Publicação
Improved methodologies for the design of extrusion forming tools
| Resumo: | Thermoplastic profiles cover a wide range of applications (window frames, structural components, vehicle door seals, medical catheters, etc.). The inherent design freedom promoted by the employment of thermoplastic profiles is one of the major reasons for their attractiveness. In the current market situation, extrusion industries aim for competitive advantages by delivering quality products within a short time. In order to produce any specific thermoplastic profile, a considerable amount of time is spent on the design of the required extrusion forming tools (namely, the extrusion die and the calibration/cooling system) since this task is usually carried out based on experimental trial-and-error procedures. This approach is highly dependent on the experience of the persons involved and usually requires high consumption of resources. Often, these limitations either inhibit the achievement of an optimal solution or increase significantly the development costs and, consequently, the final price of the produced profiles. As a major consequence, even with obvious advantages in terms of performance, the employment of thermoplastic profiles is still restricted. Obviously, these difficulties are more evident when the new profile to be produced comprises a complex geometry and there is lack of previous experience with similar products. Numerical tools, on the other hand, can provide an alternative route to design/optimize the extrusion forming tools. Even though, most of the profile extrusion forming tool designers prefer to follow the time consuming experimental trial-and-error approach, because of the cost involved in acquiring commercial modeling tools and the lack of knowledge/experience in numerical modeling. The main objective of this PhD project is to establish new and improved design procedures for the extrusion forming tools. These procedures are implemented with the aid of free/open source softwares that can attract the interest of profile extrusion industries. A new die design methodology was proposed along with the development of a solver to model the polymer melt flow inside the extrusion die. The numerical code is developed within the OpenFOAM framework, and verified for proper implementation. The proposed design methodology was used to solve two industrial case studies, proposed by a profile extrusion company. An innovative die design methodology was developed to provide simplified guidelines for the design of complex profile extrusion dies, which can be decomposed in L and T elementary geometries. The methodology is based on surrogate models, its application does not rely on any numerical tools, and it was developed mainly for designers with no access to computational modelling tools. The efficiency of the methodology was proved by assessing it with some illustrative case studies. The range of application of the simplified die design methodology was further enlarged by taking into account the processing and rheological features of the flowing polymeric material. Here, the Power-Law index ‘n’, which has the most influence on the flow distribution, was included in the model. Again, the improved methodology was assessed with complex geometries made of L and T shaped profiles, and proved to be valid for typical thermoplastic polymers. Regarding the calibration system, a numerical code, developed in the OpenFOAM framework to model the heat transfer occurring during the extrusion profile cooling process, was validated with experimental data. A study based on numerical trial-anderror approach was used to illustrate the usefulness of applying numerical tools to aid the design of the calibration systems, and a better alternative for an industrial calibration system was proposed. The work was undertaken in close cooperation with Soprefa, a Portuguese company that has been working for more than two decades in the design and production of extruded thermoplastic profiles. The developed/proposed design methodologies for extrusion forming tools were evaluated in their premises, with case studies proposed by them. |
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| Autores principais: | Rajkumar, Ananth |
| Assunto: | Extrusion forming tools thermoplastic profile complex geometry Extrusion die design Calibration system design numerical modelling OpenFOAM ferramentas de processamento por extrusão termoplásticos extrudidos geometria complexa cabeças de extrusão sistema de calibração ferramentas numéricas |
| Ano: | 2017 |
| País: | Portugal |
| Tipo de documento: | tese de doutoramento |
| Tipo de acesso: | acesso aberto |
| Instituição associada: | Universidade do Minho |
| Idioma: | português |
| Origem: | RepositóriUM - Universidade do Minho |
| Resumo: | Thermoplastic profiles cover a wide range of applications (window frames, structural components, vehicle door seals, medical catheters, etc.). The inherent design freedom promoted by the employment of thermoplastic profiles is one of the major reasons for their attractiveness. In the current market situation, extrusion industries aim for competitive advantages by delivering quality products within a short time. In order to produce any specific thermoplastic profile, a considerable amount of time is spent on the design of the required extrusion forming tools (namely, the extrusion die and the calibration/cooling system) since this task is usually carried out based on experimental trial-and-error procedures. This approach is highly dependent on the experience of the persons involved and usually requires high consumption of resources. Often, these limitations either inhibit the achievement of an optimal solution or increase significantly the development costs and, consequently, the final price of the produced profiles. As a major consequence, even with obvious advantages in terms of performance, the employment of thermoplastic profiles is still restricted. Obviously, these difficulties are more evident when the new profile to be produced comprises a complex geometry and there is lack of previous experience with similar products. Numerical tools, on the other hand, can provide an alternative route to design/optimize the extrusion forming tools. Even though, most of the profile extrusion forming tool designers prefer to follow the time consuming experimental trial-and-error approach, because of the cost involved in acquiring commercial modeling tools and the lack of knowledge/experience in numerical modeling. The main objective of this PhD project is to establish new and improved design procedures for the extrusion forming tools. These procedures are implemented with the aid of free/open source softwares that can attract the interest of profile extrusion industries. A new die design methodology was proposed along with the development of a solver to model the polymer melt flow inside the extrusion die. The numerical code is developed within the OpenFOAM framework, and verified for proper implementation. The proposed design methodology was used to solve two industrial case studies, proposed by a profile extrusion company. An innovative die design methodology was developed to provide simplified guidelines for the design of complex profile extrusion dies, which can be decomposed in L and T elementary geometries. The methodology is based on surrogate models, its application does not rely on any numerical tools, and it was developed mainly for designers with no access to computational modelling tools. The efficiency of the methodology was proved by assessing it with some illustrative case studies. The range of application of the simplified die design methodology was further enlarged by taking into account the processing and rheological features of the flowing polymeric material. Here, the Power-Law index ‘n’, which has the most influence on the flow distribution, was included in the model. Again, the improved methodology was assessed with complex geometries made of L and T shaped profiles, and proved to be valid for typical thermoplastic polymers. Regarding the calibration system, a numerical code, developed in the OpenFOAM framework to model the heat transfer occurring during the extrusion profile cooling process, was validated with experimental data. A study based on numerical trial-anderror approach was used to illustrate the usefulness of applying numerical tools to aid the design of the calibration systems, and a better alternative for an industrial calibration system was proposed. The work was undertaken in close cooperation with Soprefa, a Portuguese company that has been working for more than two decades in the design and production of extruded thermoplastic profiles. The developed/proposed design methodologies for extrusion forming tools were evaluated in their premises, with case studies proposed by them. |
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