Publicação
Numerical modelling of the filling stage of the injection moulding process
| Resumo: | The increased demand for plastic materials promoted an increase in the requirements of various transformation processes, namely injection moulding, which is nowadays the most used transformation process for the manufacture of plastic material parts. This transformation technique presents the return of investment in the medium / long term and a wide range of geometries that can be produced. It is a process that has a high fixed cost not only due to the moulds used, but also due to the many process variables that are necessary to control and optimize to achieve the optimal processing conditions. It is exactly due to this type of requirements that the simulation started to gain more importance, being nowadays an indispensable step in the design phase, either in the control of the process variables or in the optimization of the same, to reach high levels of effectiveness. This work deals with aspects related to the numerical modelling of the thermoplastic injection moulding process, and its main objectives were the validation of an open-source solver developed for the simulation of the injection moulding process, and, the creation of a successful case study that could be replicated experimentally. The main motivation for this is due to the fact that there are not any codes in the free distribution software market capable of simulating the injection moulding process with the desired precision characteristics, and with calculation times appropriate to the industrial production pace. Firstly, this work aimed to identify the equations that govern the different phases of the injection moulding process, and the numerical methods used in numerical modelling codes. In this context, the constitutive models suitable for plastic materials were also studied. Then, using several case studies, validation tests were carried out using the open-source solver named, openInjMoldSim, which is based on the OpenFOAM® computational library. In a first step, it was found that the velocity and pressure profiles predicted by the solver were similar to those obtained with analytical solutions. In the second case, two formulations of equation of state were used, one compressible and the other incompressible. The results obtained allowed to conclude that the incompressible formulation reduce the calculation time and improve the stability of the numerical process, without any significant loss of accuracy. Finally, a comparison study was carried out between the open-source solver and the commercial software Moldex3D®. From this study, we concluded that for the same precision, and not having full knowledge of the equations and calculation methods used in commercial software, Moldex3D® was 10 times faster than OpenFOAM®, when using the same number of cores in the computation. Moreover, when taking full advantage of the parallelization capabilities of OpenFOAM®, the calculation time was the same in both softwares. |
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| Autores principais: | Pedro, João Luís Oliveira |
| Assunto: | Equation of state Filling stage Injection Moulding Process Moldex3D® Numerical Modelling OpenFOAM® Equação de estado Fase de injeção Modelação numérica Moldação por injeção |
| Ano: | 2020 |
| País: | Portugal |
| Tipo de documento: | dissertação de mestrado |
| Tipo de acesso: | acesso aberto |
| Instituição associada: | Universidade do Minho |
| Idioma: | inglês |
| Origem: | RepositóriUM - Universidade do Minho |
| Resumo: | The increased demand for plastic materials promoted an increase in the requirements of various transformation processes, namely injection moulding, which is nowadays the most used transformation process for the manufacture of plastic material parts. This transformation technique presents the return of investment in the medium / long term and a wide range of geometries that can be produced. It is a process that has a high fixed cost not only due to the moulds used, but also due to the many process variables that are necessary to control and optimize to achieve the optimal processing conditions. It is exactly due to this type of requirements that the simulation started to gain more importance, being nowadays an indispensable step in the design phase, either in the control of the process variables or in the optimization of the same, to reach high levels of effectiveness. This work deals with aspects related to the numerical modelling of the thermoplastic injection moulding process, and its main objectives were the validation of an open-source solver developed for the simulation of the injection moulding process, and, the creation of a successful case study that could be replicated experimentally. The main motivation for this is due to the fact that there are not any codes in the free distribution software market capable of simulating the injection moulding process with the desired precision characteristics, and with calculation times appropriate to the industrial production pace. Firstly, this work aimed to identify the equations that govern the different phases of the injection moulding process, and the numerical methods used in numerical modelling codes. In this context, the constitutive models suitable for plastic materials were also studied. Then, using several case studies, validation tests were carried out using the open-source solver named, openInjMoldSim, which is based on the OpenFOAM® computational library. In a first step, it was found that the velocity and pressure profiles predicted by the solver were similar to those obtained with analytical solutions. In the second case, two formulations of equation of state were used, one compressible and the other incompressible. The results obtained allowed to conclude that the incompressible formulation reduce the calculation time and improve the stability of the numerical process, without any significant loss of accuracy. Finally, a comparison study was carried out between the open-source solver and the commercial software Moldex3D®. From this study, we concluded that for the same precision, and not having full knowledge of the equations and calculation methods used in commercial software, Moldex3D® was 10 times faster than OpenFOAM®, when using the same number of cores in the computation. Moreover, when taking full advantage of the parallelization capabilities of OpenFOAM®, the calculation time was the same in both softwares. |
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