3D Printer Nozzle Research Articles

In-situ magnetic alignment model for additive manufacturing of anisotropic bonded magnets

In this work, we report a mathematical framework which predicts the degree of alignment (DoA) in an in-situ aligned additively manufactured 3D printed bonded magnets. A multiphysics model is developed which couples the harmonious interactions of magnetic particles in a viscous flowing polymer under the presence of an external magnetic field. The hydrodynamic fluid-particle interaction is paired with the magnetophoretic force to predict the particle trajectory and distribution during extrusion through a 3D printer nozzle. Succeeding the force balance, a magnetohydrodynamic torque equilibrium analysis is performed to predict the net-orientation of the magnetic particles as a function of the applied field strength, viscous forces, and particle-to-particle interactions (P2P). Experimental validation of the DoA predictions is performed using 65 vol% Nd-Fe-B+Sm-Fe-N in Nylon12 (DoAexp = 0.620 and DoAtheory = 0.686) and 15 vol% Sm-Co in PLA (DoAexp = 0.830 and DoAtheory = 0.863). A parametric analysis is performed to analyze the effect of operating and design parameters like alignment field strength, magnetic loading fraction, extrusion load, and particle size. The model predicts a competing behavior between particle-fluid and particle-particle interactions under the presence of an applied field. The model provides a framework to efficiently predict the DoA in tandem with a functionalized-magnetic 3D printer and allows the user to adjust the operating parameters according to the desired DoA.

Increasing perpendicular alignment in extruded filament by an orifice embedded 3D printing nozzle

ABSTRACT The mixing of fibrous additives in the polymer base is being widely investigated for improving the mechanical properties of printed parts using fused filament fabrication (FFF). In this study, flow visualisation experiments and computational fluid dynamics (CFD) analysis were conducted on the flow channel of a nozzle with an orifice for enhancing the through-layer physical properties of the printed parts. Flow visualisation experiments were conducted on the flow channels of nozzles installed with orifices of various shapes. Using ball-milled carbon fibre in high-viscosity polydimethylsiloxane (PDMS) that imitates filament flow in FFF, the fibre angles were measured for different internal and external locations of the nozzle. The distribution of the fibre angles inside the nozzle was compared with the gradient of the flow field calculated for the same shape by CFD analysis. It was found that the orifice structure inside the nozzle increases the vertical alignment of the fibre. An abrupt increase in the extension rate at the exit of the orifice is considered to be the reason behind the rotation and vertical orientation of fibres inside the nozzle channel. Results presented in this work provide the basis for achieving improved through-plane physical properties of FFF printed parts through fibre alignment.

Effect of the Fourth Industrial Revolution on Road Transport Asset Management Practice in Nigeria

Poor management practices of road transport assets posed a challenge to the sustainable development of the transport system in developing countries like Nigeria. Studies in the past focused mainly on the performance of road construction process. However, few studies have evaluated the effect of the fourth Industrial Revolution (4.0IR) on the road transport assets in developing countries such as Nigeria. The current study aimed at assessing the effect of the 4.0IR towards improving the management practice of road transport assets. Survey instruments were administered to project and facility managers in the Nigerian road construction sector of the economy using a proportionate random sampling technique. Partial least square structural equation modelling was used for data analysis utilising the Warp 7.0 partial least squares-structural equation modelling (PLS-SEM) software algorithm. The software calculates p-values with WarpPLS based on non-parametric algorithms, resampling or stable algorithms and thus does not require that the variables to be normally distributed. The study concluded that the 4.0IR drivers have a moderate effect change on the management practice of road transport assets in Nigeria at the moment. The findings imply that management of road assets in Nigeria would moderately improve due to the 4.0IR technologies resulting in transport, safety and general efficiency and effectiveness of road networks in Nigeria. The study identified the 4.0IR drivers to include robotics, mobility, virtual and augmented reality, Internet of things and cloud computing, machine learning, artificial intelligence, blockchain, three-dimensional (3D) printing drones that are built with an attached 3D printer (the drone hangs a 3D printing nozzle that has fed plastic, concrete mix or other material from a tube connected to the top of the drone's printing path that precisely plotted by software, for a promised printing accuracy of 0.1 mm) and digital engineering. This study emanated from the government reports and past studies in the area of road transport asset management practice which the study investigated the major causes of poor practices and assessed the effect of the 4.0IR on the practice.

Improving Cell Viability and Velocity in μ-Extrusion Bioprinting with a Novel Pre-Incubator Bioprinter and a Standard FDM 3D Printing Nozzle.

Bioprinting is a promising emerging technology. It has been widely studied by the scientific community for the possibility to create transplantable artificial tissues, with minimal risk to the patient. Although the biomaterials and cells to be used are being carefully studied, there is still a long way to go before a bioprinter can easily and quickly produce printings without harmful effects on the cells. In this sense, we have developed a new μ-extrusion bioprinter formed by an Atom Proton 3D printer, an atmospheric enclosure and a new extrusion-head capable to increment usual printing velocity. Hence, this work has two main objectives. First, to experimentally study the accuracy and precision. Secondly, to study the influence of flow rates on cellular viability using this novel μ-extrusion bioprinter in combination with a standard FDM 3D printing nozzle. Our results show an X, Y and Z axis movement accuracy under 17 μm with a precision around 12 μm while the extruder values are under 5 and 7 μm, respectively. Additionally, the cell viability obtained from different volumetric flow tests varies from 70 to 90%. So, the proposed bioprinter and nozzle can control the atmospheric conditions and increase the volumetric flow speeding up the bioprinting process without compromising the cell viability.

3D Printing Temperature Tailors Electrical and Electrochemical Properties through Changing Inner Distribution of Graphite/Polymer.

The rise of 3D printing technology, with fused deposition modeling as one of the simplest and most widely used techniques, has empowered an increasing interest for composite filaments, providing additional functionality to 3D-printed components. For future applications, like electrochemical energy storage, energy conversion, and sensing, the tuning of the electrochemical properties of the filament and its characterization is of eminent importance to improve the performance of 3D-printed devices. In this work, customized conductive graphite/poly(lactic acid) filament with a percentage of graphite filler close to the conductivity percolation limit is fabricated and 3D-printed into electrochemical devices. Detailed scanning electrochemical microscopy investigations demonstrate that 3D-printing temperature has a dramatic effect on the conductivity and electrochemical performance due to a changed conducive filler/polymer distribution. This may allow, e.g., 3D printing of active/inactive parts of the same structure from the same filament when changing the 3D printing nozzle temperature. These tailored properties can have profound influence on the application of these 3D-printed composites, which can lead to a dramatically different functionality of the final electrical, electrochemical, and energy storage device.

3D-Printing Enables Fabrication of Swirl Nozzles for Fast Aerosolization of Water-Based Drugs

Portable inhalers are used for delivering drugs to the lung in the form of aerosols and form the standard treatment for diseases such as Asthma, COPD, and cystic fibrosis. However, for aqueous drug formulations, spray nozzle chips have so far been restricted to cleanroom manufacture due to their small feature sizes. Here we present a spring-actuated 3D-printed swirl nozzle that sprays an aqueous drug solution, matching propellant-containing inhalers in aerosolization time. The use of two-photon polymerization enables the small nozzle feature size of 100 $\mu \text{m}$ and device print times of only 4 min, making serial mass-fabrication a viable option. Our 35 bar spring-operated swirl nozzle prototype achieves mean volumetric particle sizes of 12.5 ${\mu }\text{m}$ on doses of 100 ${\mu }\text{l}$ , aerosolized in 270 ms, as fast as a propellant-driven inhaler. [2021-0002]

A Study on the Effect of FFF 3D Printer Nozzle Size and Layer Height on Radiation ShieldFabrication

A Study on the Effect of FFF 3D Printer Nozzle Size and Layer Height on Radiation ShieldFabrication

3D Printing of Plant-Derived Compounds and a Proposed Nozzle Design for the More Effective 3D FDM Printing

Additive manufacturing technology has been developed in the manufacturing industry; however, limited choice of materials and low printing speeds in large-scale production make 3D printing challenging in the industry. Wood and cellulose-based materials have recently drawn a lot of attention for use as 3D printing materials due to their unique properties such as environmental friendliness, cost-effectiveness and abundancy. However, because these compounds are derived from various natural sources, their different particle sizes can result in low 3D printing quality. The objective of this study is to resolve the mentioned deficiencies in the packaging industry by designing a novel 3D printer nozzle based on the material extrusion method (FDM technique), which provides higher printing speed and enhanced quality for wood and cellulose-based materials. The packaging industry can significantly benefit from 3D printing technology for cellulose-based materials by producing high-quality recyclable economical packaging on a large scale according to the clients’ demand. The proposed nozzle design enables selecting different geometrical cross-sections of the nozzle dies and any number of extrusion points along the nozzle die simultaneously during the 3D printing process. These capabilities lead to advanced performance and improved speed of 3D printing in large scale manufacturing. The proposed nozzle design provides a novel technique for 3D printing of plant-derived compounds with remarkable advantages such as providing selective variable extrusion and multiple nozzle dies. Compared to other existing 3D printing techniques, the proposed nozzle abilities make it a promising option with higher speed and better functionality for the packaging industry.

Structural Design of 3D Printer Nozzle with Superior Heat Dissipation Characteristics for Deposition of Materials with High Melting Point

Structural Design of 3D Printer Nozzle with Superior Heat Dissipation Characteristics for Deposition of Materials with High Melting Point

Microfluidic droplet generation based on non-embedded co-flow-focusing using 3D printed nozzle

Most commercial microfluidic droplet generators rely on the planar flow-focusing configuration implemented in polymer or glass chips. The planar geometry, however, suffers from many limitations and drawbacks, such as the need of specific coatings or the use of dedicated surfactants, depending on the fluids in play. On the contrary, and thanks to their axisymmetric geometry, glass capillary-based droplet generators are a priori not fluid-dependent. Nevertheless, they have never reached the market because their assembly requires fastidious and not scalable fabrication techniques. Here we present a new device, called Raydrop, based on the alignment of two capillaries immersed in a pressurized chamber containing the continuous phase. The dispersed phase exits one of the capillaries through a 3D-printed nozzle placed in front of the extraction capillary for collecting the droplets. This non-embedded implementation of an axisymmetric flow-focusing is referred to non-embedded co-flow-focusing configuration. Experimental results demonstrate the universality of the device in terms of the variety of fluids that can be emulsified, as well as the range of droplet radii that can be obtained, without neither the need of surfactant nor coating. Additionally, numerical computations of the Navier-Stokes equations based on the quasi-steadiness assumption allow to provide an explanation to the underlying mechanism behind the drop formation and the mechanism of the dripping to jetting transition. Excellent predictions were also obtained for the droplet radius, as well as for the dripping-jetting transition, when varying the geometrical and fluid parameters, showing the ability of this configuration to enventually enhance the dripping regime. The monodispersity ensured by the dripping regime, the robustness of the fabrication technique, the optimization capabilities from the numerical modelling and the universality of the configuration confer to the Raydrop technology a very high potential in the race towards high-throughput droplet generation processes.

Singlemoded THz guidance in bendable TOPAS suspended-core fiber directly drawn from a 3D printer

Terahertz (THz) technology has witnessed a significant growth in a wide range of applications, including spectroscopy, bio-medical sensing, astronomical and space detection, THz tomography, and non-invasive imaging. Current THz microstructured fibers show a complex fabrication process and their flexibility is severely restricted by the relatively large cross-sections, which turn them into rigid rods. In this paper, we demonstrate a simple and novel method to fabricate low-cost THz microstructured fibers. A cyclic olefin copolymer (TOPAS) suspended-core fiber guiding in the THz is extruded from a structured 3D printer nozzle and directly drawn in a single step process. Spectrograms of broadband THz pulses propagated through different lengths of fiber clearly indicate guidance in the fiber core. Cladding mode stripping allow for the identification of the single mode in the spectrograms and the determination of the average propagation loss (~ 0.11 dB/mm) in the 0.5–1 THz frequency range. This work points towards single step manufacturing of microstructured fibers using a wide variety of materials and geometries using a 3D printer platform.

Rapid Synthesis of Porous Graphene Microspheres through a Three-Dimensionally Printed Inkjet Nozzle for Selective Pollutant Removal from Water

Graphene microspheres are fabricated through a 3D-printed inkjet nozzle based on the gas–liquid microfluidic method. This method realizes rapid and controllable fabrication of uniform graphene microspheres with up to 800 μL min–1 (ca. 1 L d–1) of yields, which is 2 orders of magnitude higher than those of the conventional microfluidic method. The diameter of the graphene microspheres could be flexibly controlled from 0.5 to 3.5 mm by adjusting the gas pressure. The porous graphene microspheres show great dye decoloration performance. The maximum adsorption capacity of methylene blue is 596 mg/g, which is the highest adsorption capacity among that of the reduced graphene-oxide absorbents. A performance improvement of 21% is obtained by applying sodium alginate into graphene as a curing agent. The adsorption behavior follows a Langmuir isotherm and pseudo-second-order kinetic model. Besides, the graphene microspheres exhibit great selective adsorption and could separate cationic dye methylene blue (MB) and anionic dye methyl orange (MO).

Microfluidics as a Platform for the Analysis of 3D Printing Problems.

Fused Filament Fabrication is an extrusion deposition technique in which a thermoplastic filament is melted, pushed through a nozzle and deposited to build, layer-by-layer, custom 3D geometries. Despite being one of the most widely used techniques in 3D printing, there are still some challenges to be addressed. One of them is the accurate control of the extrusion flow. It has been shown that this is affected by a reflux upstream the nozzle. Numerical models have been proposed for the explanation of this back-flow. However, it is not possible to have optical access to the melting chamber in order to confirm the actual behavior of this annular meniscus. Thus, microfluidics seems to be an excellent platform to tackle this fluid flow problem. In this work, a microfluidic device mimicking the 3D printing nozzle was developed, to study the complex fluid-flow behavior inside it. The principal aim was to investigate the presence of the mentioned back-flow upstream the nozzle contraction. As the microfluidic chip was fabricated by means of soft-lithography, the use of polymer melts was restricted due to technical issues. Thus, the working fluids consisted of two aqueous polymer solutions that allowed replicating the printing flow conditions in terms of Elasticity number and to develop a – flow map. The results demonstrate that the presence of upstream vortices, due to the elasticity of the fluid, is responsible for the back-flow problem.

Experimental investigation of microbubble generation in the venturi nozzle

We studied the effect of varying the entry and exit angles of Venturi nozzles on the formation of microbubbles in Venturi nozzle-type microbubble generators. We 3D-printed nozzles with five entry angles (15, 22, 30, 38 and 45°) and five exit angles (15, 22, 30, 38 and 45°). For the visualization experiment, we inserted the nozzles into a cover case made of aluminum and transparent acrylic. We measured the pressure drop and the air flow rate with respect to the entry and exit angles, determined the diameters of the bubbles using a digital camera, and analyzed bubble breakage by observing the behavior of the bubbles using a high-speed camera. We confirmed that the exit angle (not the entry angle) is dependent on the pressure drop and found that the air flow rate did not vary linearly with the fluid flow rate, as expected according to Bernoulli's theorem. Instead, it tended to remain constant or decrease as the fluid flow rate increased due to the abnormal flow. The sizes of the bubbles decreased as the exit angle increased, except in cases where the outlet angle was greater than 30° at high flow rates (260–300 LPM). We observed a change in bubble size with respect to exit angle. According to our visualization, the bubbles were broken by the flow separation at the beginning of the divergence at the exit.

Collection of airborne ultrafine cellulose nanocrystals by impinger with an efficiency mimicking deposition in the human respiratory system

As cellulose nanocrystals (CNCs) are increasing in production, establishing safe workplace practices in industry will be paramount to their continued use and growth. Particles other than CNCs with similar high aspect ratios have exhibited toxicity on inhalation. Safeguards are needed to monitor concentrations of CNCs in air in industrial and laboratory settings to protect workers. However, because of their size, morphology, and chemical makeup, CNCs are difficult to characterize and differentiate from other dust and cellulose products. This work is focused on developing an effective method of characterizing the concentration of airborne ultrafine CNCs that may deposit in the respiratory tract. CNCs were tagged with rhodamine b (RhB-CNCs) for improved visualization and characterized using UV-vis spectroscopy (UV-vis), transmission electron microscopy (TEM), and dynamic light scattering (DLS), then aerosolized and collected via a novel method using plastic impingers. Concentration of RhB-CNCs was measured using UV-vis and scanning mobility particle sizer (SMPS). The plastic impinger with 3D-printed nozzle collected airborne CNCs at an efficiency that improves upon commercially available impingers for relevant particle sizes.

In-line rheological monitoring of fused deposition modeling

An in-line rheometer has been incorporated into a fused deposition modeling printer for the first time by designing a modified nozzle with a custom pressure transducer and a thermocouple for measuring the processed melt temperature. Additionally, volumetric flow rates and shear rates were monitored by counting the stepper motor pulses as well as the pulses from a custom filament encoder to account for filament slippage and skipped motor steps. The incorporation of the sensors and the design and development of the in-line rheometer are described; and pressures, temperatures, and viscosities within the 3D printing nozzle are presented. The in-line rheometer was validated against traditional, off-line rotational rheology and capillary rheology measurements by analyzing two polymeric materials: polycarbonate and high-impact polystyrene. A variety of rheological corrections were considered for the in-line rheometer, including entrance effects, non-Newtonian corrections, shear heating, pressure effects, and temperature fluctuations/inaccuracies. Excellent agreement was obtained between the in-line and off-line rheometers after applying the most critical corrections, which were found to be entrance effects, non-Newtonian corrections, and temperature inaccuracies. After applying the appropriate corrections, the in-line rheometer provides an accurate viscosity measurement that can be used for real-time monitoring and process control.

Novel method for manufacturing optical fiber: extrusion and drawing of microstructured polymer optical fibers from a 3D printer.

Microstructured polymer optical fibers (MPOFs) have long attracted great interest due to their wide range of applications in biological and chemical sensing. In this manuscript, we demonstrate a novel technique of manufacturing MPOF via a single-step procedure by means of a 3D printer. A suspended-core polymer optical fiber has been extruded and directly drawn from a micro-structured 3D printer nozzle by using an acrylonitrile butadiene styrene (ABS) polymer. Near-field imaging at the fiber facet performed at the wavelength λ~1550 nm clearly indicates guidance in the fiber core. The propagation loss has been experimentally demonstrated to be better than α = 1.1 dB/cm. This work points toward direct MPOFs manufacturing of varieties of materials and structures of optical fibers from 3D printers using a single manufacturing step.

A modular, 3D-printed helium-filled soap bubble generator for large-scale volumetric flow measurements

A modular helium-filled soap bubble (HFSB) generator consisting of 3D-printed nozzles and developed for use in a wind tunnel is characterized. A multi-syringe pump accurately feeds bubble film solution (BFS) to each nozzle while air and helium flow rates are regulated using mass flow controllers. The modular design of the system allows for the customization of the HFSB streamtube to each unique experiment. Modules can be arranged in various configurations to increase seeding density and manipulate the size of the streamtube. Shadowgraphy, particle image velocimetry, particle tracking velocimetry, and laser-based imaging are used to characterize the particle sizes, tracing fidelity, production rates, and seeding density of a system consisting of two modules (8 nozzles in total). It is shown that nozzle performance, particle time response, and production rates can be controlled by varying the flow rates of air, helium, and BFS into the system, respectively. The optimal operating case resulted in the production of approximately 70,000 bubbles/s from each nozzle. The bubbles were neutrally buoyant on average and had a mean diameter of 0.46 mm. The two modules resulted in a streamtube with an effective cross-section of 15 × 15 cm2. The streamtube was produced continuously, resulting in a seeding density of 1.6 bubbles/cm3 at free stream velocity of 10.3 m/s.

Analysis of Mechanical Properties of Polylactic Acid Using a New 3D Printer Nozzle

Additive manufacturing, also known as three-dimensional (3D) printing, is the process of developing 3D products in a layer-by-layer manner using filament as a material feedstock to create a solid structure. Owing to its unique properties and advantages, which include biodegradability and printing speed, polylactic acid is one of the most common 3D printing extrusion materials. While a considerable attention has been paid to the manipulation of process parameters in order to achieve desired finished product quality, to date less research has been performed on improving the hardware systems of low-cost 3D printers. This study focuses on fabricating the 3D printer nozzle parts, with an emphasis on die angle, nozzle diameter, liquefier design, and insulator composition. Modifying the properties of these components from the conventional nozzle, it is possible to optimize the stability and accuracy of the extrusion process, leading to better-quality printed products. To demonstrate the capability of the new nozzle, its tensile and compressive strengths were compared to those of a conventional nozzle. The obtained results proved that the proposed augmentations to the nozzle system lead to finished products with improved mechanical properties.

Penetration of cement pastes into sand packings during 3D printing: analytical and experimental study

3D printing processes of concrete and cement based materials could bring architectural and structural innovation in construction industry. Additive manufacturing and digital fabrication methods in civil engineering have recently been developed at laboratory scale. Among the 3D printing processes that could bring new perspectives in innovative and designed architectural elements, one of the most interesting is called the selective paste intrusion method. The component is built layer by layer by selectively applying cement paste on an aggregate packing using a 3D printer nozzle and a subsequent penetration of the paste into the aggregate layer. The implementability of the selective paste intrusion method requires the prediction of the flow of a yield stress fluid through a porous media. The rheological behaviour of the cement paste must be adapted for its penetration through the porous network of the aggregate particle packing. An adequate penetration depth of the cement paste produces homogeneous materials that are capable of sustaining a high mechanical stress. We show in this paper that the compressive strength of component made by such a technique is directly linked to the penetration depth of the cement paste into the aggregate layer; consequently, this paper aims at predicting the penetration depth of cement pastes into sand layers. A theoretical framework has been developed to propose an evaluation of penetration depth as a function of the average sand grain diameter and the yield stress of the cement paste, which is experimentally validated with specific penetration measurements. Finally, we stress that the prediction of penetration with an analytical model is an effective technique to ensure building homogeneous cement based materials with the 3D printing selective binding method.