Academic literature on the topic 'Injection molding simulation'

Dissertation (Ph. D.)--University of Akron, Dept. of Polymer Engineering, 2009.<br>"May, 2009." Title from electronic dissertation title page (viewed 11/27/2009) Advisor, Avraam I. Isayev; Committee members, James L. White, Erol Sancaktar, Kevin Kreider, Minel J. Braun; Department Chair, Sadhan C. Jana; Dean of the College, Stephen Cheng; Dean of the Graduate School, George R. Newkome. Includes bibliographical references.

Um den Spritzgießprozess zu simulieren, sind korrekte Materialdaten nötig. Diese Daten umfassen Viskositätsmodelle, Wärmekapazitätskoeffizienten, Wärmeleitfähigkeitskoeffizienten, PVT-Modelle und bei reaktiven Materialien Härtungsmodelle. Bei der Spritzgießsimulation von Thermoplasten sind die Materialdaten in der Regel in den Simulationstools verfügbar. Der Anwender kann problemlos Thermoplastmaterialdaten auswählen, die bereits in die Materialdatenbank der Simulationswerkzeuge eingebettet waren, um die gesamten Phasen des Thermoplastspritzgießprozesses zu simulieren. Bei der Duroplastspritzgießsimulation sind nur begrenzt Materialdaten vorhanden und selten aus der Datenbank der Simulationswerkzeuge verfügbar, da sie nicht nur bei der Messung rheologischer und thermischer Eigenschaften, sondern auch bei der Modellierung rheologischer und kinetischer mathematischer Modelle kompliziert sind. Daher ist es notwendig, eigene Materialdaten zu generieren. Um dieses Problem zu lösen, bedarf es einer umfangreichen Wissensbasis bei der Messung von Materialeigenschaften sowie der Erstellung eines Optimierungsalgorithmus´. Um den Prozess des duroplastischen Spritzgießens exakt zu simulieren, bedarf es zudem fundierter Kenntnisse über die Formfüllungseigenschaften dieser Materialien. Die Untersuchung des Fließverhaltens von duroplastischen Spritzgießmassen im Inneren der Kavität ist jedoch nicht ausreichend beschrieben. Bisher gab es noch keine veröffentlichten Hinweise, die zeigen, wie man aus experimentellen Messdaten (thermische und rheologische Daten) für den reaktiven Spritzgießsimulationsprozess komplette Materialdaten für Duroplaste erzeugen kann. Diese Probleme führen zu einer Abhängigkeit der Anwender von der Materialdatenbank der Simulationssoftware, was zu einer Einschränkung der Anwendung der Computersimulation in der duroplastischen Spritzgießsimulation und dem Vergleich zwischen experimentellen und Simulationsergebnissen führt. Darüber hinaus stellt sich die Frage, ob es beim Füllen der Kavität ein Wandgleiten zwischen Duroplastschmelze und Wandoberfläche gibt oder nicht. Aus diesem Grund wird die Wirkung des Wandgleitens auf die Kavitätenoberfläche bei der Simulation des duroplastischen Spritzgießens immer noch vernachlässigt. Die vorliegende Arbeit konzentriert sich auf drei wichtige wissenschaftliche Ziele. Das erste ist die Innovation eines neuen technischen Verfahrens zur physikalischen Erklärung des Formfüllverhaltens von duroplastischen Spritzgießmassen. Das zweite Hauptziel ist die Entwicklung einer numerischen Methode zur Erstellung eines duroplastischen Materialdatenblattes zur Simulation der Formfüllung von duroplastischen Spritzgießmassen. Schließlich wird die Erstellung von Simulationswerkzeugen auf der Grundlage der physikalischen Gegebenheiten und des erzeugten Materialdatenblattes durchgeführt.<br>To simulate the injection molding process, it is necessary to set material data. The material data for an injection molding process must include a viscosity model and its fitted coefficients, heat capacity coefficients, thermal conductivity coefficients, a PVT model and its coefficients, a curing model and its coefficients (only for reactive injection molding). With thermoplastics injection molding simulation, the material data is generally available from simulation tools. Users could easily choose thermoplastics material data that was already embedded in the material data bank of simulation tools to simulate the entire phases of thermoplastics injection molding process. However, with thermosets injection molding simulation, the material data is found in limited sources and seldom available from data bank of simulation tools because of complication not only in rheological and thermal properties measurement but also in modeling rheological and cure kinetics mathematical models. Therefore, with thermoset injection molding compounds that its material data bank has not been found in data bank of simulation tools, before setting material data, it is necessary to create its own material data that simulation packages do not supply a tool. Therefore, to solve this problem, it requires an extensive knowledge base in measurements of material properties as well as optimization algorithm. In addition, to simulate exactly the thermosets injection molding compound process, it requires a profound knowledge in the mold filling characteristics of thermoset injection molding compounds. However, investigation of flow behavior of thermosets injection molding compounds inside the mold has not been adequately described. Up to now, there has not been any article that shows a complete way to create thermoset material data from measured experimental data (thermal data and rheological data) for the reactive injection molding simulation process. These problems are leading to the users ‘dependency on the material data bank of simulation tools, leading to restriction in application of computer simulation in the thermoset injection molding simulation and comparison between experimental and simulation results. Furthermore, there is still a big question related to whether there is or no slip phenomenon between thermosets melt and the wall surface during filling the cavity, for which has not yet been found an exact answer. Because of this the effect of wall slip on the cavity surface is still ignored during thermoset injection molding simulation process. This thesis focused on three key scientific goals. The first one is innovation of a new technical method to explain the mold filling behavior of thermoset injection molding compounds physically. The second key goal is developing numerical method to create thermoset material data sheet for simulation of mold filling characterizations of thermoset injection molding compounds. Finally, creating a simulation tool base on the physical technique and generated material data sheet.

Procédé de moulage par injection de poudres est constitué de quatre étapes principales: la préparation des matières premières, moulage par injection, le déliantage et le frittage. Cette thèse présente les recherches sur deux aspects principaux: la micro-injection et frittage par micro -ondes. Les contributions principaux peuvent être conclues dans les quatre aspects suivants: Modification et complément de l'algorithme précédent pour la simulation du procédé de moulage par injection; L'évaluation et la mise en œuvre de l'effet de tension de surface en simulation pour micro-injection; Micro-ondes expériences de frittage de compacts basés sur l'acier inoxydable 17-4PH; Réalisation de la simulation de frittage à micro-ondes avec couplage de la multi-physique, y compris le chauffage à micro-ondes classique, le transfert de chaleur, et le supplément de modèle pour la densification de frittage de la poudre compacté<br>Powder Injection molding process consists off our main stages: feedstock preparation, injection molding, debinding and sintering. The thesis presents the research on two main aspects: micro injectionmolding and microwave sintering. The main contributions can be concluded in thefollowing four aspects: Modification and supplement of previous algorithm for the simulation ofinjection molding process; Evaluation and implementation of surface tension effect in simulation for micro injection; Microwave sintering experiments of compacts based on 17-4PH stainles ssteel; Realization of the microwave sintering simulation with the coupling of multi-physics,including the classic microwave heating, heat transfer, and the supplement of model for sintering densification of powder impacts

Thesis (MTech (Mechanical Engineering))--Peninsula Technikon, 2003<br>Injection moulding is a process by which molten polymer is forced into an empty cavity of the desired shape. At its melting point, polymers undergo a volumetric expansion when heated, and volumetric contraction when cooled. This volumetric contraction is called shrinkage. Once the mould cavity is filled, more pressure is applied and additional polymer is packed into the cavity and held to compensate for the anticipated shrinkage as the polymer solidifies. The cooling takes place via the cooling channels where the polymer is cooled until a specific ejection criterion is met. Heat from the polymer is lost to the surrounding mould, a part of this heat reaches the cooling channel surfaces, which in turn exchange heat with the circulating cooling fluid. Due to the complexity of injection moulded parts and the cooling channel layout, it is difficult to achieve balanced cooling of parts. Asymmetric mould temperature distribution causes contractions of• the polymer as it cools from its melting temperature to room temperature. This results in residual stresses, which causes the part to warp after ejection. Given the understanding of the mathematical model describing the heat transfer process during the cooling stage, the objectives of this study were three fold. Firstly, an alternative numerical model for the heat transfer process was developed. The proposed model was used to investigate the cooling stress build-up during the injection moulding process.

Nowadays, the filling and solidification of macro-scale injection mouldings can be predicted using commercial CAE software. For micro-injection moulding, the conventional tools do not work for all process conditions. The reasons might be the lack of high quality database used in the simulation and the improperly specified boundary conditions which do not reflect the real state in the cavity. Special aspects like surface tension or "size dependent" viscosity might also be responsible for the inaccuracy of the simulations. In this paper, those aspects related to the boundary conditions were taken into consideration, especially the thermal contact behaviour and the melt compression in the barrel which affects not only the temperature of the melt due to the compression heating, but also reduces the actual volume rate in the cavity. It can be shown that the heat transfer coefficient between the melt and the mould wall has a significant influence on the simulation results. In combination with precise material data and considering the reduction of the volume rate due to the melt compression in the barrel, the heat transfer coefficient may be quantified by means of reverse engineering. In general, it decreases when either the cavity thickness or the injection speed increases. It is believed that a pressure dependent model for the heat transfer coefficient would be more suitable to describe the thermal contact behaviour in micro injection moulding. The melt compression in the barrel affects definitely the filling behaviour and subsequently the heat transfer in the cavity as well, which is especially true for micro parts of high aspect ratio.

Micro-Powder Injection Moulding (Micro-PIM) technology is one of the key technologies that permit to fit with the increasing demands for smaller parts associated to miniaturization and functionalization in different application fields. The thesis focuses first on the elaboration and characterization of polymer-powder mixtures based on 316L stainless steel powders, and then on the identification of physical and material parameters related to the sintering stage and to the numerical simulations of the sintering process. Mixtures formulation with new binder systems based on different polymeric components have been developed for 316L stainless steel powders (5 µm and 16 µm). The characterization of the resulting mixtures for each group is carried out using mixing torque tests and viscosity tests. The mixture associated to the formulation comprising polypropylene + paraffin wax + stearic acid is well adapted for both powders and has been retained in the subsequent tests, due to the low value of the mixing torque and shear viscosity. The critical powder volume loading with 316L stainless steel powder (5 µm) according to the retained formulation has been established to 68% using four different methods. Micro mono-material injection (with 316L stainless steel mélange) and bi-material injection (with 316L stainless steel mélange and Cu mélange) are properly investigated. Homogeneity tests are observed for mixtures before and after injection. A physical model well suited for sintering stage is proposed for the simulation of sintering stage. The identification of physical parameters associated to proposed model are defined from the sintering stages in considering 316L stainless steel (5 µm)mixtures with various powder volume loadings (62%, 64% and 66%). Beam-bending tests and free sintering tests and thermo-Mechanical-Analyses (TMA) have also investigated. Three sintering stages corresponding to heating rates at 5 °C/min, 10 °C/min and 15 °C/min are used during both beam-bending tests and free sintering tests. On basis of the results obtained from dilatometry measurements, the shear viscosity module G, the bulk viscosity module K and the sintering stress σs are identified using Matlab® software. Afterwards, the sintering model is implemented in the Abaqus® finite element code, and appropriate finite elements have been used for the support and micro-specimens, respectively. The physical material parameters resulting from the identification experiments are used to establish the proper 316L stainless steel mixture, in combination with G, K and σs parameters. Finally, the sintering stages up to 1200 °C with three heating rates (5 °C/min, 10 °C/min and 15 °C/min) are also simulated corresponding to the four micro-specimen types (powder volume loading of 62%, 64% and 66%). The simulated shrinkages and relative densities of the sintered micro-specimens are compared to the experimental results indicating a proper agreement