Simulation of Polymer Melt Flow Fields in Intermeshing Co-Rotating Three-Screw Extruders

Three-dimension isothermal flows of polymer melt in the kneading blocks of triangularly-arranged and parallelly-arranged intermeshing co-rotating three-screw extruders are simulated using the finite element package POLYFLOW. Based on the velocity fields calculated, the particle trajectories in both machines are visualized using particle tracking technique. The numerical results indicate that the flow patterns in three-screw extruders are similar to those in twin-screw extruders. The triangularly-arranged three-screw extruder has the largest pumping capacity and also the highest extrusion stability in terms of flowrate fluctuation with screw rotation. The instantaneous mixing and cumulative residence time distribution （RTD） characteristics are also analyzed and compared with traditional intermeshing co-rotating twin-screw extruders. It is shown that the start section of the cumulative RTD curve for the triangularly-arranged machine has a small shoulder, which is attributed to the faster flow in the central region of this type of extruder.

Study on Hardware-in-loop Simulation of Twin-screw Extruder Experiment System

In order to facilitate the teaching of industrial processes and experiments on the twin-screw extruder control debugging,and be closer to the actual testing,to reduce the debugging costs and the risk of debugging process,the paper designs a hardware-in-loop simulation of twin-screw extruder experiment system which is closer to scene,low cost and high safety.The system through the establishment of twin-screw extruder’s mathematical model on computer to simulate the realistic system and there is hardware practicality in the computer simulation loop.The hardware based on C8051F020 can operate in the simulation loop in real time.In computer software design, we desigh man-machine interface that is intuitive and easy to operate,can reflect twin-screw extruder main operation information vividly.Finally,twin-screw extruder’s 3 heater temperature mathematical model and PID incremental control algorithm are presented.

Single-Screw Laboratory Extruder for Production of Expanded Products:Design,Construction and Performance Testing

In this study,a low-capacity single-screw cooking extruder for the manufacture of expanded snacks was designed based on theoretical models and guided operating data and practices of existing cooking extruders.Construction was carried out using locally available engineering materials in modest machine shops satisfying sanitary design criteria and tested using blends of cassava and defatted soybean flour.The extruder developed has throughput,screw speed,barrel diameter,length-to-diameter ratio and power requirement of 13.0 kg/h,200 rpm,40 mm,12 and 1.908 kW,respectively.The cost of the extruder developed was estimated N650,000 in 2016.Extrudates had expansion ratio and trypsin inhibitor reduction which ranged from 1.82 to 2.98 and 61.07%to 87.93%,respectively,across all treatments.This study demonstrates that a low-capacity and affordable experimental single-screw extruder can be designed and built domestically which can be scaled-up for pilot and industrial applications for the production of expanded snacks.

Development of a Powder Extruder System for Dual-pore Tissue-engineering Scaffold Fabrication

In this study,we developed a powder extruder system that can extrude and deposit powder mixtures to overcome the reported limitations of conventional dualpore scaffold manufacturing methods.To evaluate the extrusion and deposition capability of the powder extruder system,3D tissue-engineering scaffolds with dual-pore characteristics were fabricated with a PCL/PEO/NaCl(polycaprolactone/polyethylene oxide/sodium chloride)powder mixture.In addition,to evaluate the fabricated scaffolds,their compressive modulus,morphology,and in-vitro cell activity were assessed.Consequently,it was confirmed that the proposed powder extruder system can fabricate dual-pore scaffolds with well-interconnected pores as well as arbitrary 3D shapes shown by the fabrication of a 3D femur-shape scaffold similar to the femur model.The results of the cell proliferation and Cell Counting Kit-8(CCK-8)assays,DNA content analysis and viability assays confirm that the dual-pore scaffold fabricated by the powder extruder system improves cell attachment,proliferation,and viability.

Unsteady Flow of Shear-Thinning non-Newtonian Incompressible Fluid Through a Twin-Screw Extruder

The unsteady flow of viscous incompressible shear-thinning non-Newtonian fluid with mixed bound- ary is investigated. The boundary condition on the outflow is the modified natural boundary condition, it con- tains the additional nonlinear term, which enables us to control the kinetic energy of the backward flow. The global existence of weak solution is proved. The fictitious domain method which consists in filling the moving rigid screws with the surrounding fluid and taking into account the boundary conditions on these bodies by introducing a well-chosen distribution of boundary forces is used.

A desktop customised 3D printer with dual extruders to produce electronic circuitry

3D printing has opened new horizons for the manufacturing industry in general, and 3D printers have become the tools for technological advancements. There is a huge divide between the pricing of industrial and desktop 3D printers with the former being on the expensive side capable of producing excellent quality products and latter being on the low-cost side with moderate quality results. However, there is a larger room for improvements and enhancements for the desktop systems as compared to the industrial ones. In this paper, a desktop 3D printer called Prusa Mendel i2 has been modified and integrated with an additional extruder so that the system can work with dual extruders and produce bespoke electronic circuits. The communication between the two extruders has been established by making use of the In-Chip Serial Program- ming port on the Arduino Uno controlling the printer. The biggest challenge is to control the flow of electric paint （to be dispensed by the new extruder） and CFD （Computa- tional Fluid Dynamics） analysis has been carried out to ascertain the optimal conditions for proper dispensing. The final product is a customised electronic circuit with the base of plastic （from the 3D printer＇s extruder） and electronic paint （from the additional extruder） properly dispensed to create a live circuit on a plastic platform. This low-cost enhancement to a desktop 3D printer can provide a new prospect to produce multiple material parts where the additional extruder can be filled with any material that can be properly dispensed from its nozzle.

Chemical and mechanical properties of stainless, environment-friendly, and nonflammable Mg alloys (SEN alloys): A review

This review article provides overall understanding of stainless,environment-friendly,and nonflammable Mg alloys(SEN alloys)recently developed at the Korea Institute of Materials Science.SEN alloys are produced by adding small amounts of Ca and Y(each<1 wt%)into commercial Mg–Al based alloys,resulting in exceptional ignition and corrosion resistances and impressive mechanical properties.Their main advantages of SEN alloys are as follows.(1)A dense multi-oxide layer of SEN alloys comprising MgO,CaO,and Y_(2)O_(3) impedes the outward dispersion of Mg vapor and the inward penetration of O_(2) during oxidation,thereby enhancing the oxidation and ignition resistances.(2)The presence of Ca-and Y-based second-phase particles in SEN alloys can enhance their corrosion resistance because Ca-containing particles prevent the spread of corrosion,and the replacement of Al-containing particles with less noble ones containing Y(e.g.,Al–Mn–Y or Al–Y particles)retards corrosion.(3)The addition of minor amounts of Ca and Y renders excellent mechanical properties due to improved strengthening effects.These enhanced properties are attributed to more pronounced dynamic recrystallization and grain refining behaviors caused by the second-phase particles during extrusion.(4)Despite the presence of various types of second-phase particles,the fatigue properties of SEN9 alloys are similar to those of commercial AZ91 alloys.(5)Simultaneous introduction of Ca and Y suppresses the formation of Mg17Al12 discontinuous precipitates during aging,leading to the enhanced elongation of aged SEN alloys.(6)Adding mischmetal into the SEN9 alloy leads to a six-fold enhancement in extrudability.Consequently,the studies conducted on SEN alloys demonstrate their excellent ignition and corrosion resistances and mechanical properties,which broaden the industrial applications of Mg alloys by addressing their inherent weaknesses.

Simulation of cottonseed cake melt flow in metering zone of a single screw extruder

Research on the extrusion of natural polymers(food,feed,etc.)is relatively new due to the complex physicochemical transformations of raw materials,although plastics melt conveying and transport have been well studied.The structure and composition,rheological behavior as well as extrusion processing of natural polymer are much more complicated.In this study,a quasi-three-dimensional(3D)fluid flow model for non-Newtonian,non-isothermal and undeveloped temperature was developed,the model prediction being in reasonably good agreement with the experiment.Results show that the influence of moisture content,among other process variables,is the most significant,followed by screw speed.Some interaction exists between these two variables and the screw speed effect becomes marginal at high moisture contents.In addition,viscosity change in the channel was studied.

Preparation and Characterization of Thermoplastic Starch from Sugar Palm (Arenga pinnata) by Extrusion Method

Sugar palm(Arenga pinnata)starch is considered an important renewable,biodegradable,and eco-friendly polymer,which is derived from agricultural by-products and residues,with great potential for the development of biocomposite materials.This research was aimed at investigating the development of TPS biocomposites from A.pinnata palm starch using an extrusion process.Palm starch,glycerol,and stearic acid were extruded in a twin-screw extruder.Scanning electron microscopy(SEM)analysis of TPS showed that the starch granules were damaged and gelatinized in the extrusion process.The density of TPS was 1.3695 g/mL,lower than that of palm starch,and the addition of stearic acid resulted in increased TPS density.X-ray diffraction(XRD)results showed that palm starch had a C-type pattern crystalline structure.The tensile strength,elongation at break,and modulus of elasticity of TPS were 7.19 MPa,33.95%,and 0.56 GPa,respectively.The addition of stearic acid reduced the tensile strength,elongation at break and modulus of elasticity of TPS.The rheological properties,i.e.,melt flow rate(MFR)and viscosity of TPS,were 7.13 g/10 min and 2482.19 Pa.s,respectively.The presence of stearic acid in TPS resulted in increased MFR and decreased viscosity values.The peak gelatinization temperature of A.pinnata palm starch was 70°C,while Tg of TPS was 65°C.The addition of stearic acid reduced the Tg of TPS.The thermogravimetric analysis(TGA)analysis showed that the addition of glycerol and stearic acid decreased the thermal stability,but extended the temperature range of thermal degradation.TPS derived from A.pinnata palm starch by extrusion method has the potential to be applied in industrial practice as a promising raw material for manufacturing bio-based packaging as a sustainable and green alternative to petroleum-based plastics.

The roles of stress state and pre-straining on Swift effect for an extruded AZ31 Mg alloy

The Swift effect of Mg alloy is sensitive to initial texture.However,dislocation slip is the main deformation mechanism during torsion of Mg alloy.The underlying relation of Swift effect and dislocation slip is still not clarified.The effect of stress state and pre-straining on Swift effect was studied experimentally during free-end torsion for an extruded AZ31 alloy.The free-end torsion was performed with axial tension and compression stress which is lower than yield stress.It is found that the transition of axial deformation from contraction to elongation occurs when the axial stress changes from negative to positive.The pre-dislocations introduced by pre-tension promote axial shortening during torsion.While the pre-twins introduced by pre-compression are inhibition of axial shortening.The change of axial deformation is attributed to competition between twinning and prismatic slip.The axial shortening of extruded Mg alloy is generated by tensile twinning leading to c-axis strain.In contrast,the axial elongation can be generated by the activation of prismatic slip.The magnitude of axial strain generated by twinning is larger than that by prismatic slip.Moreover,the occurrence of detwinning results in axial elongation at low shear strain.

Numerical study on mixing performance of screw elements in intermeshing counter-rotating and co-rotating twin-screw extrudes

The flow process of unplasticized polyvinyl chloride （U PVC） through the mixing zone of intermeshing counter rotating and co rotating twin screw extruders （TSEs） were numerically simula ted by the finite element method. Three dimensional isothermal flow field of U-PVC in two kinds of TSE was calculated. The mixing performance of the screw elements of the extruders was statistically analyzed by particle tracking method. The dispersive mixing performance was characterized by the mixing index, the logarithm of stretching, and the segregation scale. The distributive mixing per forulance was characterized by the resident time distribution. The results indicate that the counter rotating TSE can build higher pressure and generate higher axial velocity and shear rate, whereas the co rotating TSE has better performance in dispersive and distributive mixing.

Hot melt extrusion:An industrially feasible approach for casting orodispersible film

Over the recent few decades,many groups of formulation scientists are concentrating on rapid release dosage forms in oral cavity.Among all fast release dosage forms,orodispersible films are successful to attract pharmaceutical industry due to ease of formulation and extension patent life.Films are popular in patients too because of quick onset and user friendliness of dosage form.From the beginning,solvent casting has been selected as method of choice for manufacturing of orodispersible films.Solvent casting has been proved as a benchmark technology because of ease in product development,process optimization,process validation and technology transfer to production scale despite of some drawbacks like more number of unit operations involved and consumption of large quantity of solvents with controlled limits of organic volatile impurities in final formulation.The application of hot-melt extrusion(HME)in the pharmaceutical industry is consecutively increasing due to its proven innumerable advantages like solvent free continuous process with fewer unit operations and better content uniformity.Very few development activities has been initiated in the field of hot melt extruded orodispersible films so far.This extensive review covers detailed discussion of heavy duty industrial extruders,selection of downstream equipments,selection of excipients,common problems found in formulations and their remedies.Successive part of review addresses identification of critical quality attributes,quality target profile of product,criticality in selection of process parameters and material for substantial simulation in laboratory scale and production for successful technology transfer.

Experimental Study of Integration and Polyblends Performance for Improved Mixing-Extruding Machine

One improved mixing-extruding machine was introduced as the second-generation product of the mixing-molding integrated technology. In the extruding system,the conventional single screw extruder was substituted by a special conical twin-screw extruder,resulting in stronger feeding ability,more stable extrusion pressure,and better quality of products. The integrated mathematical model of mixing-extruding process was also established by theoretical derivation and optimization according to the experimental results.Then its accuracy was verified by the influences of the pressure of floating weight and the cooling water temperature of extruder on the mixing-extruding integrated process. The results showed that the changes of both parameters could give rise to the fluctuation of the temperature and apparent viscosity of polyblends, thus further influencing the screw rotation speed.

3D-Printed PLA Filaments Reinforced with Nanofibrillated Cellulose

In the current study poly(lactic acid)PLA composites with a 3 wt%and 5 wt%of nanofibrillated cellulose(NFC)were produced by 3D-printing method.An enzymatic pretreatment coupled with mechanical fibrillation in a twin screw extruder was used to produce high consistency NFC.Scanning electron microscopy(SEM)equipped with Fibermetric software,FASEP fiber length distribution analysis,Furrier transform infrared spectroscopy(FT-IR),thermogravimetric analysis(TGA),tensile tests,impact tests and differential scanning calorimetry were used to characterize NFC and PLA/NFC composites.The results of the fiber length and width measurements together with the results of the SEM analysis showed that enzymatic hydrolysis coupled with a twin screw extrusion could effectively reduce the diameter and length of cellulose fibers.The produced NFC consisted of microand nanosized fibers entangled in a characteristic 3D-network.Based on the FT-IR analysis,no new bonds were formed during the enzymatic hydrolysis or fibrillation process.The TGA analysis confirmed that produced NFC can be used in hightemperature extrusion processing without NFC degradation.During the PLA/NFC composites preparation the NFC agglomerates were formed,which negatively influenced PLA/NFC composites impact properties.The slightly improved tensile strength and elastic modulus were reported for all composites when compared to the neat PLA.The elongation at break was not affected by the NFC addition.No significant differences in thermal stability were detectable among composites nor in comparation with the neat PLA.However,the crystallinity degree of the composite containing 5 wt%NFC was increased in respect to the neat PLA.

Design and Experimental Evaluation of a Spiral Feeding Device Based on Friction Characteristics of Wheat Straw

The aims of this study were to achieve working stability and continuity of the straw fibre extruder(D200)to improve the transportation efficiency of pretreated straw materials mulch film.Based on a theoretical analysis of wheat straw friction characteristics and the mechanics model of wheat straw transport,a tilting variable-diameter spiral feeding device matched the designed straw fibre extruder(D200-type).Experimental researches were performed by using the orthogonal test method of the L16(45)to obtain the optimal parameter combination.The spiral angle,the speed of the screw shaft and the moisture content of straw raw materials were selected as influencing factors,and feeding efficiency was selected as the objective indicator.The results showed that the spiral angle,the rotating speed of screw shaft and the moisture content of straw raw materials had very significant effects on the feeding efficiency(p<0.01).The order of the extent of the influence of parameters on the feeding efficiency of wheat straw raw materials from high to low was the moisture content,the spiral angle and the speed of screw shaft.When the maximum transfer efficiency per unit time of the inclined spiral feeding device was 1040.8 kg·h-1,the spiral angle was 40?,the speed of screw shaft was 200 r·min-1 and the moisture content was 65%.Verification experiment proved the feasibility of straw fibre extruder designed.

Refueling for Steady-State Plasma by Repetitive Pellet Injection in Large Helical Device

A repetitive pellet injector has been developed for investigation ofrefueling issues towards the steady-state operation in Large Helical Device (LHD). Continuousoperation of more than 10000 pellet launching at 10 Hz has been demonstrated. The maximum repeatingrate is 11 Hz. No technical constraint for longer operation has been found. The reliability ofpellet launch has exceeded 99.9%. The initial application to the NBI-heated plasmas has beensuccessful in the last experimental campaign of LHD. Although the pulse length is limited by theoperational constraint of NBI, the plasma with a density of 8 X 10^(19) m^(-3) has been sustainedfor 2 s by the pellet injection at 10 Hz. A prospect for the future experiment is discussed on thebasis of the initial result.

在VISUAL LISP环境下圆柱状螺旋弹簧建模的实现

在AUTOCAD的实际应用中,使用常用工具圆柱状螺旋弹簧的建模很难实现,甚至根本无法完成.为了解决这个问题,本文通过编制VISUAL LISP程序来实现.这样,在AUTOCAD环境下该程序不仅可以完成圆柱状螺旋线自动绘图,简化建模的过程,也可以完成使用常用工具建模所不能实现的模型.

Modification and Development of a Blow Molding Machine

This study is based on the modification and development of a two-liter plastic container blow molding machine into a five-liter one provided with a translucent view stripe. This study considers some objectives including reducing the total cost, increasing the amount of plastic recovery, and raising the desired plastic materials. Proper designs were prepared and directly applied on spot. Tangible results were obtained. Among others, the modification of some components of the machine, e.g. the extruder, has led to the possible reuse of the milled (recovery) and extra material from the manufacturing processes. That was also conducive to an effective reduction in the cost of production to 50% in some cases. Prior to its modification, this old machine was used to produce polyvinyl chloride (PVC) containers that have become prohibited these days for their damaging effect on man’s life. For now, and after modification, it has become possible to use High Density Polyethylene (HDPE) material, a fact that has improved labor conditions, too.

Low cycle fatigue behavior of the extruded AZ80 magnesium alloy under different strain amplitudes and strain rates

Low cycle fatigue behavior of extruded AZ80 magnesium alloy was investigated under uniaxial tension-compression at different strain amplitudes and strain rates.The results show that the extruded AZ80 magnesium alloy exhibits cyclic hardening at strain amplitudes ranging from 0.4%to 1.0%,the asymmetry of hysteresis loops becomes increasingly obvious when the strain amplitude increases.Higher strain rates correspond to higher stress amplitudes,high mean stresses and short fatigue life.{10–12}extension twins play a role in the cyclic deformation under higher strain amplitudes(0.8%,1.0%).The relationship between total strain energy density and fatigue life can be described by the modified Morrow model.The effect of strain rate on the fatigue life can also be predicted by the model.