Mechanics of the Solid Bed in Single Screw Extruders
Final Report Abstract
In addition to conveying and homogenizing, melting is one of the main tasks of a plasticizing extruder. Achieving high melt quality requires the accurate prediction of the melting process, which is a key aspect in the design of single-screw extruders. Over the past decades, various models have been developed for the calculation of the melting process, enabling predictions of the melting length. One of the most frequently cited models is the melting model by TADMOR, which is based on the experimental observations of MADDOCK. This model has been repeatedly addressed in the literature and modified by various authors. An analytically solvable modification of TADMOR's melting model was developed by POTENTE, allowing for predictions of the entire melting process with short calculation times. As part of this research project, POTENTE's model was revisited and analyzed concerning key model assumptions. The primary objective of the research project was to improve the calculation accuracy of the melting behavior, with special consideration given to the mechanics of the solid bed. Central aspects of the investigation included the velocity of the solid bed in compression zones and the validity range of MADDOCK's melting behavior. Furthermore, the experimental investigations revealed additional aspects that also contributed to the improvement of the model. A significant aspect was the delayed formation of melt pool due to the reduced heat input into the porous bulk material at the beginning of the screw channel. In particular, by incorporating the reduced heat input and improving the assumption of the phase boundary temperature into the theoretical model, a significant improvement in model quality was achieved. These findings were also utilized to improve a Computational Fluid Dynamics (CFD) simulation model, resulting in an increase in its computational accuracy. In addition to improving the model quality, dynamic pressure measurements were evaluated within this research project as a method for investigating the melting process. A test rig was also developed and commissioned, enabling the study of bulk material strengths under extrusion conditions. Using this test rig, the strength of the solid bed could be described under various conditions.
Publications
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Improvement in an Analytical Approach for Modeling the Melting Process in Single-Screw Extruders. Polymers, 16(22), 3130.
Knaup, Felix; Brüning, Florian & Schöppner, Volker
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Improvement of a Numerical Two-Phase Simulation Model for the Melting Process in Single-Screw Extruders Based on Experimental Investigations. In: Proceedings of the 40th International Conference of the Polymer Processing Society (PPS-40), Auckland, 2025. (Status: Angenommen)
Knaup, F. & Schöppner, V.
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Improving an Analytical Model of Melting in Single Screw Extruders considering the Delay Zone Length. In: Conference Proceedings ANTEC 2025, Philadelphia, 2025. (Status: Angenommen)
Knaup, F.; Brüning, F. & Schöppner, V.
