Print Head Research Articles

3D printing via ambient reactive extrusion

Additive Manufacturing (AM) has the potential to offer many benefits over traditional manufacturing methods in the fabrication of complex parts with advantages such as low weight, complex geometry, and embedded functionality. In practice, today’s AM technologies are limited by their slow speed and highly directional properties. To address both issues, we have developed a reactive mixture deposition approach that can enable 3D printing of polymer materials at over 100X the volumetric deposition rate, enabled by a greater than 10X reduction in print head mass compared to existing large-scale thermoplastic deposition methods, with material chemistries that can be tuned for specific properties. Additionally, the reaction kinetics and transient rheological properties are specifically designed for the target deposition rates, enabling the synchronized development of increasing shear modulus and extensive cross linking across the printed layers. This ambient cure eliminates the internal stresses and bulk distortions that typically hamper AM of large parts, and yields a printed part with inter-layer covalent bonds that significantly improve the strength of the part along the build direction. The fast cure kinetics combined with the fine-tuned viscoelastic properties of the mixture enable rapid vertical builds that are not possible using other approaches. Through rheological characterization of mixtures that were capable of printing in this process as well as materials that have sufficient structural integrity for layer-on-layer printing, a “printability” rheological phase diagram has been developed, and is presented here. We envision this approach implemented as a deployable manufacturing system, where manufacturing is done on-site using the efficiently-shipped polymer, locally-sourced fillers, and a small, deployable print system. Unlike existing additive manufacturing approaches which require larger and slower print systems and complex thermal management strategies as scale increases, liquid reactive polymers decouple performance and print speed from the scale of the part, enabling a new class of cost-effective, fuel-efficient additive manufacturing.

Applications of Open Source GMAW-Based Metal 3-D Printing

The metal 3-D printing market is currently dominated by high-end applications, which make it inaccessible for small and medium enterprises, fab labs, and individual makers who are interested in the ability to prototype and additively manufacture final products in metal. Recent progress led to low-cost open-source metal 3-D printers using a gas metal arc welding (GMAW)-based print head. This reduced the cost of metal 3-D printers into the range of desktop prosumer polymer 3-D printers. Consequent research established good material properties of metal 3-D printed parts with readily-available weld filler wire, reusable substrates, thermal and stress properties, toolpath planning, bead-width control, mechanical properties, and support for overhangs. These previous works showed that GMAW-based metal 3-D printing has a good adhesion between layers and is not porous inside the printed parts, but they did not proceed far enough to demonstrate applications. In this study, the utility of the GMAW approach to 3-D printing is investigated using a low-cost open-source metal 3-D printer and a converted Computer Numerical Control router machine to make useful parts over a range of applications including: fixing an existing part by adding a 3-D metal feature, creating a product using the substrate as part of the component, 3-D printing in high resolution of useful objects, near net objects, and making an integrated product using a combination of steel and polymer 3-D printing. The results show that GMAW-based 3-D printing is capable of distributed manufacturing of useful products for a wide variety of applications for sustainable development.

User interface tool for a novel plasma-assisted bio-additive extrusion system

PurposeThis paper aims to describe the control software of a novel manufacturing system called plasma-assisted bio-extrusion system (PABS), designed to produce complex multi-material and functionally graded scaffolds for tissue engineering applications. This fabrication system combines multiple pressure-assisted and screw-assisted printing heads and plasma jets. Control software allows the users to create single or multi-material constructs with uniform pore size or pore size gradients by changing the operation parameters, such as geometric parameters, lay-down pattern, filament distance, feed rate and layer thickness, and to produce functional graded scaffolds with different layer-by-layer coating/surface modification strategies by using the plasma modification system.Design/methodology/approachMATLAB GUI is used to develop the software, including the design of the user interface and the implementation of all mathematical programing for both multi-extrusion and plasma modification systems.FindingsBased on the user definition, G programing codes are generated, enabling full integration and synchronization with the hardware of PABS. Single, multi-material and functionally graded scaffolds can be obtained by manipulating different materials, scaffold designs and processing parameters. The software is easy to use, allowing the efficient control of the PABS even for the fabrication of complex scaffolds.Originality/valueThis paper introduces a novel additive manufacturing system for tissue engineering applications describing in detail the software developed to control the system. This new fabrication system represents a step forward regarding the current state-of-the-art technology in the field of biomanufacturing, enabling the design and fabrication of more effective scaffolds matching the mechanical and surface characteristics of the surrounding tissue and enabling the incorporation of high number of cells uniformly distributed and the introduction of multiple cell types with positional specificity.

Microfluidics: A New Layer of Control for Extrusion-Based 3D Printing.

Advances in 3D printing have enabled the use of this technology in a growing number of fields, and have started to spark the interest of biologists. Having the particularity of being cell friendly and allowing multimaterial deposition, extrusion-based 3D printing has been shown to be the method of choice for bioprinting. However as biologically relevant constructs often need to be of high resolution and high complexity, new methods are needed, to provide an improved level of control on the deposited biomaterials. In this paper, we demonstrate how microfluidics can be used to add functions to extrusion 3D printers, which widens their field of application. Micromixers can be added to print heads to perform the last-second mixing of multiple components just before resin dispensing, which can be used for the deposition of new polymeric or composite materials, as well as for bioprinting new materials with tailored properties. The integration of micro-concentrators in the print heads allows a significant increase in cell concentration in bioprinting. The addition of rapid microfluidic switching as well as resolution increase through flow focusing are also demonstrated. Those elementary implementations of microfluidic functions for 3D printing pave the way for more complex applications enabling new prospects in 3D printing.

Characterisation and application of pigmented UV-curable inkjet inks

PurposeThe purpose of this paper is to prepare ultra-violet (UV)-curable inkjet inks for textile printing application. The influence of both type and component ratio of monomer/oligomer on the quality of the desired viscosity range is studied. Moreover, the effect of pigment/resin ratio on the rheological behaviour of the ink has been studied.Design/methodology/approachAqueous dispersions of nanoscale organic pigments were prepared through ball milling and ultrasonication. The dispersed pigments were encapsulated into UV-curable resin via miniemulsion technique, using different types and component ratios of monomers and oligomers.FindingsIt was found that the monomer/oligomer ratio of 2:3 and the pigment/resin ratio of 2:1 gave the most stable miniemulsion dispersions and provided the most suitable rheological range for inkjet printing inks.Research limitations/implicationsAs the rheology of the ink is optimised, most of the problems associated with the jetting process could be avoided.Practical implicationsThis method of using UV-curable encapsulated inks eliminates the usage of binders, which are the principal factor for nozzle clogging of the print head. In addition, binders are responsible for the coarse handle of the printed textiles.Social implicationsThe UV-curable inks were viewed as a green technology by the US Environmental Protection Agency.Originality/valueThis method is simple and fast and requires low cost. In addition, it could find numerous applications in surface coating.

Building a Modified Replicating Rapid-Prototyping Printer (RepRap) for Extrusion BioPlotting of Cardiomyocytes atop Planar Microelectrode Arrays (MEAs)

Building a Modified Replicating Rapid-Prototyping Printer (RepRap) for Extrusion BioPlotting of Cardiomyocytes atop Planar Microelectrode Arrays (MEAs)

Effect of surface slope and build orientation on surface finish and dimensional accuracy in material jetting processes

This work seeks to elucidate the effect of surface slope and build orientation upon the surface finish and dimensional accuracy of specimens fabricated by material jetting processes. Specimens with a flat area and four feature designs (i.e., spherical and prismatic hole and protrusions) were printed in two orientations (i.e., along (XY) and across (YX) the print head direction) and two surface slopes (i.e., horizontal (0∘) and 45∘) and scanned with a white-light profilometer to quantify the surface texture, areal, and material ratio parameters for dimensional accuracy and areal fidelity. The results indicate that surface slope and build orientation appear to have a greater influence on the recessed features compared to the protruded ones. The height and volumetric functional surface parameters are significant and show better surface finish for the 0∘ surface slope compared to 45∘. Also, prismatic and recessed features might benefit from printing on a 45∘ sloped surface while the design fidelity of cross-sections in holes and protrusions greatly vary depending on the specimen slope. The contributions of this work include illustrating the potential for increased production, resolution and fidelity capabilities if 3D printing equipment could incorporate tilting print trays, adaptable print orientation, and local angles, among others.

Electrospinning writing with molten poly (ε-caprolactone) from different directions – Examining the effects of gravity

This work investigates the effect of gravity during melt electrospinning writing (MEW) and explores the feasibility of developing MEW devices with lateral and upside down print head configurations. Average fibre diameters of printed constructs using different printing directions and their variability reveal particular differences. These give an insight into the effect of gravity, which was observed to affect the Taylor cone, yet interestingly not the fibre jet. Additionally, stable processing conditions were studied and showed that it is possible to reproducibly print from all directions using MEW.

Screw extrusion-based additive manufacturing of PEEK

Polyether-ether-ketone (PEEK) has high mechanical strength, thermal performance, and biocompatibility, and is widely used in biomedical and chemical engineering applications. However, to date there are no guidelines for the building of a 3D printer for highly viscous materials, e.g., PEEK. In this paper, a screw extrusion method was developed to overcome the existing problems of the filament-feeding method. Excellent flow stability (<3% variation) and high printing speed (up to 370mm/s) for PEEK printing were achieved. Highly reproducible mechanical tests of the printing products were demonstrated with 96% of the bulk material strength for the first time. Furthermore, an exchangeable printing head was built to cover both line- and plane-printing needs to widen its applications and improve printing surface quality (up to 0.945nm in Ra). All printed material had a more brittle character in comparison with the bulk material and the post annealing process was found to have no significant effect on the mechanical strength. Additionally, porous artificial intervertebral cages with controllable size and distribution were manufactured to demonstrate potential applications.

Printability analysis in additive manufacturing

In recent years Additive Manufacturing (AM) has advanced from design and fitting validation to biomedical, rapid tooling, tissue engineering, the arts and even food manufacturing. The corresponding scale reduction did not coincide with improving two of the most important process characteristics, namely print accuracy and build time. In this paper we introduce a computational framework for computing the maximum build volume for given non-circular extruders and printing machines that have 2, 3 and perhaps higher number of degrees of freedom (DOF). The proposed method also outputs the accessible configuration space of a multi-DOF AM machine that is instrumental in planning the final (temporal) motion of single or multiple print heads. Furthermore, we show that the proposed method allows the ranking of multiple extruders based on their volumetric deviation from nominal geometry. This formulation makes no assumption about the number of machine DOFs, nor about the planarity of the target contour, making...

Neuro-fuzzy control of the process of feeding wire material in additive technologies of the FDM family

FDM-based 3D-printing is one of the most common kinds of additive technologies. A typical printing unit consisting of a material feeding device and a printing head has a number of significant drawbacks associated with the lack of control over the basic parameters of extrusion. Basically, the only controlled parameter is the heating temperature. The article considers an alternative point of view on the problem, based on the multiagent approach and on elements of fuzzy and neural-fuzzy logic, which allows, through the introduction of additional feedbacks and simultaneous consideration of several basic parameters, to improve the quality of material extrusion, and to reduce the influence of the wire-material quality on the final 3D-printing result.

Newly developed UV-curable inkjet technology for forming high quality image with high productivity

We have developed a new and unique UV-curable inkjet technology for a sheet-fed inkjet digital press AccurioJet KM-1, which achieves offset like high quality image with high productivity; 3,000 sheets per hour. A number of AccurioJet KM-1 have already run in the production lines of customers, and have gained reputation as "Real Digitalization Pioneer" for commercial printing industry. The single-pass inkjet printing technology, one of the key technology for the high productivity, is still a big challenge for image processing. To avoid the dots coalescing, we developed a new ink formulation and curing process which can control the ink viscosity precisely in the print head and on the recording media. We also improved the technology which can control the gloss level of the image. Combining them, we succeeded to develop a printing system which achieves offset like high quality image with high productivity.

Biosensor Based on Screen-Printed Electrode and Glucose-Oxidase Modified with the Addition of Single-Walled Carbon Nanotubes and Thermoexpanded Graphite

The modification of an electrode produced by a matrix printing head with the use of glucose oxidase (GOD), single-walled carbon nanotubes (SWCNTs), and thermoexpanded graphite (TEG) has been studied. During glucose oxidation, modification by SWCNTs leads to the effect of direct electron transfer. Both nanomaterials increase the magnitude of the sensitivity coefficient (SC) from 0.11 to 0.24 mA M–1 in the case of glucose oxidase–and ferrocene-based electrodes when modification is done with the addition of TEG and up to 0.62 mA M–1 when modification is done with the addition of SWCNTs. A comparison of the characteristics of the biosensors with ferrocene and nanomaterials with those of the mediator-free biosensors based on SWCNTs and GOD shows that the biosensor provides higher sensitivity detection; the magnitude of sensitivity coefficient is 1.5 mA M–1. The higher magnitude of the SC can be explained by the occurrence of more effective electron transfer from active centers of the enzyme to the electrode. Voltammetric measurements demonstrate that electron transfer in a mediator-free biosensor is not complicated by a chemical reaction and is carried out under the control of diffusion factors. After testing the mediator-free biosensor in practice, it is possible to talk about the applicability of such a biosensor in detecting glucose in different environments, including the fermentation industry.

Compensation of image noise induced by difference in optical characteristics of array-LED chips of LED print head

There are various applied electro-optical devices, which utilize light emitting didoe (LED) chip array for applications to displays and opto-electronic sensors. In those devices, it is the one of the critical technical issues to minimize uncertain fluctuations including optical power and optical density. Due to variation in operating environment of a device, those are not corrected precisely by controlling parameters based on simple relation between parameters and resultant abovementioned outputs. Therefore, there is essential need to correct outputs in real-time based on correction function generated from the consideration on various operation condition. In this article, we introduce an output correction method through reporting real-time image noise reduction in the application to electro-photography with LED print head. In the technology of LED print head, as differences in optical characteristics between each LED cause vertical image noise, it should be corrected in order to obtain images that are comparable or better in quality compared to those produced by the conventional laser scanning method. Even though it seems that the method used to obtain uniform light power from each LED can solve this problem, it does not work well for high-resolution printing. Therefore, a scan method involving correction by a printed and scanned pattern is introduced through this work. The scan method is composed of correction patterns to minimize printing noise by its shape, the correction algorithm to calculate the optimized value and the printing algorithm to control gray levels in real-time precisely. We believe that the developed correction method upgrades the printing quality of the LPH printer better than commercial printers. The developed correction method can also be applied to various application areas that use an array-type light source such as display systems and lighting systems.

A Thermal Ink-Jet Printer Head Prototype With Full Carbon Based Microbubble Generator

This paper presents the development of a novel thermal ink-jet printer head prototype using full carbon-based microbubble generators with carbon nanotubes as heating elements and graphene as electrodes. Meanwhile, each microbubble generator is equipped with a carbon nanotube sensor to real-timely probe the temperature of its surrounding micro-environment. With an array of microbubble generators and sensors fabricated on quartz glass, as well as a microfluidic structure constructed by the micromachined silicon, the printer head prototype is formed by an anodic silicon-glass bonding process with several scattered graphene film flakes as medium. Droplet ejection with volume as tiny as ~0.03 pl corresponding to a very high spatial resolution of >2000 dpi driven by two microbubble valves is demonstrated by the printing unit in the prototype. Increasing the input power cannot only speed up the bubble nucleation and growth, but also improve the utilizing efficiency of electric heating energy. The experimental detected temperature variation in the printing unit reveals its nonlinear heat convection property by comparison with the theoretical calculation by finite-element analysis. [2017-0048]

Comparison of innovative metallization approaches for silicon heterojunction solar cells

Within this study, different metallization approaches were investigated and compared with respect to their applicability for silicon heterojunction (SHJ) solar cells. A printed line width of 34 µm with an aspect ratio of 0.59 was reached by double fine-line screen printing. In parallel, ink jet printing and its applicability regarding in-situ curing was evaluated. It was found that spreading of the ink is substantially reduced by choosing the optimum substrate temperature, enabling for a line width of 32 µm. Successful dispensing of a low-temperature silver paste was achieved by using a ten nozzle print head. By means of screen printed contact grids on both sides, solar cells with a conversion efficiency of 21.9 % were produced with industrial precursor wafers.

Synthesis of CoAl2O4/Al2O3 nanoparticles for ceramic blue pigments

Abstract The demand for pigments for industrial ceramic ink-jet printing is increasing steadily. The main challenge is the availability of ceramic pigments comprised of small-sized particles in order to avoid clogging of the printer head nozzle. This work presents a novel way to prepare ceramic blue pigment as a shell/core structure of CoAl 2 O 4 /Al 2 O 3 nanoparticles through a simple and low-cost process. In this process, the colour tone of nano-pigment can be tuned by the selection of the cobalt precursor/Al 2 O 3 ratio and calcining temperature.

Universal Micromachining Platform and Basic Technologies for the Manufacture and Marking of Microphysiological Systems.

Micro Physiological Systems (MPS), also known as Multi-Organ-Chip, Organ-on-a-Chip, or Body-on-a-Chip, are advanced microfluidic systems that allow the cultivation of different types of cells and tissue in just one common circuit. Furthermore, they thus can also adjust the interaction of these different tissues. Perspectival MPS will replace animal testing. For fast and flexible manufacturing and marking of MPS, a concept for a universal micromachining platform has been developed which provides the following latest key technologies: laser micro cutting of polymer foils, laser micro- and sub-micro-structuring of polymer foils, 3D printing of polymer components as well as optical inspection and online process control. The combination of different laser sources, processing optics, inspection systems, and print heads on multiple axes allows the change and exactly positioning to the workpiece during the process. Therewith, the realization of MPS including 3D printed components as well as direct laser interference patterned surfaces for well-defined cell adhesion and product protection is possible. Additional basic technologies for the generation of periodical line-like structures at polycarbonate foils using special Direct Laser Interference Patterning (DLIP) optics as well as for the 3D printing of fluid-tight cell culture reservoirs made of Acrylonitrile Butadiene Styrene directly onto polycarbonate microfluidics were established. A first prototype of the universal micromachining platform combining different lasers with Direct Laser Writing and DLIP is shown. With this laser micro cutting as well as laser micro-structuring of polycarbonate (PC) foils and therewith functionalization for MPS application could be successfully demonstrated.

Process for fabricating microactuator membranes of piezoelectric inkjet print head using multi‐step deep reactive ion etching process

As part of an effort to develop piezoelectric inkjet print head (PIPH), a process for fabricating its Si-cups and actuator membranes of multi-layered structures was investigated. The manufacture of this device was enabled by the use of deep reactive ion etching (DRIE). Based on that, multi-step DRIE process was proposed to etch the multi-layered actuator membranes on silicon on insulator wafers. Due to the appropriate parameters of the etching process, undesirable effects, such as Si grasses, notching effect of Si-cups and the bowing formation on the sidewalls, were also avoided. The way to eliminate the over-etching of SiO2 membranes by controlling the appropriate platen power and process duration simultaneously was also presented. High quality PIPH actuator membranes were finally obtained, making great contributes to the successful inkjet test.

디지털 프린팅 방식 3차원 프린터의 출력 시간 및 재료 사용량 예측 방법

This paper describes a method of precise estimation for printing time and material consumption which are directly related to the 3D printing cost. Printing process and head motion of 3D printers using digital printing head, which is analyzed by its digitized steps, is rapidly simulated without slicing to calculate estimated printing results. Using this method, printing time and material usage of 3D printer were estimated quickly and precisely and compared to the real printing result. Applying compensation using the printing parameters, transferred from the 3D printer to the printing estimation system, even more accurate estimation is achieved. This method is used in the 3D Sprint software.