Melting in Single-screw Extruders with Grooved Plasticizing Barrel
A very promising high performance extruder which is already used in the European industry consists of a combination of a grooved plastizing cylinder with a barrier screw. The cylinder is provided with grooves both in the feed and the melting zone. Although the exceptional performance of this extruder system has already been demonstrated, the exact mechanisms during the melting process are still not fully understood. Therefore, the research of the melting process in this type of extruders is of scientific interest.
Based on the theory of melting in conventional single-screw extruders, a physical-mathematical model for the grooved plastizicing cylinder has been developed. Two important assumptions of the mathematical model are that the solid bed width corresponds to the solid channel width and that the grooves are completely filled with melt. The molten plastic is transported from the solid channel into the melt channel through the grooves. In this way, the melt film in the region between two grooves is minimized.
For the experimental investigation of the melting process in the single-screw extruder with grooved barrel (SSGB), experiments were carried out at various plasticizing units. In connection with the extrusion, trials on dynamic pressure measurements were performed at various locations along the cylinder. Subsequent analysis of the pressure signals allowed characterization of the melting process. Additionally, screw freezing experiments were per-formed for axially grooved cylinder. A solid bed was clearly identified in the solid channel, and it was also possible to identify the melt flow in the grooves. By means of these experiments, the melting process can be characterized and some of the theoretical ideas about the melting mechanism can be confirmed.
The mathematical model was compared with the results of the experimental investigations. In addition to the experimentally provided evidence of the validity of key model assumptions, the simulation results were also validated by means of experimental tests. However, the melting rate of the SSGB could not be measured directly. For this, it would be necessary to develop a measure device in the future.Lesen Sie die deutsche Zusammenfassung auf Kunststoffe.de
Single-Screw Extruder, Extruder Design, Melting, Screw Design, Simulation, Melt Flow, Grooved Barrel
Institute / chair: Fakultät für Energie-, Verfahrens- und Biotechnik der Universität Stuttgart
Technical consultant for expert services: Prof. Dr.-Ing. Christian Bonten (Betreuer), Prof. Dr.-Ing. Johannes Wortberg
Publication year: 2016
Provider: Wissenschaftlicher Arbeitskreis Kunststofftechnik (WAK) / Kunststoffe.de
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