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2020Author
Tromm, MikeSubject
600 Technology 660 Chemical engineering SpritzgießenSchaumkunststoffMechanische EigenschaftProzessentwicklung <Technik>WerkzeugLeichtbauChemische StrukturMetadata
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Controlling cellular structure in thermoplastic foam injection molding – influence of processing and mold technologies
Abstract
Foam injection molding is a processing technology to produce foamed plastic parts in serials production, attaining an increasing interest and use in industry. However, the applications are limited due to insufficient knowledge of processing and mechanical properties, limited use of light-weight potential as well restricted surface qualities. All these drawbacks are associated with the cellular structure. The structure characteristics like skin layer thickness, cell size, density and uniformity are developed during procedure. Thus, controlling the cell formation process is the key to work against the restrictions and optimize mechanical properties.
In conventional or low-pressure foam injection molding procedure, mold filling and foaming occur simultaneously. The cellular characteristics can only be controlled in a very limited range and are often non-uniform by flow length and cross-section, not allowing a precise prediction of the mechanical performance. These limitations can be counteracted by high-pressure foam injection molding with volume-expandable molds. This special process variant may decouple filling and foaming phase and allow an active control of cellular characteristics. Cell formation mechanism may actively be shifted from cell growth to nucleation. Thus, finer-celled, homogeneous, less flowpath dependent structures with density reductions > 50 % can be achieved, and the mechanical properties can actively be influenced. This potential is often unknown due to insufficient knowledge about the process parameters and its effects on structure formation. While the conventional or low-pressure procedure has been asserted and is used in industrial applications, high-pressure procedure with volumeexpandable molds is often unknown or used in a very limited range.
This thesis deals with formation of cellular structure in thermoplastic foam injection molding process. The work focusses on influences by processing and mold technologies. High-pressure procedure in combination with volume-expandable molds – mold opening or core-back - is in focus. As a new process variant, the local core-back procedure (local mold volume expansion) is introduced, enabling a local customization of foam structures. The differences in procedures and the influence of additional process parameters are worked out. Here, especially the role of packing pressure as a key factor for structure development is discussed. To get more information on boundary conditions inside the mold during procedure and make the process more transparent, numerical simulation has been used and visualization Abstract molding trials were conducted to monitor the cell development inside the mold during processing. Furthermore, a new mold, i.a. allowing an active control of pressure drop rate was built and used. To analyze the structure and quantify the structural parameters, besides light microscopy and SEM, also x-ray tomography (μCT) was used to allow a three-dimensional characterization of structures.
In conventional or low-pressure foam injection molding procedure, mold filling and foaming occur simultaneously. The cellular characteristics can only be controlled in a very limited range and are often non-uniform by flow length and cross-section, not allowing a precise prediction of the mechanical performance. These limitations can be counteracted by high-pressure foam injection molding with volume-expandable molds. This special process variant may decouple filling and foaming phase and allow an active control of cellular characteristics. Cell formation mechanism may actively be shifted from cell growth to nucleation. Thus, finer-celled, homogeneous, less flowpath dependent structures with density reductions > 50 % can be achieved, and the mechanical properties can actively be influenced. This potential is often unknown due to insufficient knowledge about the process parameters and its effects on structure formation. While the conventional or low-pressure procedure has been asserted and is used in industrial applications, high-pressure procedure with volumeexpandable molds is often unknown or used in a very limited range.
This thesis deals with formation of cellular structure in thermoplastic foam injection molding process. The work focusses on influences by processing and mold technologies. High-pressure procedure in combination with volume-expandable molds – mold opening or core-back - is in focus. As a new process variant, the local core-back procedure (local mold volume expansion) is introduced, enabling a local customization of foam structures. The differences in procedures and the influence of additional process parameters are worked out. Here, especially the role of packing pressure as a key factor for structure development is discussed. To get more information on boundary conditions inside the mold during procedure and make the process more transparent, numerical simulation has been used and visualization Abstract molding trials were conducted to monitor the cell development inside the mold during processing. Furthermore, a new mold, i.a. allowing an active control of pressure drop rate was built and used. To analyze the structure and quantify the structural parameters, besides light microscopy and SEM, also x-ray tomography (μCT) was used to allow a three-dimensional characterization of structures.
Additional Information
Zugleich: Dissertation, Universität Kassel, 2020Druckausgabe
Link zu kassel university pressCitation
@book{doi:10.17170/kobra-202008261646,
author={Tromm, Mike},
title={Controlling cellular structure in thermoplastic foam injection molding – influence of processing and mold technologies},
publisher={kassel university press},
year={2020}
}
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2021-02-08T08:58:50Z 2021-02-08T08:58:50Z 2020 doi:10.17170/kobra-202008261646 http://hdl.handle.net/123456789/12466 Zugleich: Dissertation, Universität Kassel, 2020 eng kassel university press Namensnennung - Weitergabe unter gleichen Bedingungen 4.0 International http://creativecommons.org/licenses/by-sa/4.0/ foam injection molding core-back mold-opening cellular plastics structure development process-structure relationship lightweight construction 600 660 Controlling cellular structure in thermoplastic foam injection molding – influence of processing and mold technologies Buch Foam injection molding is a processing technology to produce foamed plastic parts in serials production, attaining an increasing interest and use in industry. However, the applications are limited due to insufficient knowledge of processing and mechanical properties, limited use of light-weight potential as well restricted surface qualities. All these drawbacks are associated with the cellular structure. The structure characteristics like skin layer thickness, cell size, density and uniformity are developed during procedure. Thus, controlling the cell formation process is the key to work against the restrictions and optimize mechanical properties. In conventional or low-pressure foam injection molding procedure, mold filling and foaming occur simultaneously. The cellular characteristics can only be controlled in a very limited range and are often non-uniform by flow length and cross-section, not allowing a precise prediction of the mechanical performance. These limitations can be counteracted by high-pressure foam injection molding with volume-expandable molds. This special process variant may decouple filling and foaming phase and allow an active control of cellular characteristics. Cell formation mechanism may actively be shifted from cell growth to nucleation. Thus, finer-celled, homogeneous, less flowpath dependent structures with density reductions > 50 % can be achieved, and the mechanical properties can actively be influenced. This potential is often unknown due to insufficient knowledge about the process parameters and its effects on structure formation. While the conventional or low-pressure procedure has been asserted and is used in industrial applications, high-pressure procedure with volumeexpandable molds is often unknown or used in a very limited range. This thesis deals with formation of cellular structure in thermoplastic foam injection molding process. The work focusses on influences by processing and mold technologies. High-pressure procedure in combination with volume-expandable molds – mold opening or core-back - is in focus. As a new process variant, the local core-back procedure (local mold volume expansion) is introduced, enabling a local customization of foam structures. The differences in procedures and the influence of additional process parameters are worked out. Here, especially the role of packing pressure as a key factor for structure development is discussed. To get more information on boundary conditions inside the mold during procedure and make the process more transparent, numerical simulation has been used and visualization Abstract molding trials were conducted to monitor the cell development inside the mold during processing. Furthermore, a new mold, i.a. allowing an active control of pressure drop rate was built and used. To analyze the structure and quantify the structural parameters, besides light microscopy and SEM, also x-ray tomography (μCT) was used to allow a three-dimensional characterization of structures. open access Tromm, Mike 2020-06-25 IX, 233 Seiten Schriftenreihe des Instituts für Werkstofftechnik / Kunststofftechnik ;; Band 11 Kassel, Universität Kassel, Fachbereich Maschinenbau Heim, Hans-Peter (Prof. Dr.) Steinbichler, Georg (Prof. Dr.) Kassel 978-3-7376-0887-9 Spritzgießen Schaumkunststoff Mechanische Eigenschaft Prozessentwicklung <Technik> Werkzeug Leichtbau Chemische Struktur publishedVersion Schriftenreihe des Instituts für Werkstofftechnik / Kunststofftechnik Band 11 true 39,00 Schriftenreihe des Instituts für Werkstofftechnik / Kunststofftechnik Naturwissenschaft, Technik, Informatik, Medizin Dissertation FB 15 / Maschinenbau Softcover DIN A5
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