Extrusion Devices Research Articles

Tracing the Evolution of 3-D Printing Technology in China Using LDA-Based Patent Abstract Mining

3-D printing is an additive manufacturing process, which enables products to be custom designed. Obtaining the evolution trend and identifying the potential R&D hotspots of 3-D printing technology are important strategic issues for both nations and enterprises. In this article, a combination method is proposed using the Viterbi algorithm to identify technological terms in patents, using the latent Dirichlet allocation model to capture potential technological topics in patents, and using the hidden Markov model to analyze the distribution and evolution pattern of the technological topics. Based on the results, technological topics and future R&D hotspots in 3-D printing are identified. Among the technological topics, extrusion devices and laser powder molding are gradually losing R&D; model acquisition, extrusion devices, rotary printing, and denture are the key topics of technological evolution that are difficult to overcome; laser focusing, print head, color printing, recyclable, feeding, control panel, and denture will become the focus of R&D in the near future. Finally, a comparison and experiments are given to demonstrate the plausibility of our method.

Methodology for the additive manufacture of embedded conductive paths connecting microelectromechanical sensors using conductive and flexible filaments with extrusion devices

Purpose The purpose of this study is to explore a methodology for connecting microelectromechanical system sensors – i.e. inertial measurement unit (IMU) – to an Arduino-based microcontroller, using graphene-based conductive filament and flexible thermoplastic polyurethane (FTPU) filament and low-cost dual material extrusion technology. Design/methodology/approach A series of electrical tests were carried out to determine the maximum resistance the conductive paths may take to connect printed circuit boards (PCB). To select the most suitable printing material, three types of conductive filaments were examined. Then an experiment was carried out to find the best printing parameters in terms of printing speed, printing temperature and layer height to minimise resistivity. The size of the conductive path was also analysed. A final prototype was designed and printed according to optimised printing settings and maximum allowable resistances for each line and considering different geometries and printing strategies to reduce cross-contamination among paths. Findings For the Black Magic 3D conductive filament, the printing speed and layer height played a significant role regarding resistivity, while the printing temperature was not very important. The infill pattern of the conductive paths had to be aligned with the expected current path, while using air gaps between two adjacent paths resulted in the best approach to reducing cross-contamination. Moreover, the cross-section size of the conductive path did not affect the volume resistivity. When combined with FTPU filament constraints, the prototype yielded suitable electrical performance and printing quality when printed at a temperature of 220°C, speed of 20 mm/s and layer height of 0.2 mm. Originality/value This paper explores a systematic methodology for the additive manufacturing of commercial conductive material using low-cost extrusion technology to connect complex electronics when data transmission is a key feature.

Large-sized graphene oxide as bonding agent for the liquid extrusion of nanoparticle aerogels

Self-assembly strategies have been widely used to prepare aerogels from nanoparticles. It is challenging to assemble those nanoparticles whose surface is lack of abundant polar functional groups into aerogels, as the weak interface interactions among nanoparticles are not enough to maintain aerogel structures. Here we demonstrate a liquid extrusion strategy as a possible solution to this challenge, by using a small amount of large-sized graphene oxide and liquid extrusion devices. Large-sized graphene oxide sheets cover, wrap and assemble nanoparticles, and thus promote the assembly of nanoparticles. Extrusion devices are employed to control the shape and size of aerogels. Based on this strategy, a variety of nanoparticle, such as clay nanosheets, boron nitride nanosheets and carbon nanotubes, have been assembled into aerogels with designed shape and size even when there are few polar functional groups on nanoparticle surface. Detailed studies on clay aerogels show that the aerogels have porous structure and high performance, which can be proposed for applications in thermal insulation, fire retardation and absorption, etc. This liquid extrusion strategy can be thought of as effective, general and scalable approach to produce nanoparticle aerogels, particularly for those nanoparticles whose surface is lack of polar functional groups.

COMPUTATIONAL FLUID DYNAMICS SIMULATION OF SINGLE SCREW EXTRUDERS IN CABLE INDUSTRIES

The flow of polymer pellets along the solid conveying screw of a single screw extruder is studied by use of a numerical model based on the Finite Volume Method (FVM). The screw profile of existing Nokia-Malifer plastic extrusion devices (for cable industries) was mesured.Model predictions used is the Power law for Non-Newtonian Fluid, the results are compared with experimental data, showing a good match. The feasiability of using CFD models for designing plastic extrusion devices is analyzed. Basic parameters such as temperature, velocity profiles and pressure show high degree of similarity to practical results.

Preface

In this special issue of the European Journal of Applied Mathematics we celebrate the 75th birthday of its founding editor, Professor John Ockendon.John started his research career with his D.Phil., awarded in 1965, working with Alan Tayler at the University of Oxford. John's background was in fluid mechanics, covering a wide range of topics, including, lubrication flows, flows in porous media, hypersonic aerodynamics, sloshing phenomena, and flow separation. He soon became involved in industrial research which led, in particular, to his interest in the field of free boundary problems, an area in which he became a driving force, through papers, conferences, and particularly through the fostering of regular international meetings and personal interactions. His pioneering work in the field was particularly concentrated in diffusion-controlled moving boundary problems that arise in various applications, such as in phase change problems, elastic-contact problems and the fundamental Hele-Shaw free boundary problem. The industrial collaborations also led to mathematical studies of lens design, fibre extrusion, fluidised beds, glass manufacture and semiconductor devices, to name but a few, and to problems in scattering and wave theory, non-linear wave propagation and non-linear oscillations, as well as mechanics and heat and mass transfer. He continues to work on PDEs and asymptotics applied to new well-founded models from the real world, with a particular focus in the physical and earth sciences.

Alginates as a useful natural polymer for microencapsulation and therapeutic applications

Abstract This review outlines the role of alginates in microencapsulation and therapeutic applications. It focuses on the physicochemical properties of alginates (e.g. viscosity, thermo-stability, sol–gel transformation and drug release) to gain better insight into their potential medical applications, particularly for wound care and therapeutics. In order to understand how alginates can be optimized as a useful delivery system for therapeutic applications, various factors that impact drug release from alginate matrices (e.g. types of cations used in cross-linking, porosity of alginate matrices, pH effect, alginate composition, molecular weight of encapsulated drugs and modification of the functional groups in alginates) are also discussed. More specifically, practical applications of the cross-linking mechanism and sol–gel transformation property of alginates are explored to assess their potential to improve the mechanical properties of alginate dressings, to impart anti-microbial properties for treating wound infections and to develop products for tissue repair and wound healing. Innovative processes of developing alginate carriers and delivery systems and their recent applications are also discussed. Strategies employed to improve gelation of alginates commonly target the formulation by the inclusion of non-gelling cations or sequestrants during cross-linking. The application of other strategies, such as hot-made alginate gel method, in situ gelation method, crystal gun method, acoustic excitation method, and the use of extrusion devices with improved design are reviewed.

A novel design for hot-melt extrusion pelletizers

In this work we investigated a novel die design for the scale-up of hot melt extrusion (HME) devices for direct pelletization of pharmaceutics. Therefore we analyzed the temperature distribution in a lab- and production-scale die as well as melt flow through the die. Finally we explored the possibilities of an inner rotating knife for stabilizing melt flow. The work was based on computational fluid dynamics for simulating non-Newtonian melt flow and corresponding temperature fields. The results show that a tight temperature control of the die material is necessary to guarantee a safe scale-up of the process. Even in lab-scale applications temperature inhomogeneities have been observed both experimentally as well as in the simulation. These inhomogeneities act as an trigger to destabilize melt flow and hence could lead to a shutdown of the process. The proposed inner rotating knife acts as a pulsating device and consequently is able to enhance process stability. However, due to heat dissipation in the small gap between rotor and stator, this device has to be fitted with a separate low-speed drive and cannot be coupled directly to the main extruder shaft.

PVC‐ein werkstoff im wandel

AbstractThe consumption of PVC amounts to 5.3 Mio t in Western Europe with an annual increase of about 2%. The most important field of application is building and construction.The main targets relating to the production process are less energy consumption, the reduction of emissions to air and water and the increase of the productivity of the plants.In the field of processing a dramatic increase of the output of extrusion or calandering devices has been realized ‐ connected with an improvement of quality and economy.

Large-Scale Production of Liposomes of Defined size by a New Continuous High Pressure Extrusion Device

A new continuous high pressure extrusion apparatus for the generation of liposomes was designed and tested in the present study. The extruder, which basically consists of an open supply vessel and a high pressure filter holder mounted on a gas-driven pump exhibited superior abilities compared to currently available, discontinuous extrusion devices. Due to continuous flows up to 500 ml/min (filter diameter 47 mm), large batches on a liter scale could be extruded in one step. The maximum pressure of 10.5 MPa employed here, enabled the rapid passage of liposomal preparations with various lipid compositions at lipid concentrations as high as 400 mg/g through polycarbonate membranes without any clogging of the system. Employing final pore sizes between 5.0 and 0.03 μm, the mean vesicle diameter of liposomal preparations could be varied from 400 to 60 nm. Surprisingly high encapsulation efficiencies of two water-soluble contrast agents, iopromide and Gd-DTPA, which we used as model substances, were obtained for...

The conversion of brown coal to a dense, dry, hard material

A technology has been developed for transforming run-of-mine brown coals into a dense, dry, hard product. Raw coal is attritioned in batch or continuous kneaders to a mean particle size of approximately 10 μm. This size reduction releases the water naturally occurring within the porous coal structure, such that a paste-like material results. The paste can then be easily formed into products of the desired shape and size by extrusion devices. A hard, low-moisture content briquette-equivalent product is produced by the evaporative removal of water at or near ambient atmospheric drying conditions. The resultant product exhibits considerable strength, which may be further improved by the addition of pH modifiers in the case of suitable coals. Advantages of this densified brown coal process are that a hard, dense, fuel product can be manufactured from a raw brown coal of high initial water content without the need for, or prolonged, expensive drying conditions at elevated temperature. The resultant product is suitable either as a briquette equivalent fuel, or as feedstock for the manufacture of smokeless fuels, chars and activated carbons. The product retains the Volatile and Fixed Carbon values of the raw coal but possesses a Net Wet Specific Energy equivalent to that of a high rank coal. The densified coal has an advantage over a black coal in that dependant upon the coal stock selected the mineral content can be quite low. The process is more general and has been applied to other feedstocks — a peat and some lignites as well as brown coals have been found suitable. The chemical analyses indicate the involvement of phenolic residues in the coal as reactive centres. Reactions of these residues are initiated by the shearing-attritioning step in which fresh and reactive surfaces of the coal particles are exposed. The reactive centres are brought together by extrusion allowing cross-linking reactions to occur during drying.

Rotary Extrusion Devices

ABSTRACT DEVELOPMENT work on rotary extrusion macera-tion devices at the University of Wisconsin -Madison is discussed, including problems encountered and the solutions devised. An analysis of the rotary configura-tions is presented with emphasis on feed angle and coeffi-cient of friction required for feeding.

Polyethylene flow data from melt viscometer and commercial extruder measurements

AbstractFor broad ranges of operating conditions and a wide variety of high pressure polyethylenes, the flow data obtained from a high shear viscometer and a commercial extruder are identical. Discrepancies between flow data can result from non steady state viscosities in the high shear viscometer, or from cooled screw extruder operation. In the broad regions in which the flow data concur, the readily obtained viscometer data are suitable for predictions of extruder performance. The principle is illustrated by the good correlation of a viscometer flow curve parameter and the screw power consumption in the extruder. Principles outlined for flow data identity and extruder performance prediction are believed to be general, but the quantitative limits defined are specific to the extrusion devices involved.