Print Head Research Articles

Comparision of tribological behaviour for parts fabricated through fused deposition modelling (FDM) process on abs and 20% carbon fibre PLA

Fused deposition modelling (FDM) is a modern rapid prototyping technique which is used colossally for its ability to build applicable components in an equitable time. It is a 3D printing technique where the constituents are printed by supplementing the heated engineering plastic material layer by layer through a print head nozzle. So far engineered thermoplastics like Acrylonitrile Butadiene Styrene (ABS), carbon fibre poly lactic acid (CFPLA), polyamide, etc were used for parts production in this realm. During the itinerary of process engineering plastics may undergo wear because of the real time processing conditions like high pressure, temperature etc. In this experimental investigation a comparative study on tribological properties was performed on parts fabricated by FDM technique for 20% CFPLA and ABS specimens. The process parameters considered in this study are layer thickness, infill pattern and infill density. A series of Pin-on-disc tests by varying normal load and sliding speed, essentially a materials tribology test is used to screen the materials for the tribological properties (wear rate and coefficient of friction). In this study the layer thickness contribute to the wear at a direct proportion because as the thicker one would last long to wear and reach substrate because of its size. The infill pattern is indirectly proportional to the wear rate.

Dynamic Capillary-Driven Additive Manufacturing of Continuous Carbon Fiber Composite

Additive manufacturing (AM) of lightweight and energy-efficient composites using continuous carbon fibers and thermosetting polymers offers great opportunities for advancing composite manufacturing with design flexibility, low cost, reliability and repeatability, with potential use in a wide range of applications. However, to date there has been no AM technique reported to process continuous carbon fibers and thermosetting polymers for direct 3D printing. The temperature-dependent viscosity of thermosetting polymers suffers a significant decrease before the composite suddenly turns into a solid, making it difficult to infuse the polymer into the fiber structure and quickly cure the composite into a solid while retaining the desirable pattern during the additive manufacturing process. Here, we overcome these difficulties and report a dynamic capillary-driven AM approach, called localized in-plane thermal assisted (LITA) 3D printing, with a controllable viscosity and degree of curing of polymer to enable its fast and near-simultaneous infusion and curing to implement in situ solidification of composites into arbitrary shapes. Using the LITA technique, we developed a robotic system consisting of a uniquely designed printing head and an automated robot arm, yielding a 3D printer that enables us to print a composite on 2D and 3D substrates or in free space. The printed composite had high fiber volume fraction (60%) and degree of curing (95%) with high mechanical strength (810 MPa) and modulus (108 GPa).

Detection of System Compromise in Additive Manufacturing Using Video Motion Magnification

Abstract Three-dimensional printing systems have expanded the access to low cost, rapid methods for attaining physical prototypes or products. However, a cyber attack, system error, or operator error on a 3D-printing system may result in catastrophic situations, ranging from complete product failure, to small types of defects which weaken the structural integrity of the product. Such defects can be introduced early-on via solid models or through G-codes for printer movements at a later stage. Previous works have studied the use of image classifiers to predict defects in real-time and offline. However, a major restriction in the functionality of these methods is the availability of a dataset capturing diverse attacks on printed entities or the printing process. This paper introduces an image processing technique that analyzes the amplitude and phase variations of the print head platform arising through induced system manipulations. The method uses an image sequence of the printing process to perform an offline spatio-temporal video decomposition to amplify changes attributable to a change in system parameters. The authors hypothesize that a change in the amplitude envelope and instantaneous phase response as a result of a change in the end-effector translational instructions to be correlated with an AM system compromise. Two case studies are presented, one verifies the hypothesis with statistical evidence in support of the method while the other studies the effectiveness of a conventional tensile test to identify system compromise. The method has the potential to enhance the robustness of cyber-physical systems such as 3D printers.

A comprehensive study on the droplet formation processes and its influencing factors of a tubular piezoelectric print head

Various inks with different properties are widely used in the printed electronic industry. In order to obtain high quality inkjet printing, it is necessary to study the droplet formation process and its influencing factors comprehensively. Only in this way, the incentive conditions and liquid physical parameters of droplet ejection can be obtained and optimized. Firstly, the calculation model of the droplet ejection process is established for a tubular print head and the boundary conditions are set according to the driving characteristics. Secondly, the free surface flow is calculated in the simulation software and sequential pictures of the droplet formation processes are captured to validate the availability of the numerical algorithm. Finally, the droplet formation processes of the tubular piezoelectric print head are simulated under different incentive conditions, different viscosities and different surface tensions. Too small a driving energy is insufficient to cause the head to eject droplets. Excessive excitation energy will result in larger or multiple satellite droplets. Additionally, the thinning process of the liquid neck is examined carefully in this paper. Results show that surface tension and viscosity have a significant effect on the thinning speed of the liquid neck, but the effect is not as significant as previous studies.

Agent based modeling to optimize workflow of robotic steel and concrete 3D printers

Abstract At a time when construction projects are increasing in complexity and costs are constantly rising, 3D concrete printing have emerged as a revolutionary technology in construction. However, reinforcing 3D printed concrete elements has posed technical issues in research and practice. This paper introduces a methodology for 3D printing nonstandard steel rebar shapes together with 3D concrete printing. The new process can revolutionize the construction industry's approach to reinforced concrete design, as it provides a high degree of flexibility in both concrete and steel free-form creation, which is a key difference from traditional methods that only utilize standard steel reinforcement shapes. In addition, the proposed method will provide an even higher degree of automation in the concrete 3D printing construction process. An agent based model using Any Logic© was developed to simulate and optimize the printing of retaining and shear walls for a floor in a reinforced concrete building. Results show the optimization ratios of steel printing heads to concrete printing heads using the current technology and promise significant reductions in time and cost while providing a cleaner, safer, more automated, and an unbounded construction process. Findings from this research call for an in-depth investigation of the capabilities of steel 3D printing and its utilization in construction. It also highlights the importance of considering the application of new construction tools that would cope with the rapid growth of computational capabilities, and their adoption in design practices.

An approach to partition workpiece CAD model towards 5-axis support-free 3D printing

This paper presents a new method to fabricate workpieces using a 5-axis printing equipment with similar movement way of 5-axis milling machine tools. The method includes two main steps: (i) CAD model is partitioned into several sub-parts using a gravity effect partition method simulating the material-falling process when the model is stacked along the Z direction. In our processing plan, every sub-part has a slice direction. Before printing a sub-part, we rotate A axis and C axis so that its slice direction exactly coincides with the Z axis positive direction and then materials are stacked along the slice direction; (ii) these sub-parts are sorted with printing-base constraint and interference-free constraint. The two constraints, respectively, mean that the previously printed sub-parts are used as the printing bases of subsequently printed sub-parts; there is no interference between printed sub-parts and the printer head. These partition and sort principles have been generalized as an optimization model to satisfy printing-base constraint, interference-free constraint, and shortest empty printing path constraint. Our printing processing-plan can be regarded as a process to solve the optimization model. We have successfully generated sub-part sequences for some CAD models with large overhangs and complex structures to verify the printing processing-plan method.

Manufacturability Oriented Model Correction and Build Direction Optimization for Additive Manufacturing

AbstractWe introduce a method to analyze and modify a shape to make it manufacturable for a given additive manufacturing (AM) process. Different AM technologies, process parameters, or materials introduce geometric constraints on what is manufacturable or not. Given an input 3D model and minimum printable feature size dictated by the manufacturing process characteristics and parameters, our algorithm generates a corrected geometry that is printable with the intended AM process. A key issue in model correction for manufacturability is the identification of critical features that are affected by the printing process. To address this challenge, we propose a topology aware approach to construct the allowable space for a print head to traverse during the 3D printing process. Combined with our build orientation optimization algorithm, the amount of modifications performed on the shape is kept at minimum while providing an accurate approximation of the as-manufactured part. We demonstrate our method on a variety of 3D models and validate it by 3D printing the results.

Preparation of 3DGP dense zirconia parts by two-step method:staggered stacking method and printing wire deformation

A new process, staggered stacking method of printing wires and printing wire deformation by 3D gel-printing, to prepare ZrO2 dense parts was used in this study. In order to reduce the gap between adjacent printing wires, a new type of stacking method-staggered stacking is proposed. The density of sintered parts prepared by staggered stacking method is about 88%. In order to eliminate the gap between the adjacent cylindrical printing lines, according to printing wire deformation and then adjusting the parameters, the printing head was used as a scraper to fill the gaps. The relative density of sintered body prepared by staggered stacking method of printing wires and printing wire deformation in this study is 98.86%, and the three-point bending strength of the parts is 496 ± 20 MPa.

Optimization of process parameters in fused filament fabrication (FFF) utilizing poly lactic acid (PLA)

This research was to find an optimum parameter in Fused Deposition Modelling, FDM. They are various type of printing parameter in 3D printing. The parameter that was focused on in this research are orientation, print head and layer thickness while other parameters will be fixed. This parameter was evaluated the mechanical properties of the printed parts. The mechanical properties will be performed on the specimen are tensile test and 3 point-bending tests. The data were analyzed using Taguchi’s Method with orthogonal array of 9 level and Analysis of Variance, ANOVA. The highest of ultimate tensile strength was 34 MPa where the parameter were 34.592 MPa. The highest of flexural strength was 95.542 MPa. The optimum parameter for the tensile test was 25-degree of orientation, 0.4 mm of print head and 0.2 for layer thickness. The optimum parameter for 3-point-bending test was 0-degree of orientation, 0.4 mm of print head and 0.15 mm of layer thickness. This parameter did the mechanical test again for the validation test. The average ultimate tensile strength value for 25-degree of orientation, 0.4 mm of print head and 0.2 for layer thickness was 30.558 MPa. While the average of flexural strength for 0-degree of orientation, 0.4 mm of print head and 0.15 mm of layer thickness was 95.557 MPa.

An additively manufactured novel polymer composite heat exchanger for dry cooling applications

The work presented in this paper focuses on the design and thermal characterization of a novel polymer composite heat exchanger (HX) produced by an innovative additive manufacturing process. The heat exchanger represents a gas to liquid configuration in which the gas side removes heat from the liquid side in a cross-flow arrangement. The novel HX utilizes a cross media approach in which, unlike the conventional HXs, the hot and cold sides are directly connected to each other through high conductivity metal fiber fins on the gas side protruding through the walls of the liquid side, thus eliminating the wall resistance separating the hot and cold sides. The HX demonstrates superior thermal performance at reduced pressure drops while also benefiting from the lighter weight and the lower cost that the polymer structure introduces. A 350-W water-to-air heat exchanger was fabricated using a fused filament fabrication (FFF) technique with a novel/patent pending printer head which was developed to produce the metal fiber composite structure of the heat exchanger. The results of the heat exchanger characterization tests show that it yields up to 220% and 125% improvement in heat flow rate over mass (Q/m) and heat flow rate over volume (Q/V), respectively, when compared to comparable state-of-the-art plate fins HX configurations. This study in particular demonstrates the impact of additive manufacturing in realizing potentially transformative heat exchanger technologies that may otherwise be very difficult to achieve with conventional fabrication methods.

Simulation & modelling of dilute solutions in drop-on-demand inkjet printing: a review

This review is about the most important matters for advancing inkjet printing with a focus on piezoelectric droplet on demand (DOD) inkjet thin-film devices. The Nano material compounds can be incorporated into a polymeric matrix and deposited by piezoelectric inkjet printing. Current problems in advanced printers are discussed as embodied in liquid filament breakup along with satellite droplet formation and reduction in droplet sizes. Various model that predicts the printability of dilute, mono disperse polymer solutions in drop-on-demand “DOD” inkjet printing have been discussed. For satellite droplets, it is exhibited which liquid filament break-up treatment can be predicted via using a combination of two pi-numbers, including the Weber number. The layer was printed over other printed layers including electrodes composed of the conductive polymers and also several polymers. It has been discussed, some polymer materials are suitable for deposition and curing at low to moderate temperatures and atmospheric pressure, allowing for the use of polymers or paper as supportive substrates for the devices, and greatly facilitating the fabrication process. Furthermore, through this review, it has been discussed scaling analyses for designing and operating of inkjet heads. Because of droplet sizes from inkjet nozzles are typically on the order of nozzle dimensions, a numerical simulation is shown for explaining how to reduce droplet sizes through employing a novel input waveform impressed on the inkjet-head liquid inflow without changing the nozzle geometries. Regardless of their any less performance, inkjet printer head as a technique for the mentioned devices presents many advantages, the most notable of which are quickly fabricating and patterning, substrate flexibilities, avoidance of material wastage via applying “DoD” technologies.

Beyond the Toolpath: Site-Specific Melt Pool Size Control Enables Printing of Extra-Toolpath Geometry in Laser Wire-Based Directed Energy Deposition

A variety of techniques have been utilized in metal additive manufacturing (AM) for melt pool size management, including modeling and feed-forward approaches. In a few cases, closed-loop control has been demonstrated. In this research, closed-loop melt pool size control for large-scale, laser wire-based directed energy deposition is demonstrated with a novel modification, i.e., site-specific changes to the controller setpoint were commanded at trigger points, the locations of which were generated by the projection of a secondary geometry onto the primary three-dimensional (3D) printed component geometry. The present work shows that, through this technique, it is possible to print a specific geometry that occurs beyond the actual toolpath of the print head. This is denoted as extra-toolpath geometry and is fundamentally different from other methods of generating component features in metal AM. A proof-of-principle experiment is presented in which a complex oak leaf geometry was embossed on an otherwise ordinary double-bead wall made from Ti-6Al-4V. The process is introduced and characterized primarily from a controls perspective with reports on the performance of the control system, the melt pool size response, and the resulting geometry. The implications of this capability, which extend beyond localized control of bead geometry to the potential mitigations of defects and functional grading of component properties, are discussed.

Shear‐Driven Direct‐Write Printing of Room‐Temperature Gallium‐Based Liquid Metal Alloys

Gallium‐based metal alloys have high electrical conductivity in the liquid state at room temperature. These liquid metal conductors inspire unique electronic applications such as reconfigurable circuits and stretchable components with extremely high strain tolerance. Previously, liquid metals have been successfully patterned via direct‐writing, yielding metallically conductive features on‐demand at room temperature that do not require post‐processing, down to a resolution of ≈10 μm. While most direct‐write processes extrude materials from a nozzle via pressure or volumetric displacement, liquid metal is instead printed here by a shear‐driven mechanism that occurs when the oxide‐coated meniscus of the metal adheres to the printing substrate and is “pulled” from the nozzle at pressures that are well‐below that needed to extrude the metal in the absence of shear. Herein, the key operating parameters that enable shear‐driven printing of liquid metals including dispensing pressure, choice of substrate, print height, the surrounding environmental conditions, and the speed and acceleration of the print head are elucidated. A guide to the best practices as well as limitations for implementing shear‐driven printing of liquid metals at room temperature is provided in these studies.

Improved droplet watch system for photographing the forming process of a single droplet

Piezoelectric print heads (PPHs) are widely used in advanced technology applications including electronic skins, biosensors, and 3D printing and in the manufacture of electronic devices. Researchers can rapidly improve the droplet quality by visualizing the droplet-forming process. The existing droplet watch system (DWS) synthesizes an image of multiple droplets at different times to visualize the droplet-forming process; however, this requires all such processes to be consistent. If the process is inconsistent, it cannot be visualized easily using existing methods. In this study, we proposed an improved DWS based on the existing DWS. The improved DWS can photograph the forming process of a single droplet; therefore, even inconsistent droplet-forming processes can be recorded. Experimental results show that the improved DWS can clearly record the forming process of a single droplet.

Projektowanie kanału chłodzącego z użyciem natychmiastowych symulacji komputerowych oraz technik addytywnych

The methodology for designing of the prototype of cooling channel tailored to work with printing head mounted in industrial 3D printer is presented. Modern tools to optimize mechanical structures using so-called immediate simulations – ANSYS Discovery – and additive methods as a tool for the production of optimized components were used. Paper includes results of application research which were verified by non-contacts experimental methods like thermovision measurements and temperatures control at selected points of channel.

Processing of carbon fiber for 3D printed continuous composite structures

ABSTRACTThis article describes original carbon fiber impregnation procedure. The aim of this research is to determine carbon fiber impregnation process influence on mechanical properties of printed composite structures. 3D printing head and carbon fiber impregnation device were designed and produced. Three different polymer materials (PLA, PC, ABS) and solvent methylene chloride (DCM) were selected and solutions of different concentrations (2–10%) were prepared. 1 and 3K carbon fiber tow were impregnated with solutions (2–10%) and tensile tests of impregnated carbon fiber tow were performed. The correlation analysis revealed a strong relation between the tensile force of impregnated carbon fiber and mass of impregnated carbon fiber tow. For 3D printing 1 and 3K carbon fiber tow impregnated with 8 and 10% solutions were selected. Tensile tests were carried out to evaluate the mechanical properties of 3D printed composite structures. The obtained results revealed the dependency between the solution concentration and tensile strength, i.e. the higher the concentrations in carbon fiber impregnated with solution, the higher the tensile strength. This tendency is strong in PLA and PC impregnated 3K carbon fiber, however when the carbon fiber impregnated with ABS solution, the change in the results was not so significant. The obtained results can be used for the future development of different 3D printed composite structures.

3D printing using powder melt extrusion

Additive manufacturing promises to revolutionize manufacturing industries. However, 3D printing of novel build materials is currently limited by constraints inherent to printer designs. In this work, a bench-top powder melt extrusion (PME) 3D printer head was designed and fabricated to print parts directly from powder-based materials rather than filament. The final design of the PME printer head evolved from the Rich Rap Universal Pellet Extruder (RRUPE) design and was realized through an iterative approach. The PME printer was made possible by modifications to the funnel shape, pressure applied to the extrudate by the auger, and hot end structure. Through comparison of parts printed with the PME printer with those from a commercially available fused filament fabrication (FFF) 3D printer using common thermoplastics poly(lactide) (PLA), high impact poly(styrene) (HIPS), and acrylonitrile butadiene styrene (ABS) powders (< 1 mm in diameter), evaluation of the printer performance was performed. For each build material, the PME printed objects show comparable viscoelastic properties by dynamic mechanical analysis (DMA) to those of the FFF objects. However, due to a significant difference in printer resolution between PME (X–Y resolution of 0.8 mm and a Z-layer height calibrated to 0.1 mm) and FFF (X–Y resolution of 0.4 mm and a Z-layer height of 0.18 mm), as well as, an inherently more inconsistent feed of build material for PME than FFF, the resulting print quality, determined by a dimensional analysis and surface roughness comparisons, of the PME printed objects was lower than that of the FFF printed parts based on the print layer uniformity and structure. Further, due to the poorer print resolution and inherent inconsistent build material feed of the PME, the bulk tensile strength and Young’s moduli of the objects printed by PME were lower and more inconsistent (49.2 ± 10.7 MPa and 1620 ± 375 MPa, respectively) than those of FFF printed objects (57.7 ± 2.31 MPa and 2160 ± 179 MPa, respectively). Nevertheless, PME print methods promise an opportunity to provide a platform on which it is possible to rapidly prototype a myriad of thermoplastic materials for 3D printing.

Design and fabrication of composite vibrating plate used for piezoelectric inkjet print head

A piezoelectric vibrating plate is an important component of the piezoelectric inkjet print head, it determines the ejection performance of the piezoelectric inkjet print head. Based on the design model of the vibrating plate and the lead zirconate titanate piezoelectric film in the inkjet print head, the approximate expression of the equivalent load and deflection of the vibrating plate were established. The Cu/SiO2 vibration plate structure of the piezoelectric inkjet print head was fabricated based on MEMS process. The laser Doppler test was performed on the vibrating plate to obtain the amplitude of the Cu/SiO2 vibrating plate. The test results are in good agreement with the theoretical predictions based on the mechanical analysis.

High-throughput characterization of fluid properties to predict droplet ejection for three-dimensional inkjet printing formulations

Inkjet printing has been used as an Additive Manufacturing (AM) method to fabricate three-dimensional (3D) structures. However, a lack of materials suitable for inkjet printing poses one of the key challenges that impedes industry from fully adopting this technology. Consequently, many industry sectors are required to spend significant time and resources on formulating new materials for an AM process, instead of focusing on product development. To achieve the spatially controlled deposition of a printed voxel in a predictable and repeatable fashion, a combination of the physical properties of the ‘ink’ material, print head design, and processing parameters is associated. This study demonstrates the expedited formulation of new inks through the adoption of a high-throughput screening (HTS) approach. Use of a liquid handler containing multi-pipette heads, to rapidly prepare inkjet formulations in a micro-array format, and subsequently measure the viscosity and surface tension for each in a high-throughput manner is reported. This automatic approach is estimated to be 15 times more rapid than conventional methods. The throughput is 96 formulations per 13.1 working hours, including sample preparation and subsequent printability determination. The HTS technique was validated by comparison with conventional viscosity and surface tension measurements, as well as the observation of droplet ejection during inkjet printing processes. Using this approach, a library of 96 acrylate/methacrylate materials was screened to identify the printability of each formulation at different processing temperatures. The methodology and the material database established using this HTS technique will allow academic and industrial users to rapidly select the most ideal formulation to deliver printability and a predicted processing window for a chosen application.

Flow analysis of the polymer spreading during extrusion additive manufacturing

The spreading of molten polymer between the moving printing head and the substrate in extrusion additive manufacturing is studied. Finite element computation and an analytical model have been used. The hypotheses of the analytical model are qualitatively justified by the results of the numerical computation. The analytical calculation is a powerful tool to rapidly evaluate the relationships between processing parameters (extrusion rate, printing head velocity, gap between the printing head and the substrate) and some characteristics of the deposition (dimensions of the deposited filament, pressure at the printing head nozzle, separating force between substrate and printing head). An isothermal hypothesis is discussed. The viscous non-Newtonian behavior is accounted for through an approximate shear thinning power law model. A printing processing window is defined following several requirements: a continuous deposit, without spreading in front of the printing head, maximum and minimum spreading pressures, an upper-limit for the separating force between head and substrate.