bluuebunny/crossref_metadata_2025_split huggingface dataset:
Evaluation of a Model Describing the Advancing Flow Front in Injection Moulding
Authors: Pisciotti F. , Boldizar A. , Rigdahl M. , Aronsson G. 
Published: December 2013

Abstract
The simulation of the advancing flow front during mould filling in the injection moulding cycle is important as a way of anticipating manufacturing defects, particularly different types of welds, air traps, cold spots and hot spots. The purpose of the present work was to evaluate a model (the distance model) simulating the advancing flow front and predicting potential issues related to the progression of the flow front such as welds and air traps. The distance model is based on a mathematical theory of Hele-Shaw flow for strongly shear-thinning fluids, i. e. fluids with a power-law index, n, equal to 0,3 or preferably less. Two grades of general-purpose polystyrene were selected according to their abilities to shear thin (weakly or moderately strong) at the selected processing temperature and in the typical shear rate range of the injection moulding process. The two grades were injection moulded into twelve mould configurations derived from two similar single-gated moulds. The flow length from the gate to the weld was measured in the mouldings obtained at three distinct rates of filling (conventional, slower and faster) and compared to the flow lengths obtained by the distance model. Good agreement was found between the predicted flow lengths and the experimental flow lengths at the conventional and faster filling conditions. Larger deviations between simulation and experiment were found at the slower filling rate, particularly for the weakly shear-thinning polystyrene grade. Some comparisons were also made with the predictions obtained using the commercial simulation code Moldflow. A comparison between the advancing front predictions of the distance model and experimental short shots of a commercial polypropylene grade in a lure-box type of mould geometry showed that the distance model, despite its simplicity, could probably be used to detect welds and air traps in more complex and practice-related mouldings.
Analysis of Heat Flu from Molten Polymers to Molds in Injection Molding Processes
Authors: Shiraishi Y. , Norikane H. , Narazaki N. , Kikutani T. 
Published: December 2013

Abstract
The inverse analysis method is applied in the evaluation of heat flux at the interface between the molten polymer and the mold during the injection molding process. In addition, the dependence of cooling behavior on both the molding conditions and the material properties of the resin are investigated. During low-velocity polymer flow in the thick regions of the mold cavity, the heat flux in the later stage of the process evaluated through experiment correlates well with the theoretical results of equations describing heat conduction at the interface of two semi-infinite objects. In contrast, in the thin region of the mold cavity, the analyzed heat flux is greater than the theoretical result for high-velocity polymer flow, and the difference expands with an increase in the shear rate at the wall of the mold. Based on these results, a simple empirical equation applicable to a wide range of molding conditions is proposed for the estimation of heat flux at the polymer-mold interface.
Process Design for Reducing the Warpage in Thin-walled Injection Molding
Authors: Wang T.-H. , Young W.-B. , Wang J. 
Published: December 2013

Abstract
The process design of the thin-walled injection molding is investigated in this study. It was realized that the behavior of warpage in injection molding parts was affected by different process conditions such as melt temperature, mold temperature, packing pressure and injection rate. Experimental design of Taguchi method was used to determine the process conditions. Both the numerical simulations and experiments were conducted to study the effects of the process conditions on the warpage of a cap model. The proper processing parameters were also identified by the experimental design. The packing pressure was found to be the most important factor on the warpage of a thin-walled part. The experimental design done by numerical simulations also provided proper results in terms of warpage reduction.
Optimization of Processing Conditions for Polymer Twin-Screw Extrusion
Authors: Gaspar-Cunha A. , Poulesquen A. , Vergnes B. , Covas J. A. 
Published: December 2013

Abstract
The problem of setting the best operating conditions of a co-rotating twin-screw extruder is solved using an optimization approach based on Genetic Algorithms. Two possibilities are considered: i) the maximization of an objective function; ii) the simultaneous optimization of the individual criteria and the use of Pareto plots. The flow conditions inside the machine are simulated using the Ludovic© software. Various practical case studies are discussed, among them a reactive extrusion application. Generally, the methodology is sensitive to the influence of the main process criteria and provides solutions that are apparently sound.
The Role of Tool/Sheet Contact in Plug-assisted Thermoforming
Authors: Collins P. , Harkin-Jones E. M. A. , Martin P. J. 
Published: December 2013

Abstract
Plug-assisted thermoforming produces a wide range of polymer products through a combination of deformation by air pressure and contact with tool surfaces. In this paper the role of tool/sheet contact in determining the process output is investigated. A combination of thermoforming, friction and heat transfer tests were carried out on common tool and sheet materials. The results show that the typical friction coefficients for the material combinations are within the range 0.1 to 0.3, but the values rise sharply on approaching thermoforming temperatures. Thermal imaging tests demonstrate that all of the plug materials significantly cool the heated sheet on contact, even over very short periods of time. The temperature of the plug is very important. At low plug temperatures heat transfer effects predominate, whereas at high plug temperatures friction effects predominate. A plug temperature of approximately 100°C balances these effects and creates the most effective material distribution.
Effect of Processing History on the Sintering of Ethylene Copolymers
Authors: Guillén-Castellanos S. A. , Lin W. , Bellehumeur C. T. , Weber M. 
Published: December 2013

Abstract
Polymer sintering plays a major role in processes such as rotational molding, governing the heating cycle and the properties of the final parts. There is evidence to suggest that the material molecular structure, molecular order and morphology are of importance in the sintering process. To date, however, there has been no satisfactory explanation as for their role in polymer sintering. One objective of this work is to examine the sintering behavior of ethylene copolymers under conditions related to the rotational molding process and to determine the relative effects of the polymer molecular structure and morphology on the sintering process. Sintering experiments were conducted under isothermal and non-isothermal conditions using both powder and cylindrical particles. It was found that the trends observed for the sintering of powder were consistent with the predictions of Newtonian sintering models. Sintering results obtained using cylindrical particles, however, showed significant differences not seen when using powder particles. These were attributed to the differences in the surface area between the two types of particles. It is speculated that the effect of material properties other than viscosity and elasticity are enhanced when cylindrical particles are used.
Five Geometric Principles for Injection Molding
Authors: Aronsson G. 
Published: December 2013

Abstract
A condensed presentation of some results of a geometric character, concerning the injection molding of plastics, is given here. The author has derived these results from mathematical arguments and some simplifying assumptions, besides the usual Hele-Shaw flow conditions.
The presentation here is intended for readers with an interest in polymer processing, rather than mathematics, so that the mathematical derivations are omitted in some cases, and sketchy in other cases. Instead we try to explain the results using figures, intuitive arguments and a few inevitable formulas. Since the experimental verification of the results is still very incomplete, we prefer to present them as proposed principles. Comments and suggestions for improvement are very welcome.
Modelling of Residual Stresses and Warpage in Sandwich Injection Moulding
Authors: Lundström T. S. , Toll S. 
Published: December 2013

Abstract
Sandwich injection moulding offers the possibility of combining materials with different properties and, for instance, hide a recycled constituent within a virgin ditto. This attractive potential puts great demands on the manufacturing and therefore also on the process modelling. In particular the effect on the final stress state and the deformation of the part due to the heterogeneity of the material must be clarified. This topic is addressed in this study. To start with it is confirmed that expressions for the temperature field can be much simplified without major loss of accuracy in the solution. This enables us to take an analytical approach to the modelling and the resulting equations can be solved on a spread-sheet or with a simple code. It is also shown that the derived models compare well to experiments made with a two-layered structure, indicating that the models presented can be used to estimate changes of processing conditions or material properties for sandwich structures.
Analysis and Optimization of Kenics Static Mixers
Authors: Galaktionov O. S. , Anderson P. D. , Peters G. W. M. , Meijer H. E. H. 
Published: December 2013

Abstract
The mapping approach is applied to study the distributive mixing in the, widely industrially used, Kenics static mixer. The flexibility of the mapping method makes it possible to study and compare thousands of different mixer layouts and perform optimization with respect to macroscopic homogenization efficiency and interface generation. In the paper two different designs of the mixer are investigated. The conventional mixer with sequentially different twisted blades and adesign where the twist direction is maintained constant. In both cases the blade twist angle is varied. Recommendations are given in the choice of the design of the mixer dependent on the desired structure of mixing.
Flexible Sheet Molding Compound (SMC) Using Aliphatic Polyester as Cross Linker
Authors: Esfandeh M. , Ebrahimi M. R. 
Published: December 2013

Abstract
Thermoset resins are brittle and have a poor resistance to crack initiation and growth. This is attributed to their amorphous and highly cross-linked structure. In composite parts made from thermoset molding compositions such as Sheet Molding Compound (SMC) and Bulk Molding Compound (BMC), the initial stage of composite failure is attributed to the properties of the polyester based resin. Thus, improving resin properties by adding various additives has been an interesting area of research. In this work, Maleic anhydride-terminated polycaprolactone (MATPCL) was used to modify the flexural properties of unsaturated polyester (UP) resin. MATPCL was prepared in the lab and was added to UP at 3, 5, 10, 20, 40 and 50 percent by weight. Mechanical properties of the cured samples (flexural and impact strength) were determined and an almost linear increase in impact properties was observed with increasing the MATPCL content. Phase behavior of UP/MATPCL blends was inspected both visually and using scanning electron microscopy and, no gross phase separation was seen at the levels used. SMC was prepared in conventional method using chopped glass fibers and the resin formulation having 20 wt% of MATPCL. Thickening behavior, molding characteristics, mechanical properties and fracture behavior of the prepared sheets were determined and compared with the sheets made from non-modified UP resin.
Neural Network Approach to Density Control of Rigid PVC Foam in Extrusion Process
Authors: Abu-Zahra N. H. 
Published: December 2013

Abstract
In rigid PVC foam extrusion, foam density is very crucial in determining the mechanical characteristics of the extruded material and the profitability of the manufacturing process. This paper presents a new application of artificial neural computing in the control of PVC foam density in profile extrusion process. A 3-layer multi-layer perceptron (MLP) artificial neural network was developed to estimate the foam density (weight) based on the known processing conditions; mainly heating zones temperatures and screw speed. The network was developed and tested on a specific formula that is used in wood-like products. A two factorial design of experiment was carried out to determine the significant process variables before training the neural networks using a back propagation algorithm. Finally, a comparison between the true weights, and the estimated weights using artificial neural networks is presented.
A Dynamic Model Accounting for Oscillating Behavior in Reactive Extrusion
Authors: Janssen L. P. B. M. , Rozendal P. F. , Hoogstraten H. W. , Cioffi M. 
Published: December 2013

Abstract
A qualitative mathematical model on the oscillating behavior of reactive extrusion is presented. Through the introduction of stagnant volume build up in the die as a result of the ongoing reactive extrusion process, a variable time dependent die resistance emerges. A differential equation for the waxing and waning of stagnant volume in the die is developed. This equation is able to give oscillating behavior for certain extruder parameters and viscosity when coupled to an existing dynamic model of the fully-filled length. The effects of reaction rate, rotational speed, feed rate, die resistance and degree-of-fill are studied.
On the Residual Stress and Shrinkage in Injection Compression Molding
Authors: Young W.-B. 
Published: December 2013

Abstract
Injection compression molding is a process having a compression action in the filling or postfilling stages. This process is suitable for molding of parts with precision features. The success of an injection compression molding process relies on proper design of the mold and selection of process conditions. The main scope of this study is to develop an analysis tool for the residual stresses and shrinkage of an injection compression molding process. A simple thermoviscoelastic model was used to calculate the stress and relaxation developed in the postfilling stage. The model divides the thickness into two regions, glassy and rubbery phases. Residual stress calculation is applied in the glassy region, while the rubbery region is kept at the melt pressure without any strain because of the fast relaxation in this region. The resulted in-mold stress fields are used to calculate the part shrinkage after demolding. The effects of the compression force on the residual stresses and shrinkage of a molding part were also investigated. Higher compression force tends to reduce the part shrinkage but induces a higher level of residual stresses.
Prediction of Residence Time Distribution in EZ and KE Element of a Ko-Kneader by using CFD Method
Authors: Mehranpour M. , Nazokdast H. , Dabir B. 
Published: December 2013

Abstract
Residence time distribution is among the important parameters of the Buss Ko-Kneader which allows one to better understand the flow conditions inside the system and to get information on mixing efficiency. However it has always been a difficult task to predict the RTD of complex geometries such as Buss elements.
The aim of the present work was to estimate the residence time distribution in EZ and KE element of the Buss Ko-Kneader by utilizing an elemental tracing method performed on the flow fields in the same elements which were analysized by CFD method. The effects of rotating and reciprocating motions of the screw have been taken into account in three dimensional flow analysis. It was demonstrated that these results can provide valuable information on mixing performance of these two elements.
Prediction of Residence Time Distribution for Different Screw Configurations of a Ko-Kneader by using a Cluster Model
Authors: Mehranpour M. , Nazokdast H. , Dabir B. 
Published: December 2013

Abstract
Prediction of residence time distribution (RTD) in the modular type screw extruders has always been one of the most attractive subjects for predicting. In the present work an attempt was made to establish a method with functionality similar to additive rule for predicting RTD of the modular screw extruders with different configurations such as Buss Ko-Kneader. Results predicted from this method, which was named as cluster model, were compared with the results predicted based on our previously reported trajectory method as well as experimental results. A reasonability good agreement was found between these results justified reliability of the cluster model for being used as a new approach to predict the RTD of the modular screw extruders.
Measuring Polymer Melt Density and Viscosity in Real-time during Extrusion Processes using Ultrasound Sensors Fusion
Authors: Abu-Zahra N. H. 
Published: December 2013

Abstract
A dual-sensor system is developed to measure the density and viscosity of polymer melts, simultaneously, during extrusion process. The sensory system utilizes a 2.25 MHz longitudinal ultrasound transducer in conjunction with a 2.25 MHz shear type ultrasound transducer, placed in a modified extrusion die. The acoustic impedance of the polymer melt, corresponding to the longitudinal ultrasound waves (UTL), is used to measure the density of the polymer melt using established physical models. While, the acoustic impedance of the shear waves (UTS) is used to measure the viscosity of the polymer melt, utilizing the density measurements obtained by the longitudinal ultrasound transducer.
The system was evaluated using polyvinyl chloride compounds containing various levels of foaming agent and processing aid at fixed processing conditions. The system measurements of the melt density was compared to the density of the extrudate, while the viscosity measurements were compared to the calculated values using slit-rheometry equations. The correlation coefficients between the ultrasound sensor and actual measurements were in the range of 92% and 96% for the melt density and viscosity; respectively.
Analysis of the Morphological Development of PBT/ABS Blends during the Twin Screw Extrusion and Injection Molding Processes
Authors: Ito E. N. , Pessan L. A. , Covas J. A. , Hage E. 
Published: December 2013

Abstract
The aim of this work was to observe the development of the phase morphology of the PBT/ABS blends during their extrusion mixing and injection molding steps. The evolution of the blend morphology during the mixing stage was analyzed using a specially designed co-rotational twin-screw extruder with a collecting device located along the barrel. Blend samples were collected in-line along the length of the extruder barrel during the blending process. Samples obtained from the extruded pellets and from injection molded specimens were also used to observe the blend morphology. All the samples were observed by transmission electron microscopy (TEM). They were prepared by cryo-ultramicrotomy and the rubbery phase of the ABS contained in the blends was stained with osmium tetroxide (OsO4). A special function was established and is proposed to analyze the blend morphology trends through image analysis. In binary blends, the ABS phase showed better dispersion after the mixture passed through the extruder die. However, a coalescence phenomenon was observed during the next molding step. Compatibilized PBT/ABS blends showed better dispersion than binary blends, even after injection molding. The special function used to quantify the dispersion throughout the mixing and molding steps showed an excellent performance.
Development of a Hybrid Solid-Microcellular Co-injection Molding Process
Authors: Turng L.-S. , Kharbas H. 
Published: December 2013

Abstract
This paper presents the development of a hybrid solid-microcellular co-injection molding process that combines aesthetic and processing advantages of injection molding with benefits and property attributes of microcellular plastics (MCPs). A two-color injection molding machine has been modified and equipped with an interfacial platen and a supercritical fluid (SCF) unit for co-injection molding with regular resins and MCPs. Co-injection molded polystyrene (PS) parts with a microcellular core encapsulated by the solid skin layer have been successfully produced. Systematic experiments were carried out with solid-microcellular co-injection molding, conventional solid-solid co-injection molding, and regular microcellular injection molding processes to study the effects of process conditions and core/skin volume ratios on the penetration and morphology of the microcellular core. Light microscopy and scanning electron microscopy (SEM) of the solid-microcellular co-injection molded specimens reveal a microcellular core with fairly fine and uniform cell size of 8 to 12 microns and a cell density of up to 3 × 10 cells/cm. Under similar process conditions, microcellular cores were found to penetrate longer and generate a more uniform and thicker skin layer than do solid cores. While improving the surface finish with solid skin layers, this process is capable of producing parts with reduced sink marks, lighter part weights, and shorter cycle times.
Novel Extrusion Dies with Rotating Rollers for CO2-Plastic Foam Production
Authors: Benkreira H. , Gale M. , Patel R. , Cox M. , Paragreen J. 
Published: December 2013

Abstract
This paper describes a new roller die design capable of generating high pressures to allow the direct injection of liquid carbon dioxide into polymer melts and produce low density foams. The novelty of the design lies in the counter-flow action of a pair of rotating rollers separated by a gap to build up pressure. A mathematical model of the flow in the extrusion-roller die system is described and tested against experimental data with PS, LDPE and PP under a wide range of roller speeds and gaps. The study shows that this new design is feasible but more comprehensive CFD simulations and experiments are required to optimise design and operation to obtain the low-density polymer foams sought.
On the Use of the Heating Stage to Control the Thickness Distribution in Thermoformed Parts
Authors: Duarte F. M. , Covas J. A. 
Published: December 2013

Abstract
This work investigates the influence of the heating stage of roll-fed and sheet-to-sheet thermoforming on the thickness uniformity of the final parts produced. Modeling of the heat transfer process involved in each case is carried out. An inverse methodology capable of setting the temperature of the heaters that produce a prescribed sheet temperature at the end of the heating stage is presented. The sensitivity of this differential heating technique to moderate perturbations of the individual set values is analyzed.