Abstract:A review paper is presented on optimization and scale-up for polymer extrusion, both single screw and twin screw extrusion. Optimization consists in obtaining a multidimensional space of process output variables (response surface) on the basis of an appropriate set of input data and searching for extreme values in this space. Scaling consists in changing the scale of the process according to specific criteria, that is, changing the process while maintaining the scaling parameters at a level that is as close to… Show more
“…In the process of scaling down SSE, a reduction in the viscous dissipation was thus witnessed in our previous work. This could be made clearer upon comparing the melting profiles for micro-extrusion and conventional extrusion under typical operation conditions for each technique on its own [38], consistent with preliminary results [47]. We also put forward in our previous theoretical study that screw parameters such as the screw frequency and pitch angle and material parameters such as the power-law index influence the relative position of the final EAM melting point.…”
To improve the product quality of polymeric parts realized through extrusion-based additive manufacturing (EAM) utilizing pellets, a good control of the melting is required. In the present work, we demonstrate the strength of a previously developed melt removal using a drag framework to support such improvement. This model, downscaled from conventional extrusion, is successfully validated for pellet-based EAM—hence, micro-extrusion—employing three material types with different measured rheological behavior, i.e., acrylonitrile-butadiene-styrene (ABS), polylactic acid (PLA) and styrene-ethylene-butylene-styrene polymer (SEBS). The model’s validation is made possible by conducting for the first time dedicated EAM screw-freezing experiments combined with appropriate image/data analysis and inputting rheological data. It is showcased that the (overall) processing temperature is crucial to enable similar melting efficiencies. The melting mechanism can vary with the material type. For ABS, an initially large contribution of viscous heat dissipation is observed, while for PLA and SEBS thermal conduction is always more relevant. It is highlighted based on scanning electron microscopy (SEM) analysis that upon properly tuning the finalization of the melting point within the envisaged melting zone, better final material properties are achieved. The model can be further used to find an optimal balance between processing time (e.g., by variation of the screw frequency) and material product performance (e.g., strength of the printed polymeric part).
“…In the process of scaling down SSE, a reduction in the viscous dissipation was thus witnessed in our previous work. This could be made clearer upon comparing the melting profiles for micro-extrusion and conventional extrusion under typical operation conditions for each technique on its own [38], consistent with preliminary results [47]. We also put forward in our previous theoretical study that screw parameters such as the screw frequency and pitch angle and material parameters such as the power-law index influence the relative position of the final EAM melting point.…”
To improve the product quality of polymeric parts realized through extrusion-based additive manufacturing (EAM) utilizing pellets, a good control of the melting is required. In the present work, we demonstrate the strength of a previously developed melt removal using a drag framework to support such improvement. This model, downscaled from conventional extrusion, is successfully validated for pellet-based EAM—hence, micro-extrusion—employing three material types with different measured rheological behavior, i.e., acrylonitrile-butadiene-styrene (ABS), polylactic acid (PLA) and styrene-ethylene-butylene-styrene polymer (SEBS). The model’s validation is made possible by conducting for the first time dedicated EAM screw-freezing experiments combined with appropriate image/data analysis and inputting rheological data. It is showcased that the (overall) processing temperature is crucial to enable similar melting efficiencies. The melting mechanism can vary with the material type. For ABS, an initially large contribution of viscous heat dissipation is observed, while for PLA and SEBS thermal conduction is always more relevant. It is highlighted based on scanning electron microscopy (SEM) analysis that upon properly tuning the finalization of the melting point within the envisaged melting zone, better final material properties are achieved. The model can be further used to find an optimal balance between processing time (e.g., by variation of the screw frequency) and material product performance (e.g., strength of the printed polymeric part).
“…Covas i Cunha [36][37][38] oraz Berzin i inni [39] przedstawili także koncepcje zwiększania skali procesu wytłaczania dwuślimakowego współbieżnego. Zagadnienia te zostały ostatnio podsumowane w pracy przeglądowej [40]. Proponowane zwiększenie skali procesu wytłaczania na podstawie technik ewolucyjnych polega na pozyskiwaniu danych na podstawie badań symulacyjnych procesu i następnie zastosowaniu odpowiedniej procedury ewolucyjnej (algorytmów genetycznych).…”
Na podstawie badań symulacyjnych opracowano metodę zwiększania skali procesu jednoślimakowego wytłaczania tworzyw polimerowych, z zastosowaniem technik ewolucyjnych (algorytmów genetycznych). Do symulacji procesu wytłaczania stosowano program GSEM (Global Screw Extrusion Model), a do zwiększenia skali specjalnie w tym celu opracowany program GASES (Genetic Algorithms Screw Extrusion Scaling). Jako kryteria stosowano jednostkowe zużycie energii, szybkość uplastyczniania i szybkość wzrostu temperatury tworzywa. Uzyskano znaczący wzrost wydajności procesu wytłaczania.
“…Koncepcję zwiększania skali procesu wytłaczania jednoślimakowego w warunkach dozowania grawitacyjnego autor przedstawił we wcześniejszych publikacjach [43,44]. Przedmiotem niniejszego artykułu jest zwiększanie skali procesu wytłaczania jednoślimakowego z użyciem dozownika przy zastosowaniu algorytmów genetycznych i specjalnie opracowanego programu GASES ST.…”
Section: Program Do Zwiększania Skali Procesu Wytłaczaniaunclassified
Opracowano metodę zwiększania skali procesu wytłaczania jednoślimakowego z dozowaniem tworzywa przy użyciu dozownika. Badania przeprowadzono na podstawie modelu komputerowego procesu przy zastosowaniu algorytmów genetycznych (technik ewolucyjnych). Podstawę metody stanowi program symulacji procesu wytłaczania GSEM (Global Screw Extrusion Model), który jest źródłem danych do optymalizacji, oraz specjalnie opracowany program zwiększania skali procesu GASES ST (Genetic Algorithm Screw Extrusion Scaling for Starve). Prace dotyczyły zmiany skali z poziomu wytłaczarki o średnicy ślimaka D = 45 mm do poziomu wytłaczarki o D = 60, przy zachowaniu takiego samego stosunku L/D. Na podstawie symulacji zoptymalizowano szybkość obrotową ślimaka wytłaczarki, temperaturę poszczególnych stref układu uplastyczniającego i szybkość dozowania. Proces przeprowadzono wg kryterium minimalnego jednostkowego zużycia energii, maksymalnej szybkości uplastyczniania i najniższej temperatury tworzywa na wyjściu z głowicy.
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