Binder jetting, a commercial additive manufacturing process that selectively deposits a liquid binder onto a powder bed, can become a viable method to additively manufacture ceramics. However, the ...effects of process parameters/inputs on printing outputs (e.g. part density and geometric resolution) have not been investigated and no methodical approach exists for the process development of new materials. In this work, a parametric study consisting of 18 experiments with unique process input combinations explores the influence of seven process inputs on the relative densities of as-printed (green) alumina (Al2O3) parts. Sensitivity analyses compare the influence of each input on green densities. Multivariable linear and Gaussian process regressions provide models for predicting green densities as a function of binder jetting process inputs. The parametric study reveals that two process inputs, namely recoat speed and oscillator speed, significantly influence green densities. The multivariable linear and Gaussian process regression models indicate that the green densities of alumina builds can be increased by decreasing the recoat speed and increasing the oscillator speed. The Gaussian process regression model further suggests that the green densities have nonlinear dependence on the rest of the process parameters. Separate prints were performed at process input combinations different than those of the parametric study to validate the green density models. The models produced can assist operators in selecting process inputs that will result in a desired green density, allowing for the control of porosity in printed parts with a high degree of accuracy. The methodology reported in this study can be leveraged for other powder systems and machines to predict and control the porosity of binder jetted parts for applications such as filters, bearings, electronics, and medical implants.
Purpose
Material-jetting (MJ) three-dimensional (3D) printing processes are competitive due to their printing resolution and printing speed. Driving waveform design of piezoelectric printhead in MJ ...would affect droplet formation and performance, but there are very limited studies on it besides patents and know-hows by commercial manufacturers. Therefore, in this research, the waveform design process to efficiently attain suitable parameters for a multi-nozzle piezoelectric printhead was studied. Therefore, this research aims to study the waveform design process to efficiently attain suitable parameters for a multi-nozzle piezoelectric printhead.
Design/methodology/approach
Ricoh’s Gen4L printhead was adopted. A high-speed camera captured pictures of jetted droplets and droplet velocity was calculated. The waveforms included single-, double- and triple-pulse trapezoidal patterns. The effects of parameters were investigated and the suitable ones were determined based on the avoidance of satellite drops and preference of higher droplet velocity.
Findings
In a single-pulse waveform, an increase of fill time (Tf) decreased the droplet velocity. The maximum velocity happened at the same pulse width, the sum of fill time and hold time (Tf + Th). In double- and triple-pulse, a voltage difference (Vd) above zero in the holding stage was adopted except the last pulse to avoid satellite drops. Suitable parameters for the selected resin were obtained and the time-saving design process was established.
Research limitations/implications
Based on the effects of parameters and observed data trends, suggested procedures to determine suitable parameters were proposed with fewer experiments.
Practical implications
This study has verified the feasibility of suggested design procedures on another resin. The required number of trials was reduced significantly.
Originality/value
This research investigated the process of driving waveform design for the multi-nozzle piezoelectric printhead. The suggested procedures of finding suitable waveform parameters can reduce experimental trials and will be applicable to other MJ 3D printers when new materials are introduced.
Digital inkjet printing technology has great significance in textiles. In this paper, influences of two additives on the dye aggregation and jetting performance of reactive dye solutions are ...investigated, and the mechanism is analyzed. We explored the physical properties and jetting performance of reactive dye solutions with 2-pyrrolidone (PY) or N-methyl pyrrolidone (NMP) by testing UV–visible absorption spectrum, rheological properties, surface tension, and observing the droplet formation. The results showed that PY and NMP could inhibit the dye aggregation. Moreover, two lactam compounds decreased the surface tension and increased the viscosity of dye solutions by the interaction between lactam compounds and reactive dye. PY and NMP could reduce the generation of satellite droplets of dye solutions. In addition, 5% PY/Red 218 and 5% NMP/Red 218 solutions produced better color images on cotton fabrics.
Display omitted
•Lactam compounds are used as cosolvents in reactive dye solution.•Interaction between lactam compounds and reactive dye affects the jetting performance of dye solutions.•Two lactam compounds improve the formation of droplets in reactive dye solution.•Two lactam compounds improve color images of dye solutions on cotton fabrics.
This study details property measurements from 3–3 BaTiO3-epoxy composite discs, fabricated using binder jet printing and post-sinter epoxy infiltration. Binder jet printing is a highly scalable ...additive manufacturing technique that has the potential to produce transducers with non-conventional geometries and without expensive tooling. Piezoelectric ceramic-epoxy composites are useful for certain applications, such as biomedical imaging and underwater communications, but ordinarily require difficult fabrication processes. Density, dielectric, and piezoelectric property measurements from discs sintered at temperatures between 1200—1400 °C are presented. Measured samples had porosity as low as φ=32.4%, while having a piezoelectric coefficient, electromechanical coupling coefficient, and permittivity as high as d33=110 pC/N, kp=0.274, and ε33T/ε0=411, respectively. Findings show a limitation to increasing sintering temperature to decrease porosity, and suggest a trade-off when selecting a sintering temperature between minimizing φ and maximizing kp. Measurements from the printed discs are compared to measurements from a disc fabricated using a traditional uniaxial pressing method.
•Jet was observed on the the pendant droplet when liquid stream flows out micro-orifice.•The stream upper boundary moves due to the wetting/dewetting around the orifices.•The hysteresis between the ...D–J/J–D transitions is related to the orifice wetting.•Adding and removing the droplet (no pressure changing) achieves the transition.
The liquid stream from an orifice typically undergoes a transition process from dripping to jetting under increased pressure. The dripping–jetting (D–J) transition performance from a thin-walled tube or an orifice with a wide diameter has been well studied, where the triple contact line of the stream is pinned on the edge of the orifice and the flow behaviors are analyzed accordingly with a precondition of the fixed contact line. The D–J transition of the liquid stream from plate-type micro-orifices was investigated in our study of droplet generation for extreme ultraviolet source and wafer cleaning. The triple contact line of the stream keeps moving as pressure changes as a result of the liquid wetting and dewetting around the micro-orifice. The transition from dripping to jetting involves three processes: wetting to generate pendant droplet and dripping, jetting from pendant droplet, and pendant droplet dewetting to form jetting directly. The aforementioned performance is different from boundary-pinned conditions. To reveal the transition characteristic, critical pressure causing the D–J transition under different wetting conditions was determined. The process of wetting to generate pendant droplet and dripping, and the effects of the contact angle and the pressure difference were formulated. Analysis of the mechanism causing jetting from the pendant droplet was implemented by combining a model formulating the jet ejecting outside the droplet and numerical simulation of the stream inside the pendant droplet. Finally, the normalized model was built to illustrate the critical pressure of D–J transition concerning the triple contact line diameter.
Growing knowledge of the key molecular components involved in biological processes such as endocytosis, exocytosis, and motility has enabled direct testing of proposed mechanistic models by ...reconstitution. However, current techniques for building increasingly complex cellular structures and functions from purified components are limited in their ability to create conditions that emulate the physical and biochemical constraints of real cells. Here we present an integrated method for forming giant unilamellar vesicles with simultaneous control over (i) lipid composition and asymmetry, (ii) oriented membrane protein incorporation, and (iii) internal contents. As an application of this method, we constructed a synthetic system in which membrane proteins were delivered to the outside of giant vesicles, mimicking aspects of exocytosis. Using confocal fluorescence microscopy, we visualized small encapsulated vesicles docking and mixing membrane components with the giant vesicle membrane, resulting in exposure of previously encapsulated membrane proteins to the external environment. This method for creating giant vesicles can be used to test models of biological processes that depend on confined volume and complex membrane composition, and it may be useful in constructing functional systems for therapeutic and biomaterials applications.
Binder jet additive manufacturing (BJAM) is capable of fabricating complex three-dimensional components from a variety of material classes. Understanding the fundamentals of BJAM, including spreading ...of thin layers of powder, powder-binder interactions, and post-processing is critical to develop robust process parameters for BJAM. Toward meeting these needs, this work presents the design, fabrication, and qualification of a testbed for modular, mechanized, BJAM. The testbed seeks to replicate the operating conditions of commercial AM equipment and features fully programmable motion control including powder spreading using a precision roller mechanism, powder supply via a vibrating hopper, and gantry positioning of an inkjet printhead. The inkjet deposition system allows for the use of variable nozzle diameters, the exploration of novel binder compositions, and full control of jetting parameters. Validation of the accuracy and repeatability of the machine and its subsystems, as well as the fabrication of exemplary stainless steel components, are described. The precision engineered testbed can therefore enable the study of the BJAM process, exploration of novel binder compositions, and processing of custom powders to further scientific research and industrial applicability of BJAM.
Graphical Abstract
Purpose
Binder jetting is a promising route to produce complex copper components for electronic/thermal applications. This paper aims to lay a framework for determining the effects of sintering ...parameters on the final microstructure of copper parts fabricated through binder jetting.
Design/methodology/approach
The knowledge gained from well-established powder metallurgy processes was leveraged to study the densification behaviour of a fine high-purity copper powder (D50 of 3.4 µm) processed via binder jetting, by performing dilatometry and microstructural characterization. The effects of sintering parameters on densification of samples obtained with a commercial water-based binder were also explored.
Findings
Sintering started at lower temperature in cold-pressed (∼680 °C) than in binder jetted parts (∼900 °C), because the strain energy introduced by powder compression reduces the sintering activation energy. Vacuum sintering promoted pore closure, resulting in greater and more uniform densification than sintering in argon, as argon pressure stabilizes the residual porosity. About 6.9% residual porosity was obtained with air sintering in the presence of graphite, promoting solid-state diffusion by copper oxide reduction.
Originality/value
This paper reports the first systematic characterization of the thermal events occurring during solid-state sintering of high-purity copper under different atmospheres. The results can be used to optimize the sintering parameters for the manufacturing of complex copper components through binder jetting.
A novel binder jetting process using a mixture of sodium silicate powders and water-based solvent as an inorganic binder system and the corresponding posttreatment process were developed to resolve a ...contradiction of increased strength with reduced gas volume of sand molds fabricated by traditional binder jetting processes using organic binder. Optimized processing parameters of 50 % binder saturation, 10 wt% sodium silicate powder addition, 0.2 mm layer thickness, 50 vol% infiltration concentration of alcohol – water solution, 5 min infiltration time, and 250 °C baking temperature buried in glass beads for 1 h were determined by the systematically investigation of printing process. The produced sand mold achieved an excellent performance with a tensile strength of 4.5 MPa and a maximum gas volume of 8.1 L/kg. A casting experiment was carried out to verify the performance of sand mold, the results showed that the casting fabricated using the sand mold prepared by the process studied in this paper has a better surface quality and fewer subcutaneous blowholes in comparison to the traditional process, indicating its excellent industrial application prospects.
Larger well diameters allow higher groundwater ion rates. But particularly for the construction of wells at greater depth, it may be more cost‐efficient to only expand the borehole in the target ...aquifer. However, current drilling techniques for unconsolidated formations are limited by their expansion factors (<2) and diameters (<1000 mm). Therefore, we developed a new technique aiming to expand borehole diameters at depth in a controlled manner using a low‐pressure water jet perpendicular to the drilling direction and extendable by means of a pivoting arm. During a first field test, the borehole diameter was expanded 2.6‐fold from 600 to 1570 mm at a depth of 53.5 to 68 m and equipped with a well screen to create an expanded diameter gravel well (EDGW). In keeping with the larger diameter, the volume flux per m screen length was two times higher than conventional 860 mm diameter wells at the site in the subsequent 3 year production period. Although borehole clogging was slower on a volumetric basis and similar when normalized to borehole wall area, rehabilitation of particle clogging at the borehole wall was more challenging due to the thickness of the gravel pack. While jetting the entire borehole wall before backfilling holds promise to remove filter cake and thus limit particle clogging, we found that a second borehole (expanded 4.1‐fold to 2460 mm) collapsed during jetting. Overall, the EDGW technique has potential to make the use of deeper unconsolidated aquifers economically (more) feasible, although further understanding of the borehole stability and rehabilitation is required to assess its wider applicability.
Article impact statement: A novel drilling technique was developed and tested to expand the diameter of wells at depth during construction in unconsolidated aquifers.
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