermined final material performance.

Multi-scale characterization of supersolidus liquid phase sintered H13 tool steel manufactured via binder jet additive manufacturing

Additive manufacturing (AM) of H13 tool steel by binder jet 3D printing (BJ3DP) followed by pressureless supersolidus liquid phase sintering (SLPS) provides a low-cost alternative manufacturing method for components with intricate geometric features. However, the microstructure-mechanical property relationships for BJ3DP-SLPS produced H13 tool steel are not well understood, which makes it challenging to develop printing and post-processing methods that maximize part performance. In this work, we leverage atom probe tomography and transmission electron microscopy along with thermodynamic calculations to rationalize the microstructure-mechanical property relationships in as-sintered BJ3DP H13 tool steel. We report for the first time, the presence of a continuous eutectic film-like carbide in H13 along with the more commonly observed cuboidal MX carbides in the prior liquid channels of the microstructure. Further, atom probe tomography revealed the interconnected nature of the MX carbides that appear to be discrete in two-dimensional micrographs. These continuous eutectic carbides and interconnected MX carbides result in brittle failure of the material. Characterization of these microstructural features will be critical in developing appropriate post-processing heat treatments for the improved mechanical performance of BJ3DP H13.

Powder 3D Printing of Bone Scaffolds with Uniform and Gradient Pore Sizes Using Cuttlebone-Derived Calcium Phosphate and Glass-Ceramic.

The pore geometry of bone scaffolds has a major impact on their cellular response; for this reason, 3D printing is an attractive technology for bone tissue engineering, as it allows for the full control and design of the porosity. Calcium phosphate materials synthesized from natural sources have recently attracted a certain interest because of their similarity to natural bone, and they were found to show better bioactivity than synthetic compounds. Nevertheless, these materials are very challenging to be processed by 3D printing due to technological issues related to their nanometric size. In this work, bone scaffolds with different pore geometries, with a uniform size or with a size gradient, were fabricated by binder jetting 3D printing using a biphasic calcium phosphate (BCP) nanopowder derived from cuttlebones. To do so, the nanopowder was mixed with a glass-ceramic powder with a larger particle size (45–100 µm) in 1:10 weight proportions. Pure AP40mod scaffolds were also printed. The sintered scaffolds were shown to be composed mainly by hydroxyapatite (HA) and wollastonite, with the amount of HA being larger when the nanopowder was added because BCP transforms into HA during sintering at 1150 °C. The addition of bio-derived powder increases the porosity from 60% to 70%, with this indicating that the nanoparticles slow down the glass-ceramic densification. Human mesenchymal stem cells were seeded on the scaffolds to test the bioactivity in vitro. The cells’ number and metabolic activity were analyzed after 3, 5 and 10 days of culturing. The cellular behavior was found to be very similar for samples with different pore geometries and compositions. However, while the cell number was constantly increasing, the metabolic activity on the scaffolds with gradient pores and cuttlebone-derived powder decreased over time, which might be a sign of cell differentiation. Generally, all scaffolds promoted fast cell adhesion and proliferation, which were found to penetrate and colonize the 3D porous structure.

Manufacturing process and mechanical properties of BJ3DP tungsten heavy alloy components

Binder jetting 3D printing (BJ3DP) is an emerging technology that can enable the production of tungsten heavy alloy (WHA) parts of great geometric complexity. Despite its promise, the industrial use of BJ3DP is today hindered by two shortcomings: (i) Printed parts have low strength in the as-cured state, and (ii) the mechanical properties of the sintered parts are poor when sintered using standard sintering practice.This study was carried out to address those shortcomings. We introduce a new WHA powder for BJ3DP and compare it to existing powders [1]. Physical properties (flow, apparent density, size distribution) and the green strength after BJ3DP are reported.Sintering and microstructural evolution differences between the new WHA powder, existing WHA powders for BJ3DP and conventional press-and-sinter WHA powders were investigated. Good densification during the early stages of sintering enabled the sintering of the new powder to full density. After sintering, mechanical properties of the printed specimens were evaluated and compared to the properties of cold isostatically pressed WHA specimens using conventional powder blends with similar chemistry.The new powder has superior green strength in the as-printed condition and is therefore a better candidate for the manufacturing of complex parts. It also sinters much faster than currently available powders and achieves mechanical properties that match those of conventionally processed WHA.

Additive Manufacturing of Solid Products for Oral Drug Delivery Using Binder Jetting Three-Dimensional Printing

Binder jetting (BJ) three-dimensional (3D) printing is becoming an established additive manufacturing technology for manufacturing of solid products for oral drug delivery. Similar to traditional solutions based on compaction of powder mixture, successful processing of BJ products requires control of bulk powder properties. In contrast to traditional compaction-based process, BJ 3D printing allows for flexible modifications on microstructure, material composition and dose in the printed pharmaceutical products. Currently, systematic strategies for selecting excipients and optimizing the printing process have not been fully established. To address this challenge, a summary of the published work and selected patent literature around BJ 3D printing to fabricate pharmaceutical solid products for oral administration purposes is presented. First, an overview of characteristics of printed products as a part of the product design and a description of the commonly used excipients and active pharmaceutical ingredients is given. The critical powder and ink properties, as well as physical geometries and inner structures of a final product, are discussed in term of the mechanisms that determine the formation of a printed solid product and finally the quality of this product. This review is also summarizing the technical features of printers, printheads, and the critical considerations for post-processing procedures. BJ 3D printing is one of the most promising additive manufacturing technologies for mass customization of pharmaceutical products.

Multi response optimization for compressive strength, porosity and dimensional accuracy of binder jetting 3D printed ceramic bone scaffolds

Additively manufactured bone scaffolds have been gaining attention of researchers for past couple of years. Besides biocompatibility, bone scaffolds are expected to exhibit a good combination of porosity, mechanical strength and dimensional accuracy for success of the bone tissue engineering. This paper presents a multi objective optimization for additively manufactured ceramic porous bone scaffold prototypes using hybrid Taguchi based Grey relational analysis approach. Five process parameters namely, layer thickness (LT), build orientation (BO), build position (BP), binder saturation (BS) and delay time (DT) of binder jetting 3D printing process have been optimized for three response parameters, namely compressive strength (CS), measured porosity (MP) and dimensional accuracy (DA) of fabricated porous scaffolds. Initially, experiments are designed and performed as per the Taguchi's L27 orthogonal array and signal-to-noise (S/N) ratios for all the experiments have been calculated. Then Grey relational grades (GRGs) of S/N ratios are computed. Main effect plots for means and S/N ratios of GRGs reveals LT1, BO1, BP2, DT1 and BS2 as optimum levels of process parameters for CS, MP and DA. Analysis of variance of GRGs suggests that BO (40.42%) the most, LT (29.81%) the second most and DT (5.19%) the least significant parameter in affecting the response parameters. The value of GRG at optimum levels of the parameters have been predicted using the mean GRG model and liner regression model. Finally, a confirmation test is performed and result has been compared with the predicted values. A deviation of 3.93% (mean GRG model) and 3.89% (regression model) have been observed between experimental and predicted values of GRGs.

Shape retention of cemented carbide prepared by Co melt infiltration into un-sintered WC green parts made via BJ3DP

Direct melt infiltration does not produce sintered closed holes and considerably reduces the time required for preparation compared with pre-sintered WC skeleton followed by melt infiltration of Co. However, it may lead to alloy collapsing and deformation. In this study, WC and Co green parts were prepared via binder jet 3D printing. The two parts were stacked layer by layer then subjected to melt infiltration to prepare a WC–Co series of cemented carbides. The aim was to investigate the shape retention, infiltration conditions, and properties of the alloy after the equal distribution of Co and the direct infiltration of the Co melt into the WC green parts without pre-sintering. The effect of different Co amounts on the product was also studied. Results showed that the carbide prepared through direct melt infiltration of WC green parts without pre-sintered skeletons displayed excellent shrinkage and properties. The shrinkage of the prepared cemented carbide with a Co content of about 25 wt% was within 3% in all directions. The relative density, hardness, and fracture toughness of the alloy reached 96.65%, 11.5 GPa, and 23.5 Mpa m1/2, respectively. This work provides a simplified, and high-shape-retention method for other alloys that can be prepared through melt infiltration.

Binder Jet 3D Printing of Magnesium Oxychloride Cement-Based Concrete: A Framework to Design the Rate of Voxel

The present work addresses the powder bed binder jet 3D printing as an additive manufacturing process for cement-based materials in the constructions industry. Features are created through the interaction among the droplets of the liquid binding agent and the layered powder bed. The printhead movement over the powder bed at a given feed rate forms voxels and single-lines from the coalesce of successive droplets and adjacent lines are consolidated to create the designed cross-section. Here, statistical models have been developed to study the effect of printing parameters (aggregate particle size, feed rate, velocity of powder spread, pressure of the fluid and nozzle diameter) on the resultant dimension of a single printed line, using a factorial design of experiment. The hardware of the 3D printer, the physical properties of the powder blend and binder are initial constraints for designing voxels. Linear regression models of significant parameters are presented. Pressure is one of the most significant factors, it has a profound effect on the granule formation mechanism. Cubic samples printed with higher pressure level are characterized by higher residual porosities from crater channels during the printing process. The results demonstrate a fundamental understanding of the binder–powder interaction for cementitious materials which can be leveraged to determine the minimum printable feature with required dimensional accuracy, based on the chosen process parameters.

Fabrication of a Stainless-Steel Pump Impeller by Integrated 3D Sand Printing and Casting: Mechanical Characterization and Performance Study in a Chemical Plant

The emergence of additive manufacturing is renovating the landscape of available production technologies. In this paper, we describe the fabrication of a closed vane pump impeller (ϕ 206 mm, height 68 mm, weight 4 kg) by binder jetting 3D printing of a sand mould followed by casting using stainless steel 316 to create an identical copy of a part in service in a chemical plant in Tarragona, Spain. The original part was reverse engineered and used to create a sand mould by binder jetting 3D printing on which new impellers were fabricated by casting. Metallographic studies showed an austenitic matrix with 6.3% of ferritic phase and 40 μm × 8 μm ferrite grains without precipitated carbides. The impeller was put into operation in a centrifugal pump at a polyol/polyglycol plant belonging to Dow Chemical Ibérica SL from October 2020 to April 2021. Process variables related to the pump behaviour were compared with the same variables obtained in previous cycles with the original impeller for three different product viscosities (30, 180, and 500 cSt). At 500 cSt, the average current consumption was 9.34 A as compared with the 9.41 A measured with the original impeller. Similarly, the pump pressure remained essentially constant during process operation with both impellers (3.97 bar with the new impeller vs. 3.99 bar with the old). Other monitored parameters (product flow, tank level) were similar in both cases, validating the fabrication strategy from an operational point of view. This work further demonstrated that the implementation of additive manufacturing technologies in chemical process engineering is a useful solution to fabricate spare parts that are difficult to replicate with other technologies, providing consequent economic benefits.

Influence of initial relative densities on the sintering behavior and mechanical behavior of 316 L stainless steel fabricated by binder jet 3D printing

Compared with other 3D printing methods, binder jet 3D printing (BJ3DP) shows the great potential for obtaining large-scale complex parts with high efficiency and low cost. However, understanding the sintering behavior of powders is one of the challenging topics in BJ3DP. In this work, on the basis of the thermo–elasto–viscoplastic constitutive law model, the sintering behavior of 316 L stainless steel (316 L SS) cuboids prepared by BJ3DP with different initial relative densities (relative densities of green parts), i.e., 49.5%, 51.5% and 53.5%, was investigated via finite-element numerical simulations. It suggested that the shrinkage decreased as the initial relative density increased, resulting from that a higher initial relative density would provide higher sintering stress. Additionally, precise shrinkage and final relative densities of the BJ3DP samples were quantitatively predicted via numerical simulations, and the simulated results were in good agreement with experimental results. According to the experimental results, a final relative density of ~98.7% could be achieved in the BJ3DP 316 L SS sample with an initial relative density of 53.5% after sintering, showing a yield strength of ~308 MPa and an ultimate tensile strength of ~601 MPa along with a total elongation of ~59.4%.

A general fruit acid chelation route for eco-friendly and ambient 3D printing of metals

Recent advances in metal additive manufacturing (AM) have provided new opportunities for prompt designs of prototypes and facile personalization of products befitting the fourth industrial revolution. In this regard, its feasibility of becoming a green technology, which is not an inherent aspect of AM, is gaining more interests. A particular interest in adapting and understanding of eco-friendly ingredients can set its important groundworks. Here, we demonstrate a water-based solid-phase binding agent suitable for binder jetting 3D printing of metals. Sodium salts of common fruit acid chelators form stable metal-chelate bridges between metal particles, enabling elaborate 3D printing of metals with improved strengths. Even further reductions in the porosity between the metal particles are possible through post-treatments. A compatibility of this chelation chemistry with variety of metals is also demonstrated. The proposed mechanism for metal 3D printing can open up new avenues for consumer-level personalized 3D printing of metals.

Characterization of radiation damage in 3D printed SiC

• High-purity SiC composites fabricated by additive manufacturing were irradiated. • Radiation-induced defects are easily observed in α-SiC particles but not CVI matrix. • Defect swelling measured by STEM-EELS is similar in α-SiC particles and CVI matrix. • Defect types and swelling are consistent with other forms of nuclear-grade SiC. • Interface denuded zone reveals sink strength bias and relative defect-type mobility. The SiC fuel matrix for advanced gas-cooled high temperature reactors as part of the Transformational Challenge Reactor program serves as the fuel particle container structure, a barrier to fission gas release, and a heat transfer medium. Its performance is particularly important because the fuel matrix must demonstrate good structural stability and thermal behaviors. An additive manufacturing methodology combining a binder jet 3D printing process with chemical vapor infiltration (CVI) for the production of SiC was recently developed. In this study, post irradiation examination by transmission electron microscopy shows that defect accumulation within the printed particles is very similar to other forms of high-purity SiC. However, damage accumulation was not directly observed in the CVI matrix because black spot damage and dislocation loops are difficult to image within the nanoscale highly faulted CVI matrix and because interstitial defects may rapidly annihilate at the stacking faults. Therefore, electron energy loss spectroscopy (EELS) analysis was used to analyze defect swelling in both the printed particles and the CVI matrix. The EELS analysis helped reveal that the radiation-induced swelling in the CVI matrix is similar to that of the printed SiC particles. This work shows that 3D printed SiC has behavior that is comparable to SiC processed by other means and that 3D printing could serve as a suitable processing technique for high-purity SiC for nuclear applications.

Review of binder jetting 3D printing in the construction industry

Review of binder jetting 3D printing in the construction industry

Evaluation of the Mechanical and Photocatalytic Properties of Tio2-Reinforced Cement-Based Material in Binder Jet 3d Printing

Evaluation of the Mechanical and Photocatalytic Properties of Tio2-Reinforced Cement-Based Material in Binder Jet 3d Printing

Binder Jet 3d Printing of Biomedical Grade Ti-6al-4v Alloy: The Role of Particle Size, Microstructural Features, and Mechanical Properties

Binder Jet 3d Printing of Biomedical Grade Ti-6al-4v Alloy: The Role of Particle Size, Microstructural Features, and Mechanical Properties