Jet 3D Printing Research Articles

Binder jet 3D printing of Mn–Zn ferrite soft magnet toroidal cores

Traditional powder processing methods for Mn–Zn ferrites limits design freedom and scalability of producing customized soft magnetic cores. In this work, binder jet 3D printing techniques were applied to commercially available Mn–Zn ferrite powders and toroidal cores were successfully fabricated. As-printed Mn–Zn ferrite powders were sintered at different temperatures between 1300 and 1400 °C, resulted in an optimized single-phase spinel at 1350 °C. Microstructural characterization revealed high porosity remained for binder jetted materials and various magnetic property measurements were performed on sintered cores. Despite high porosity, the saturation moments normalized by mass remained similar between binder jetted and traditionally compacted samples. Two-winding method measurements indicated a large demagnetizing field for binder jetted samples. Effective medium theory model was used to estimate the effect of remnant porosity on measured magnetic permeabilities. Importance of novel concepts to successfully realize dense cores through additive manufacturing pathways such as binder jetting is highlighted.

Sintering densification mechanism of binder jet 3D printing 316L stainless steel parts via dimensional compensation technology

The dimensional compensation technology can achieve high dense metal parts with precise dimensions for binder jet 3D printing (BJ3DP). In this study, two models (cuboid and gear) of BJ3DP 316L stainless steel (BJ3DP316LSS) parts were established. Numerical simulation and experimental volume shrinkage of the BJ3DP316LSS sintered parts via dimensional compensations technology were investigated. When the dimensional compensation coefficient was set as 1.25, the BJ3DP316LSS cuboids and gears exhibited high densification as 99.6% and 99.4%, respectively. The experimental dimension deviation rates of cuboid and gear parts after dimensional compensations ranged from −3.56% to −0.15% and from 0.89% to 3.42%, respectively. Due to twinning-induced plasticity mechanism, the BJ3DP316LSS sintered gear part via dimensional compensation technology exhibited high hardness (∼139 HV), high yield strength (∼249 MPa), high ultimate tensile strength (∼546 MPa) and excellent elongation (∼62%), which are higher than those of the reported 316LSS samples.

Effects of printing parameters on the mechanical properties of sand molds produced by a novel binder jetting 3D printer

Effects of printing parameters on the mechanical properties of sand molds produced by a novel binder jetting 3D printer

Mechanical and Fatigue Properties of Ti-6Al-4V Alloy Fabricated Using Binder Jetting Process and Subjected to Hot Isostatic Pressing.

Binder jetting 3D printing is an additive manufacturing technique based on the creation of a part through the selective bonding of powder with an adhesive, followed by a sintering process at high temperature to densify the material and produce parts with acceptable properties. Due to the high initial porosity in the material after sintering, which is typically around 5%, post-sintering treatments are often required to increase the material density and enhance the mechanical and fatigue properties of the final component. This paper focuses on the study of the benefits of hot isostatic pressing (HIP) after sintering on the mechanical and fatigue properties of a binder jetting Ti-6Al-4V alloy. Two different HIP processes were considered in this study: one at 920 °C/100 MPa for 4 h, and a second at a higher pressure but lower temperature (HIP-HPLT) at 850 °C/200 MPa for 2 h. The effects of the HIP on the densification, microstructure, mechanical behavior, and fatigue properties were investigated. The results show that the HIP-HPLT process produced a significant increase in the mechanical and fatigue properties of the material compared with the as-sintered parts and even with the conventional HIP process. However, the fatigue and fracture micromechanisms suggest that the oxygen content, which resulted from the decomposition of the binder during the sintering process, played a critical role in the final mechanical properties. Oxygen could reduce the ductility and fatigue life, which deviated from the behavior observed in other additive manufacturing techniques, such as powder bed fusion (PBF).

Fabrication of broadband wave-transparent porous Si3N4 ceramics by powder hybrid mechanism combined with binder jetting 3D technology

Binder jetting 3D printing is a novel methodology for fabricating broadband wave-transparent porous Si3N4 ceramics, but it faces challenges in low bending strength post-sintering, which impedes its broader application. This study proposed a hybrid mechanism by mixing Si and Si3N4 powders to surmount this challenge, and systematically scrutinized the mechanical and dielectric performance evolution of sintered samples at 1700–1800 °C after investigating nitride rules. Adding Si powder notably improved the bending strength, while retaining superior wave-transparent performance. When Si: Si3N4 was 50:50, at 1750 °C and 1800 °C, the bending strength was enhanced by 2.9 and 2.5 times compared to no Si powder addition. The real permittivity was consistently below 3.3. This work presented an effective methodology for modulating the overall performance of porous Si3N4 ceramics.

Aerosol jet 3D printing of gold micropillars and their behavior under compressive loads

Three-dimensional (3D) gold microarchitectures such as micropillars, microwires, and microlattices are used in applications such as implantable biosensors, microelectronic circuits, and catalytic devices. Additive Manufacturing (AM) is being explored to create such structures as lithography is more suitable to fabricate 2D or planar architectures. In this work, we use Aerosol Jet (AJ) nanoprinting, a jetting-based AM technique, to demonstrate fabrication of gold micropillars via stacking of nanoparticles and sintering them at temperatures ranging from 300°C to 900°C. We first demonstrate that AJ printed 2D planar films and 3D micropillars exhibit a different grain size distribution, even if they are printed and sintered under identical conditions. This unusual observation indicates that specific AM technique and structures are important in determining their grain structure, which affects their mechanical behavior. The AJ printed 3D gold micropillars are fabricated with aspect ratios up to 10:1 and sintered from lower to higher temperatures, to yield porosities ranging from 15 % to 2 %, and average grain sizes from 25 nm to 1.7 µm, respectively. Micropillars sintered at lower temperatures exhibit a brittle behavior with higher yield strength despite having a higher porosity but with smaller grain sizes, and vice versa. These results indicate that the 3D geometry of AJ printed architectures dictates the grain size evolution, and hence the mechanical properties. Further, the grain size dominates over porosity in determining the micropillar deformation. These results provide important design guidelines for 3D printed microarchitected structures fabricated via jetting-based AM techniques.

Machine learning enables electrical resistivity modeling of printed lines in aerosol jet 3D printing

Among various non-contact direct ink writing techniques, aerosol jet printing (AJP) stands out due to its distinct advantages, including a more adaptable working distance (2–5 mm) and higher resolution (~ 10 μm). These characteristics make AJP a promising technology for the precise customization of intricate electrical functional devices. However, complex interactions among the machine, process, and materials result in low controllability over the electrical performance of printed lines. This significantly affects the functionality of printed components, thereby limiting the broad applications of AJP. Therefore, a systematic machine learning approach that integrates experimental design, geometrical features extraction, and non-parametric modeling is proposed to achieve printing quality optimization and electrical resistivity prediction for the printed lines in AJP. Specifically, three classical convolutional neural networks (CNNs) architectures are compared for extracting representative features of printed lines, and an optimal operating window is identified to effectively discriminate better line morphology from inferior printed line patterns within the design space. Subsequently, three representative non-parametric machine learning techniques are employed for resistivity modeling. Following that, the modeling performances of the adopted machine learning methods were systematically compared based on four conventional evaluation metrics. Together, these aspects contribute to optimizing the printed line morphology, while simultaneously identifying the optimal resistivity model for accurate predictions in AJP.

Preparation of high-density green body based on binder jetting 3D printing using spheroidized SiC powder

Silicon carbide (SiC) ceramic stands as a critical material in the realm of high-performance engineering ceramics. However, Crafting SiC ceramics with intricate structures and superior mechanical properties presents notable challenges in shaping, sintering, and processing. Binder jetting (BJ) additive manufacturing has the outstanding advantages of high forming efficiency and no thermal deformation, especially suitable for printing complex structure SiC components.; however, BJ printed green bodies often exhibit low density, resulting in high residual silicon content and diminished strength of the final components. In this work, we introduce a novel strategy to fabricate high-strength SiC components with complex geometries by improving the density of printed SiC green bodies. This method involves modifying the morphology of SiC powder through the molten salt method to increase the density of BJ 3D printed green bodies from 1.24 ± 0.13 g/cm³ to 2.01 ± 0.03 g/cm³, followed by a reactive melt infiltration process. The resulting RB-SiC ceramics display exceptional flexural strength, averaging 280.60 ± 33.05 MPa, and an elastic modulus of 294.67 ± 4.90 GPa. These values represent some of the highest for flexural strength and elastic modulus reported among 3D-printed SiC composites. With its robust mechanical performance and streamlined fabrication process, this strategy holds substantial promise for the production of structural SiC ceramics.

Increasing strength properties in sinter-based additive manufacturing of SS316L via metal material jetting of sub-micron powders

Metal Binder Jetting (MBJ) 3D printing is an attractive additive manufacturing (AM) method for high volume production of metals and ceramics. However, the widespread use of MBJ has been stymied by longstanding challenges in reduced strength properties compared with traditional wrought and laser-based AM materials. In this study, we leveraged novel “drop-on-demand” Metal Material Jetting (MMJ) of sub-micron powders to fabricate SS316L samples. These samples were subjected to dilatometry, mechanical testing, and correlative materials characterization and compared to metal binder jet (MBJ) SS316L to evaluate differences in process-structure-property relationships between the two processes. Overall, MMJ SS316L possessed an average tensile yield and ultimate tensile strength of 312 ± 84 MPa and 640 ± 38 MPa respectively, greatly exceeding MBJ SS316L in the literature due to the formation of fine microstructures with an average grain size of 2.4μm. Importantly this led to significant Hall-Petch strengthening but also considerably lower average failure strains (15.5 ± 4.8 %). The process-microstructure-property relationships facilitating microstructural evolution in MMJ are discussed and further elucidated using an isotropic pressure-less viscous sintering model. Results of this model show that, although densification behaviors in MMJ were largely similar to those in MBJ, MMJ samples possessed over three-fold increase in sintering stress, defined the change in free surface energy with respect to the volumetric shrinkage, and ∼31 % reduction in grain growth due to the employment of sub-micron size powders. Overall, these results show the promise of MMJ AM for structural metals and suggest that both microstructure (and ultimately strength) of MMJ materials can be further tuned by controlling the overall sintering process.

Microstructure and properties of tungsten‐40 wt.–% copper composites fabricated by binder jet 3D printing

AbstractIn this work, the tungsten‐copper composites were fabricated by binder jet 3D printing technology. The effects of different printing layer thicknesses (50 μm to 100 μm) on the green density and green strength were investigated. Then, under the optimal layer thickness, the effects of different sintering temperatures (1300 °C to 1600 °C) on the microstructure and densification of tungsten‐40 wt.–% copper composites were studied. The experimental results showed that when the printing layer thickness was set as a lower value (50 μm), the tungsten‐40 wt.–% copper green part had the best strength and its density reached a maximum value of 60.73 %. After sintering for green parts printed with 50 μm layer thickness, the relative density, thermal conductivity and electrical conductivity of sintered parts first increased and then decreased with increasing sintering temperature. In our experiments, the tungsten‐40 wt.–% copper sample fabricated by binder jet 3D printing with a printing layer thickness of 50 μm under a sintering temperature of 1500 °C displayed the best properties, in which the relative density, thermal conductivity and electrical conductivity were 97.04 %, 228 W⋅m−1⋅K−1 and 46.5 % IACS, respectively.

Post-printing processing and aging effects on Polyjet materials intended for the fabrication of advanced surgical simulators

Material Jetting (MJ) 3D printing technology is promising for the fabrication of highly realistic surgical simulators, however, the changes in the mechanical properties of MJ materials after post-printing treatments and over time remain quite unknown.In this study, we investigate the effect of different post-printing processes and aging on the mechanical properties of a white opaque and rigid MJ photopolymer, a white flexible MJ photopolymer and on a combination of them. Tensile and Shore hardness tests were conducted on homogeneous 3D-printed specimens: two different post-printing procedures for support removal (dry and water) and further surface treatment (with glycerol solution) were compared. The specimens were tested within 48 h from printing and after aging (30–180 days) in a controlled environment.All groups of specimens treated with different post-printing processes (dry, water, glycerol) exhibited a statistically significant difference in mechanical properties (i.e. elongation at break, elastic modulus, ultimate tensile strength). Particularly, the treatment with glycerol makes the flexible photopolymer more rigid, but then with aging the initial elongation of the material tends to be restored. For the rigid photopolymer, an increase in deformability was observed as a major effect of aging. The hardness tests on the printed specimens highlighted a significant overestimation of the Shore values declared by the manufacturer. The study findings are useful for guiding the material selection and post-printing processing techniques to manufacture realistic and durable models for surgical training.

Printed bioinspired piezoelectric nano-hair for ultrahigh sensitive airflow detection

Micro/nanoscale hairs found in living organisms combine many inspiring properties such as miniaturization, low power consumption, adaptability, and the sensing of signals. Mimicking these excellent biological hairs provided an effective way to develop advanced artificial sensing sensors. Here, a printed bioinspired piezoelectric nano-hair with ultra-high sensitivity was developed for airflow detection. A novel nanoscale electrohydrodynamic jet 3D printing method was developed to fabricate PZT nano-hair with controllability, fast, and inexpensive characteristics. Various PZT nano-hairs down to the scale of 200 nm with high aspect ratio features of 523 were directly printed. Herein, the printed PZT nano-hair exhibited pure perovskite structures, excellent mechanical properties, and a high piezoelectric coefficient. This bioinspired PZT hair sensor demonstrated that the novel printed PZT hair airflow sensor showed ultra-high detection sensitivity to low-speed airflow (0.02 m s−1). This novel nanoprinting strategy and the printed PZT nano-hair indicate the development of functional nanostructures inaccessible by traditional manufacturing methods.

Design of multi-band flexible microstrip antenna based on micro drop jetting

Due to the high compatibility of micro-droplet jetting 3D printing technology within the realm of printed electronics, a flexible and miniaturized multi-band microstrip antenna was designed. The purpose of this is to extend the wireless signal response range of wearable devices and to investigate the feasibility of producing wearable devices with high efficiency. The antenna uses polydimethylsiloxane (PDMS) as the dielectric substrate and nanosilver as the conductive material for the radiating patch, demonstrating remarkable flexibility. The antenna’s structure underwent simulation and analysis through frequency sweeping using ANSYS HFSS simulation software. The outcomes illustrate the antenna operating within three frequency bands at 2.5GHz, 3.5GHz, and 5.8GHz, and the return loss is kept below -18dB for each central frequency. Simultaneously, it displays favorable flexibility. The radiation pattern of the antenna indicates that it has good directivity and no extra side lobes are generated. Ultimately, Antennas were fabricated using microdroplet spraying technology, and the final product’s characteristics and morphology were analyzed. The aforementioned findings demonstrate that micro-droplet jetting technology’s remarkable precision and efficiency render it a viable approach for the processing and production of flexible microstrip antennas.

Adhesive and alloying properties of dual purpose polyfurfuryl alcohol binder for binder jet additive manufacturing of steel

In-situ alloying in steel can be achieved in the binder jet additive manufacturing process by incorporating alloying elements into the binder. However, using binders with nanoparticle suspensions often leads to challenges with particle dispersion uniformity and nozzle clogging. To circumvent these limitations, we investigated the feasibility of using a particle-free binder based on poly(furfuryl alcohol) (PFA) for binder jet 3D printing of steel. The PFA binder serves dual purposes – (i) imparting structural integrity to the as-printed green part and (ii) providing carbon upon pyrolysis to alloy the printed iron parts into steel. The PFA binder was first dispensed layer-by-layer into a low alloy steel powder bed to produce green parts with a storage modulus of 3360 MPa and a compressive strength of up to 9 MPa. Compared to the control, a commercial carbon binder ink, the present particle-free PFA formulation offered better green part rigidity (+18%) and strength (+18.5%) for the same amount of carbon alloying. The green parts were then subjected to debinding and sintering to consolidate the steel powder particles. During vacuum sintering, the PFA was pyrolyzed and left behind a carbon residue which diffused into the steel part to form a hard and strong ferrite-carbide aggregate phase that significantly enhanced the hardness, yield strength and ultimate tensile strength of the sintered steel parts. Furthermore, by varying the amount of this particle-free binder formulation at different locations, components with site-specific microstructures and mechanical responses, confirmed through hardness tests and digital image correlation, were also demonstrated.

Investigation on the spreading behaviour of sand powder used in binder jet 3D printing

Investigation on the spreading behaviour of sand powder used in binder jet 3D printing

Binder Jetting 3D Printing of Binary Cement-Siliceous Sand Mixture.

Three-dimensional printing allows accurate geometries to be obtained across a wide range of applications and it is now also moving into the architecture and construction industry. In the present work, a unique binary mix composed of ordinary Portland cement (OPC) and quick-setting cement (QSC) was combined with silica sand aggregate in different proportions for a customized binder jetting 3D printing (BJ3DP) process. Specimens were printed using the blended dry powders and deionized water to determine the impact of the processing variables on the properties of the realized specimens. The results show that the properties are influenced by the binary mix proportions and the layer thickness. The investigation found significant improvement in mechanical performance on increasing the proportion of OPC and optimal conditions were identified with proportions of 35 wt% OPC and 5 wt% QSC. Notable enhancements were also observed as the layer thickness was reduced.

Promoting sustainability in 3D printed sand casting through adaptive sand mold structures

The use of 3D printed sand molds offers a high degree of flexibility in structural design and satisfying customer requirements. The optimization and adjustment of the structure of sand mold module with the required functionality helps to maximize the application potential of binder jet 3D printing technology. In this study, an adaptive sand mold structure design method was proposed to meet the sustainable requirements of 3D printed sand casting. Firstly, the functional modular and module clustering of the sand mold is carried out and then each module is adaptive structure design, to reduce the carbon emission and cost of the 3D printed casting process. Therefore, taking the small casting furnace cover and medium-sized cast engine block as examples, the life cycle framework of the 3D printed sand casting process is established, and the sustainable advantages of the adaptive structure method are explored through the calculation and analysis of carbon emission and cost models. The results show that the adaptive structure method reduces the carbon emissions of the two castings by 9.2% and 11.9%, respectively, and the cost of two castings by 6.7% and 11.1%, respectively. This approach provides more sustainable design ideas for 3D printed sand casting and 3D printed sand mass production.

High-speed electrolyte jet 3D printing of ultrasmooth and robust Cu microelectrodes

Electrochemical 3D printing technology built on computer numerical control platforms has enabled multi-dimensional and multi-scale manufacturing of various metal materials through layered electrochemical deposition. Compared to thermal 3D printing technology, electrolyte meniscus-confined 3D printing can manufacture Cu microstructures with fewer defects and smoother surfaces. In the meantime, it is still susceptible to unstable liquid–solid-air interfaces, low deposition rates, and limited printing geometry. This work combined jet electrochemical deposition with a portable 3-axis platform to develop a cyclic high-speed electrolyte jet (HSEJ) 3D printer. It offers a faster deposition rate of 53.4 µm/h when printing ultrasmooth Cu microelectrodes with surface average roughness down to 1.1 nm and microhardness of 3.3 GPa which is much higher than the best result of 2.4 GPa obtained by the other ECD methods. It is identified that the fluctuation of cathode current density plays a crucial role in defining the nucleation morphology on the Cu surface, while the cathode current efficiency is a reliable indicator to assess the deposition localization by reflecting the variation of diffusion percentage. HSEJ 3D printing provides a sustainable pathway for the facile recycling of waste cables into high-grade metal microelectronics with controllable surface morphology and 3D dimensions.Graphical

Analysis of gaseous emission and particle number size distributions in metal casting processes with binder jetting moulds

The impact on indoor air quality during metal casting processes using the 3D printing (3DP) binder jetting technique to manufacture moulds is analyzed in this research. This study investigates the particle size distribution and gas concentration during the manufacturing stages of 3DP moulds, with focus on particle deposition in the human respiratory system. The goal is to understand the risks associated with particle and gas emissions in binder jetting 3D printing, and thus improve worker safety. The results indicate that particle emission rates are lowest during printing (0.01 1011particles min−1) but increase during post-processing and melting-pouring phases (3.07 1011 particles min−1). During melting and pouring, the emission of particles was mainly in the range 7.9–71 nm, with values 10 times higher than in the previous phases. The study calculates the deposition of inhaled particles in different parts of the respiratory tract and reveals a 2.39 times higher extrathoracic mass deposition during 3DP mould manufacturing stages compared to melting-pouring stages. Additionally, alveolar mass deposition is higher during melting-pouring stages due to an increase in ultrafine emission rates. The study emphasizes the importance of insulation equipment and workplace ventilation in indoor spaces, particularly during heating processes that generate ultrafine particles through nucleation, so that health risks can be mitigated.

Analysis of Influence of Sand Matrix on Properties of Moulding Compounds Made with Furan Resin Intended for 3D Printing

Binder jetting (BJ) sand printing is a 3D printing process in which a sand mould or sand core is produced from an STL file. A single layer of a sand matrix consisting of one or more grains in height of sand is applied to a worktable, and then a liquid resin or binder is applied to bond the grains together. This process is repeated until the final result matches the CAD model. The sand matrix is the main component of ceramic cores and moulds. The present study aims to demonstrate the influence of the matrix used on the properties of the resulting moulding sand. Three types of sand matrices were selected for the study. The first was a quartz matrix for 3D printing with binder jetting; this is characterised by a sharp geometry that allows for proper layering during printing. Ordinary quartz sand was also used for the study; this type of sand is usually used for the production of sand cores in the hotbox process, among other things. The shape of this sand is irregular. The last matrix to be tested was Cerabeads sand; this was selected because its spherical geometry clearly distinguishes it from the other two matrices. The matrices were analysed for their grain sizes. Scanning electron microscope images were also taken to compare the geometries and chemical compositions of the respective matrices. In presented research utilises a sand matrix for the production of self-curing compounds with furan resin dedicated for binder jetting 3D printing. The moulding masses were produced in a laboratory circulation mixer. The laboratory moulds were produced with wooden core boxes and pre-compacted by vibration. The samples from the matrix for the 3D printing were produced using the binder jetting method. The samples were produced to determine the flexural strength, tensile strength, gas permeability, hot distortion, and apparent density. It was not possible to carry out tests for the Cerabeads sand, as the obtained moulds were too brittle to perform adequate tests. Tests with the other matrices have shown that the shape and size of the matrix affect the apparent density and gas permeability.