Extrusion International 2-2023

46 Extrusion International 2/2023 ing behaviour accurately with a high spatial resolution in the tube formation zone. In a new series of tests, the for- mation zone is therefore recorded by camera technology and the stretching of the film and the temperature gradi- ent are described using polynomials. A correlation analysis of the polynomial coefficients obtained shows that they correlate strongly with each other. An extension of the property model by means of classical linear regression is therefore impossible. However, the method of Partial Last Square regression (PLS) shows that the coefficients deter- mined in combination with the already established vari - ables should be considered for further model building. In further investigations, modern modelling methods, such as artificial neural networks, are to be examined. One possibility is the development of a hybrid model (black box model as booster), which uses the property model according to Ohlendorf as input in addition to the newly described poly - nomial coefficient. A purely data-driv- en modelling (black box model) should also be considered. Furthermore, the improved process model should be investigated to evaluate whether the transferability to other machines might be enabled by the extended descrip - tion of the tube formation zone. Acknowledgments The construction of the Plastics Innovation Center 4.0 (PIC 4.0) is supported by funds from the state of North Rhine-Westphalia and the European Regional Develop- ment Fund (EFRE). We would like to express our grati- tude to all institutions. Furthermore, the authors would like to thank Sabic Europe B. V., Geelen, Netherlands, for the materials provided for experimental purposes. Institute for Plastics Processing (IKV) at RWTH Aachen University Daniel Grüber, M.Sc. RWTH, Thermoforming daniel.grueber@ikv.rwth-aachen.de Seffenter Weg 201, 52074 Aachen, Germany BLOWN FILM EXTRUSION – FROM THE RESEARCH References [Dis13] Dispan, J.: Kunststoffverarbeitung in Deutschland. Company script, 2013 [Hau99] Hauk, J.: Entwicklung eines Simulationsprogrammes für den Schlauchfolienextrusionsprozess. RWTH Aachen Uni- versity, Dissertation, 1999 [Lim13] Limper, A.: Verfahrenstechnik zur Thermoplastextru- sion. München: Carl Hanser Verlag, 2013 [MHMS14] Menges, G.; Haberstroh, E.; Michaeli, W.; Schmachtenberg, E.:Menges Werkstoffkunde Kunststoffe. München: Carl Hanser Verlag, 2014 [NN19c] N.N.: Plastics – the facts 2019. Report, Düsseldorf, 2019 [Ohl04] Ohlendorf, F.: Vorhersage der mechanischen Folieneigenschaften bei der Schlauchfolienextrusion. RWTH Aachen University, Dissertation, 2004 Symbols Symbol Description a Percentage deviation i l Take-up ratio i q Blow-up ratio i t Temperature ratio i v Volume flow ratio i f Frost line ratio i d Thickness ratio L, q, t, v, f, d, k Regrission coefficients r 2 Coefficient of determination Abbreviations Notation Description BR(h) Bubble radius BUR Blow-up ratio PE-HD High density polythlylene PE-LD Low density polythlylene PLS Partial Last Square Regression TUR Take-up ratio Picture 6: Acquisition of the cooling process and approximation by a 4th degree polynomial