Abstract
This Ph.D. project researches the implementation of digital manufacturing technologies for polymer processing to enable an increased complexity and the requirement for manufacturing optimization. To overcome the current limitations of the conventional tooling process chain in polymer profile extrusion, the implementation of additive manufacturing (AM) and simulation optimization for direct tooling is investigated.
State of the art for polymer extrusion was first determined to establish and identify the critical components of the tooling process chain, along with a review of the industrial practices on tool design. Likewise, state of the art for AM was presented with a particular focus dedicated to metal additive manufacturing (MAM). Specifically, laser powder bed fusion (LPBF) and metal fused deposition modeling (FDM) was further reviewed. An essential part of the research revolves around the metrological framework of surface characterization and dimensional analysis of MAM parts and their characteristic features. The literature study within profile extrusion and AM represents the foundation on which the research has been defined and further developed.
An indepth analysis of MAM for tooling was presented, and a schematic framework was developed to characterize the implementation stages of digital technologies for tooling applications. Based on the combined knowledge of the two main topics, a conceptual framework with design and implementation guidelines was presented for MAM direct tooling in profile extrusion.
Experimental investigations have been applied to evaluate and compare different MAM technologies with conventionally manufactured benchmarks. The influence of the rough surface topography of MAM parts on the polymer melt flow in the extrusion die was one of the primary focuses of the experimental work. A novel methodology for surface roughness evaluation was presented based on the characteristic surface topography of metal FDM parts. The experimental work indicated that the influence of MAM tools with a surface roughness of around ten times that of the conventional tool only resulted in a final extrudate product surface roughness of about twice that of the conventional tool. Furthermore, the different characteristic surface topographies of the MAM tool provided different final extrudate quality results, dependent on the applied AM technology. For selected combinations of processing parameters and polymers, the MAM tools manufactured using metal FDM were on par with the conventionally manufactured tools.
Simulation optimization is an essential component in the digitally enabled tooling process chain, and a simulation model of the experimental die setup was proposed and experimentally validated. With accurate simulationrelated material data, the model predicted an extrusion die pressure within 10% of the experimentally acquired values. Based on the validated simulation model, a conceptual framework for flow channel shape optimization was presented, including recommendations on relevant objective functions.
Lastly, a case study on direct tooling using polymerbased AM technologies were presented. Based on the findings from previous work, a new material and AM process were proposed, and experimental tests were performed to evaluate the suitability of the process chain. The tested setup successfully produced extrudate products and withstood the high pressure and temperature combination in the manufacturing setup. This preliminary case study indicates a significant potential for small batch production or prototyping activities in profile extrusion that is otherwise characterized by high tooling costs and sizeable minimum batch quantities. The results from the presented investigations give a strong indication of the successful implementation of AM within the tooling process chain of profile extrusion. The integration of simulation optimization in the early stages of the tooling process chain would allow for a significantly reduced lead time and tooling cost while ensuring optimal die performance with a high level of die flow balance and increased extrusion rates.
The resulting optimal die flow channel geometries are enabled by the freedom of design characterizing MAM as opposed to the limitations of the conventional process chain based on subtractive manufacturing. With the careful selection of a suitable AM technology, implementation of an optimized flow path geometry, and an understanding of the opportunities and limitations of the manufacturing process, the continued development of tooling for extrusion will ensure a new level of manufacturing excellence.
State of the art for polymer extrusion was first determined to establish and identify the critical components of the tooling process chain, along with a review of the industrial practices on tool design. Likewise, state of the art for AM was presented with a particular focus dedicated to metal additive manufacturing (MAM). Specifically, laser powder bed fusion (LPBF) and metal fused deposition modeling (FDM) was further reviewed. An essential part of the research revolves around the metrological framework of surface characterization and dimensional analysis of MAM parts and their characteristic features. The literature study within profile extrusion and AM represents the foundation on which the research has been defined and further developed.
An indepth analysis of MAM for tooling was presented, and a schematic framework was developed to characterize the implementation stages of digital technologies for tooling applications. Based on the combined knowledge of the two main topics, a conceptual framework with design and implementation guidelines was presented for MAM direct tooling in profile extrusion.
Experimental investigations have been applied to evaluate and compare different MAM technologies with conventionally manufactured benchmarks. The influence of the rough surface topography of MAM parts on the polymer melt flow in the extrusion die was one of the primary focuses of the experimental work. A novel methodology for surface roughness evaluation was presented based on the characteristic surface topography of metal FDM parts. The experimental work indicated that the influence of MAM tools with a surface roughness of around ten times that of the conventional tool only resulted in a final extrudate product surface roughness of about twice that of the conventional tool. Furthermore, the different characteristic surface topographies of the MAM tool provided different final extrudate quality results, dependent on the applied AM technology. For selected combinations of processing parameters and polymers, the MAM tools manufactured using metal FDM were on par with the conventionally manufactured tools.
Simulation optimization is an essential component in the digitally enabled tooling process chain, and a simulation model of the experimental die setup was proposed and experimentally validated. With accurate simulationrelated material data, the model predicted an extrusion die pressure within 10% of the experimentally acquired values. Based on the validated simulation model, a conceptual framework for flow channel shape optimization was presented, including recommendations on relevant objective functions.
Lastly, a case study on direct tooling using polymerbased AM technologies were presented. Based on the findings from previous work, a new material and AM process were proposed, and experimental tests were performed to evaluate the suitability of the process chain. The tested setup successfully produced extrudate products and withstood the high pressure and temperature combination in the manufacturing setup. This preliminary case study indicates a significant potential for small batch production or prototyping activities in profile extrusion that is otherwise characterized by high tooling costs and sizeable minimum batch quantities. The results from the presented investigations give a strong indication of the successful implementation of AM within the tooling process chain of profile extrusion. The integration of simulation optimization in the early stages of the tooling process chain would allow for a significantly reduced lead time and tooling cost while ensuring optimal die performance with a high level of die flow balance and increased extrusion rates.
The resulting optimal die flow channel geometries are enabled by the freedom of design characterizing MAM as opposed to the limitations of the conventional process chain based on subtractive manufacturing. With the careful selection of a suitable AM technology, implementation of an optimized flow path geometry, and an understanding of the opportunities and limitations of the manufacturing process, the continued development of tooling for extrusion will ensure a new level of manufacturing excellence.
| Original language | English |
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| Place of Publication | Kgs. Lyngby |
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| Publisher | Technical University of Denmark |
| Number of pages | 229 |
| ISBN (Electronic) | 9788774757085 |
| Publication status | Published - 2022 |
Keywords
- Industry 4.0
- Polymer profile extrusion
- Metal additive manufacturing
- Laser powder bed fusion
- Metal fused material deposition
- Tooling