Fibre pulsing during melt electrospinning writing

2016 ◽  
Vol 17 (3-4) ◽  
Author(s):  
Gernot Hochleitner ◽  
Almoatazbellah Youssef ◽  
Andrei Hrynevich ◽  
Jodie N. Haigh ◽  
Tomasz Jungst ◽  
...  
Keyword(s):  
Additive Manufacturing ◽  
Processing Parameters ◽  
Simple Approach ◽  
Direct Writing ◽  
Melt Electrospinning ◽  
Printing Quality ◽  
Constant Diameter ◽  
Feeding Pressure ◽  
The Stability ◽  
Acceleration Voltage

AbstractAdditive manufacturing with electrohydrodynamic direct writing is a promising approach for the production of polymeric microscale objects. In this study we investigate the stability of one such process, melt electrospinning writing, to maintain accurate placement of the deposited fibre throughout the entire print. The influence of acceleration voltage and feeding pressure on the deposited poly(ε-caprolactone) fibre homogeneity is described, and how this affects the variable lag of the jet drawn by the collector movement. Three classes of diameter instabilities were observed that led to poor printing quality: (1) temporary pulsing, (2) continuous pulsing, and (3) regular long bead defects. No breakup of the electrified jet was observed for any of the experiments. A simple approach is presented for the melt electrospinning user to evaluate fibre writing integrity, and adjust the processing parameters accordingly to achieve reproducible and constant diameter fibres.

scholarly journals Measurement and Time Response of Electrohydrodynamic Direct-Writing Current

Micromachines ◽  
2019 ◽  
Vol 10 (2) ◽  
pp. 90 ◽  
Author(s):  
Gaofeng Zheng ◽  
Wendong Xue ◽  
Huatan Chen ◽  
Lingling Sun ◽  
Jiaxin Jiang ◽  
...  
Keyword(s):  
Applied Voltage ◽  
Signal To Noise Ratio ◽  
Polymer Concentration ◽  
Processing Parameters ◽  
High Signal ◽  
Electrical Characteristics ◽  
Direct Writing ◽  
The Stability ◽  
Impulse Current ◽  
Stable Stage

The micro/nano current is an important characteristic to reflect the electrohydrodynamic direct-writing (EDW) process. In this paper, a direct-written current measurement system with a high signal to noise ratio was proposed to monitor the charged jets, providing the data basis for the promotion of stability and precision of the EDW jet. The electrical characteristics of the printing process were studied, the electrohydrodynamic direct-written current was associated with the stability of charged jet and the accuracy of direct-written patterns. There was an impulse current when the front end of the jet reached the collector and then a stable jet could be gained. With the increase of applied voltage, the severe fluctuation of measured current increased, the charged jet became more unstable and the accuracy of direct-written parallel lines was lower. The effects of processing parameters on direct-written current were also investigated. The average direct-written current at the stable stage increased as the applied voltage and polymer concentration increased, and it decreased as the distance from the nozzle to the collector increased. This research will promote the development and applications of EDW technology in the fields of micro/nano manufacturing.

A Simple Approach to Evaluating the Stability of Optimal Portfolios

2014 ◽  
Author(s):  
Zhongjin Yang ◽  
Keli Han ◽  
Marat Molyboga ◽  
Georgiy Molyboga
Keyword(s):  
Simple Approach ◽  
Optimal Portfolios ◽  
The Stability

scholarly journals Development of an Additive Manufacturing System for the Deposition of Thermoplastics Impregnated with Carbon Fibers

2019 ◽  
Vol 3 (2) ◽  
pp. 35 ◽  
Author(s):  
Miguel Reis Silva ◽  
António M. Pereira ◽  
Nuno Alves ◽  
Gonçalo Mateus ◽  
Artur Mateus ◽  
...  
Keyword(s):  
Tensile Strength ◽  
Additive Manufacturing ◽  
Carbon Fibers ◽  
Low Cost ◽  
Deposition Process ◽  
Processing Parameters ◽  
Yarn Diameter ◽  
Thermoplastic Matrix ◽  
Anisotropic Mechanical Properties ◽  
Long Carbon Fiber

This work presents an innovative system that allows the oriented deposition of continuous fibers or long fibers, pre-impregnated or not, in a thermoplastic matrix. This system is used in an integrated way with the filamentary fusion additive manufacturing technology and allows a localized and oriented reinforcement of polymer components for advanced engineering applications at a low cost. To demonstrate the capabilities of the developed system, composite components of thermoplastic matrix (polyamide) reinforced with pre-impregnated long carbon fiber (carbon + polyamide), 1 K and 3 K, were processed and their tensile and flexural strength evaluated. It was demonstrated that the tensile strength value depends on the density of carbon fibers present in the composite, and that with the passage of 2 to 4 layers of fibers, an increase in breaking strength was obtained of about 366% and 325% for the 3 K and 1 K yarns, respectively. The increase of the fiber yarn diameter leads to higher values of tensile strength of the composite. The obtained standard deviation reveals that the deposition process gives rise to components with anisotropic mechanical properties and the need to optimize the processing parameters, especially those that lead to an increase in adhesion between deposited layers.

Additive Manufacturing of Glass

2014 ◽  
Vol 136 (6) ◽  
Author(s):  
Junjie Luo ◽  
Heng Pan ◽  
Edward C. Kinzel
Keyword(s):  
Additive Manufacturing ◽  
Glass Powder ◽  
Processing Parameters ◽  
Gradient Index ◽  
Continuous Line ◽  
Single Track ◽  
Laser Melting ◽  
Powder Bed ◽  
Transparent Parts ◽  
Insight Into

Selective laser melting (SLM) is a technique for the additive manufacturing (AM) of metals, plastics, and even ceramics. This paper explores using SLM for depositing glass structures. A CO2 laser is used to locally melt portions of a powder bed to study the effects of process parameters on stationary particle formation as well as continuous line quality. Numerical modeling is also applied to gain insight into the physical process. The experimental and numerical results indicate that the absorptivity of the glass powder is nearly constant with respect to the processing parameters. These results are used to deposit layered single-track wide walls to demonstrate the potential of using the SLM process for building transparent parts. Finally, the powder bed process is compared to a wire-fed approach. AM of glass is relevant for gradient index optics, systems with embedded optics, and the formation of hermetic seals.

Water Based Colloidal Processing of Ceramic Laminates

2007 ◽  
Vol 333 ◽  
pp. 39-48 ◽  
Author(s):  
Antonio Javier Sanchez-Herencia
Keyword(s):  
Processing Parameters ◽  
Colloidal Processing ◽  
Water Separation ◽  
Green Strength ◽  
Water Based ◽  
The Stability ◽  
Deflection Criteria ◽  
Joining Strength ◽  
Processing Techniques ◽  
Laminated Structures

Multilayered materials and coating are complex structures proposed among others to face the structural requirements of ceramics. The development of reinforcement mechanism by laminated structures can be due to deflection criteria or to the presence of residual stresses and requires of tailored laminates. These designs are characterized by the phases, thickness and distribution of the layers as well as the joining strength between them. In this sense water based colloidal processing techniques are used to fabricate layered structures by consolidating the layers from fluid dispersions of the powders in water. In these processing methods the phases presented in the final laminate are mainly given by the composition of the starting slurries while the changes in thickness and sharpness of the layers are controlled by acting on the processing parameters. The achievement of stable slurries is a shared step for all the colloidal processing techniques. In the water based slurries the stability will be dominated by the polar media, the surface behavior of the particles and the presence of dispersant additives to increase the repulsion between particles. The stable slurry ensures an effective milling and dispersion of the phases as well as high solid loadings, if required. Further processes associated to shaping and consolidation of the layers requires the incorporation of additives and-or water removal. The shaping methods based on aqueous slurries can be classified taking into account the process of solid-water separation. For each of those shaping methods, the nature and amount of the additives is different in order to get the optimum rheological behavior and green strength after drying. Depending on the thickness of layers and coatings as well as the shape and dimensions of the samples, the shaping method can be selected alone and combined with others.

Additive Manufacturing of Porous Ceramics with Foaming Agent

2021 ◽  
pp. 1-21
Author(s):  
Zipeng Guo ◽  
Lu An ◽  
Sushil Lakshmanan ◽  
Jason Armstrong ◽  
Shenqiang Ren ◽  
...  
Keyword(s):  
Additive Manufacturing ◽  
Ambient Pressure ◽  
Experimental Studies ◽  
Three Dimensional ◽  
Cost Effective ◽  
Tensile Tests ◽  
Porous Ceramics ◽  
Foaming Agent ◽  
Printing Quality ◽  
And Control

Abstract The macro-porous ceramics has promising durability and thermal insulation performance. As porous ceramics find more and more applications across many industries, a cost-effective and scalable additive manufacturing technique for fabricating macro-porous ceramics is highly desirable. Herein, we reported a facile additive manufacturing approach to fabricate porous ceramics and control the printed porosity. Several printable ceramic inks were prepared, the foaming agent was added to generate gaseous bubbles in the ink, followed by the direct ink writing and the ambient-pressure and room-temperature drying to create the three-dimensional geometries. A set of experimental studies were performed to optimize the printing quality. The results revealed the optimal process parameters for printing the foamed ceramic ink with a high spatial resolution and fine surface quality. Varying the concentration of the foaming agent enables the controllability of the structural porosity. The maximum porosity can reach 85%, with a crack-free internal porous structure. The tensile tests showed that the printed macro-porous ceramics possessed enhanced durability with the addition of fiber. With a high-fidelity 3D printing process and the precise controllability of the porosity, we showed that the printed samples exhibited a remarkably low thermal conductivity and durable mechanical strength.

Sinusoidal AC-induced electrohydrodynamic direct-writing nanofibers on insulating collector

2021 ◽  
pp. 2140009
Author(s):  
Huatan Chen ◽  
Guoyi Kang ◽  
Jiaxin Jiang ◽  
Juan Liu ◽  
Xiang Wang ◽  
...  
Keyword(s):  
Electric Field ◽  
Flexible Electronics ◽  
Direct Writing ◽  
Printing Process ◽  
Ac Electric Field ◽  
Jet Printing ◽  
Voltage Frequency ◽  
Fiber Deposition ◽  
The Stability ◽  
Application Fields

Printing orderly patterns on the insulating collector is the key for the development and application of flexible electronics. However, electrospinning on the insulating collector still has the problem of unstable jet due to the charge accumulation. The alternating current (AC)-induced electrohydrodynamic direct-writing (EDW) technology is a good way to decrease the interferences of charge repulsion, which is beneficial to printing orderly micro/nanostructures on the insulating collector. In this work, the sinusoidal AC-induced EDW is used to enhance the stability of charged jet and the deposition behaviors under AC electric field are also studied. The reciprocation transferring of charges induced by the AC electric field decreased the density of the accumulating charges on the insulating collector. The effect of AC electric field parameters on the direct-written micro/nanostructures are investigated to optimize the printing process. As the voltage peak increases, the fiber deposition bandwidth shows a trend of decreasing first and then increasing. Increasing the voltage frequency appropriately is beneficial to decrease the bandwidth of fiber deposition and to increase the stability of the jet. By improving the stability and controllability of the jet printing process, precise micro/nanopatterns can be direct-written on the insulating collector. This research provides a good foundation for expanding the application fields of EDW.

Bayesian Calibration of Multiple Coupled Simulation Models for Metal Additive Manufacturing: A Bayesian Network Approach

2021 ◽  
Author(s):  
Jiahui Ye ◽  
Mohamad Mahmoudi ◽  
Kubra Karayagiz ◽  
Luke Johnson ◽  
Raiyan Seede ◽  
...  
Keyword(s):  
Additive Manufacturing ◽  
Bayesian Network ◽  
Simulation Models ◽  
Processing Parameters ◽  
Network Approach ◽  
Structure Property ◽  
Coupled Simulation ◽  
Niobium Alloys ◽  
Powder Bed ◽  
Physical Phenomena

Abstract Modeling and simulation for additive manufacturing (AM) are critical enablers for understanding process physics, conducting process planning and optimization, and streamlining qualification and certification. It is often the case that a suite of hierarchically linked (or coupled) simulation models is needed to achieve the above task, as the entirety of the complex physical phenomena relevant to the understanding of process-structure-property-performance relationships in the context of AM precludes the use of a single simulation framework. In this study using a Bayesian network approach, we address the important problem of conducting uncertainty quantification (UQ) analysis for multiple hierarchical models to establish process-microstructure relationships in laser powder bed fusion (LPBF) AM. More significantly, we present the framework to calibrate and analyze simulation models that have unmeasurable variables, which are quantities of interest predicted by an upstream model and necessary for the downstream model in the chain that are difficult or impossible to observe experimentally. We validate the framework using a case study on predicting the microstructure of binary nickel-niobium alloys processed using LPBF as a function of processing parameters. Our framework is shown to be able to predict segregation of niobium with up to 94.3% prediction accuracy in test data.

Synchronization of Oscillators

2011 ◽  
pp. 247-260
Author(s):  
Jean B. Chabi Orou
Keyword(s):  
Chaotic Synchronization ◽  
Simple Approach ◽  
Short Introduction ◽  
Synchronization Process ◽  
The Stability ◽  
In The Beginning ◽  
Influence Of Noise ◽  
Synchronization Of Oscillators

A simple approach is proposed in this chapter to get started on the synchronization of oscillators study. The basics are given in the beginning such that the reader can get quickly familiar with the main concepts which lead to many kinds of synchronization configurations. Chaotic synchronization is next addressed and is followed by the stability of the synchronization issue. Finally, a short introduction of the influence of noise on the synchronization process is mentioned.

scholarly journals Temporal design for additive manufacturing

2020 ◽  
Vol 106 (9-10) ◽  
pp. 3849-3857
Author(s):  
S. Saliba ◽  
J. C. Kirkman-Brown ◽  
L. E. J. Thomas-Seale
Keyword(s):  
Additive Manufacturing ◽  
Time Domain ◽  
Processing Parameters ◽  
Software Pipeline ◽  
Novel Approach ◽  
Knowledge Propagation ◽  
End Use ◽  
The Time Domain ◽  
And Control ◽  
Design For Am

AbstractAdditive manufacturing (AM) is expected to generate huge economic revenue by 2025; however, this will only be realised by overcoming the barriers that are preventing its increased adoption to end-use parts. Design for AM (DfAM) is recognised as a multi-faceted problem, exasperated by constraints to creativity, knowledge propagation, insufficiencies in education and a fragmented software pipeline. This study proposes a novel approach to increase the creativity in DfAM. Through comparison between DfAM and in utero human development, the unutilised potential of design through the time domain was identified. Therefore, the aim of the research is to develop a computer-aided manufacturing (CAM) programme to demonstrate design through the time domain, known as Temporal DfAM (TDfAM). This was achieved through a bespoke MATLAB code which applies a linear function to a process parameter, discretised across the additive build. TDfAM was demonstrated through the variation of extrusion speed combined with the infill angle, through the axial and in-plane directions. It is widely accepted in the literature that AM processing parameters change the properties of AM materials. Thus, the application of the TDfAM approach offers the engineer increased creative scope and control, whilst inherently upskilling knowledge, in the design of AM materials.

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