Publications by authors named "Georg Steinbichler"

8 Publications

  • Page 1 of 1

In Situ Detection of Interfacial Flow Instabilities in Polymer Co-Extrusion Using Optical Coherence Tomography and Ultrasonic Techniques.

Polymers (Basel) 2021 Aug 27;13(17). Epub 2021 Aug 27.

Institute of Polymer Extrusion and Compounding, Johannes Kepler University Linz, Altenberger Strasse 69, 4040 Linz, Austria.

Co-extrusion is a widely used processing technique for combining various polymers with different properties into a tailored multilayer product. Individual melt streams are combined in a die to form the desired shape. Under certain conditions, interfacial flow instabilities are observed; however, fundamental knowledge about their onset and about critical conditions in science and industry is scarce. Since reliable identification of interfacial co-extrusion flow instabilities is essential for successful operation, this work presents in situ measurement approaches using a novel co-extrusion demonstrator die, which is fed by two separate melt streams that form a well-controlled two-layer co-extrusion polymer melt flow. An interchangeable cover allows installation of an optical coherence tomography (OCT) sensor and of an ultrasonic (US) measurement system, where the former requires an optical window and the latter good direct coupling with the cover for assessment of the flow situation. The feasibility of both approaches was proven for a material combination that is typically found in multilayer packaging applications. Based on the measurement signals, various parameters are proposed for distinguishing reliably between stable and unstable flow conditions in both measurement systems. The approaches presented are well suited to monitoring for and systematically investigating co-extrusion flow instabilities and, thus, contribute to improving the fundamental knowledge about instability onset and critical conditions.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3390/polym13172880DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8434255PMC
August 2021

A Simulation-Data-Based Machine Learning Model for Predicting Basic Parameter Settings of the Plasticizing Process in Injection Molding.

Polymers (Basel) 2021 Aug 10;13(16). Epub 2021 Aug 10.

Institute of Polymer Injection Moulding and Process Automation, Johannes Kepler University Linz, Altenberger Straße 69, 4040 Linz, Austria.

The optimal machine settings in polymer processing are usually the result of time-consuming and expensive trials. We present a workflow that allows the basic machine settings for the plasticizing process in injection molding to be determined with the help of a simulation-driven machine learning model. Given the material, screw geometry, shot weight, and desired plasticizing time, the model is able to predict the back pressure and screw rotational speed required to achieve good melt quality. We show how data sets can be pre-processed in order to obtain a generalized model that performs well. Various supervised machine learning algorithms were compared, and the best approach was evaluated in experiments on a real machine using the predicted basic machine settings and three different materials. The neural network model that we trained generalized well with an overall absolute mean error of 0.27% and a standard deviation of 0.37% on unseen data (the test set). The experiments showed that the mean absolute errors between the real and desired plasticizing times were sufficiently small, and all predicted operating points achieved good melt quality. Our approach can provide the operators of injection molding machines with predictions of suitable initial operating points and, thus, reduce costs in the planning phase. Further, this approach gives insights into the factors that influence melt quality and can, therefore, increase our understanding of complex plasticizing processes.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3390/polym13162652DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8401074PMC
August 2021

Leakage-Flow Models for Screw Extruders.

Polymers (Basel) 2021 Jun 9;13(12). Epub 2021 Jun 9.

Kunststofftechnik Paderborn, Paderborn University, 33098 Paderborn, Germany.

Many theoretical analyses of extrusion ignore the effect of the flight clearance when predicting the pumping capability of a screw. This might be reasonable for conventional extruder screws with "normal" clearances but leads to errors when more advanced screw designs are considered. We present new leakage-flow models that allow the effect of the flight clearance to be included in the analysis of melt-conveying zones. Rather than directly correcting the drag and pressure flows, we derived regression models to predict locally the shear-thinning flow through the flight clearance. Using a hybrid modeling approach that includes analytical, numerical, and data-based modeling techniques enabled us to construct fast and accurate regressions for calculating flow rate and dissipation rate in the leakage gap. Using the novel regression models in combination with network theory, the new approximations consider the effect of the flight clearance in the predictions of pumping capability, power consumption and temperature development without modifying the equations for the down-channel flow. Unlike other approaches, our method is not limited to any specific screw designs or processing conditions.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3390/polym13121919DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8228144PMC
June 2021

Properties of Starve-Fed Extrusion on a Material Containing a VHMWPE Fraction.

Polymers (Basel) 2021 Mar 19;13(6). Epub 2021 Mar 19.

Institute of Polymer Extrusion and Compounding, Johannes Kepler University Linz, Altenberger Str. 69, 4040 Linz, Austria.

Single-screw extruders are usually operated with the screw fully filled (flood-fed mode) and not partially filled (starve-fed mode). These modes result in completely different processing characteristics, and although starve-fed mode has been shown to have significant advantages, such as improved mixing and melting performance, it is rarely used, and experimental studies are scarce. Here, we present extensive experimental research into starve-fed extrusion at feeding rates as low as 25%. We compared various operating parameters (e.g., residence time, pressure build-up, and melting performance) at various feeding rates and screw speeds. The results show a first insight into the performance of starve-fed extruders compared to flood-fed extruders. We explored starve-fed extrusion of a polyethylene material which contains a Very High Molecular Weight Polyethylene fraction (VHMWPE). VHMWPE offers several advantages in terms of mechanical properties, but its high viscosity renders common continuous melt processes, such as compression molding, ram extrusion and sintering, ineffective. This work shows that operating single-screw extruders in extreme starve-fed mode significantly increases residence time, melt temperature, and improves melting and that-in combination-this results in significant elongation of VHMWPE particles.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3390/polym13060944DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8003239PMC
March 2021

Backpressure Optimization in Foam Injection Molding: Method and Assessment of Sustainability.

Polymers (Basel) 2020 Nov 16;12(11). Epub 2020 Nov 16.

Institute of Polymer Injection Molding and Process Automation, Johannes Kepler University Linz, Altenberger Strasse 69, A-4040 Linz, Austria.

Inspired by the Industry 4.0 trend towards greater user-friendliness and self-optimization of machines, we present a novel approach to reducing backpressure in foam injection molding. Our method builds on the compressibility of polymer-gas mixtures to detect undissolved gas phases during processing at insufficient backpressures. Identification of a characteristic behavior of the bulk modulus upon transition from homogeneous to heterogeneous polymer-gas mixtures facilitated the determination of the minimum pressure required during production to be determined, as verified by ultrasound measurements. Optimization of the pressure conditions inside the barrel by means of our approach saves resources, making the process more sustainable. Our method yielded a 45% increase in plasticizing capacity, reduced the torque needed by 24%, and required 46% less plasticizing work and lower pressures in the gas supply chain. The components produced exhibited both improved mechanical bending properties and lower densities. From an economic point of view, the main advantages of optimized backpressures are reduced wear and lower energy consumption. The methodology presented in this study has considerable potential in terms of sustainable production and offers the prospect of fully autonomous process optimization.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3390/polym12112696DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7698219PMC
November 2020

Application of Network Analysis to Flow Systems with Alternating Wave Channels: Part B. (Superimposed Drag-Pressure Flows in Extrusion).

Polymers (Basel) 2020 Aug 24;12(9). Epub 2020 Aug 24.

Institute of Polymer Extrusion and Compounding, Johannes Kepler University Linz, 4040 Linz, Austria.

Due to progress in the development of screw designs over recent decades, numerous high-performance screws have become commercially available in single-screw extrusion. While some of these advanced designs have been studied intensively, others have received comparatively less attention. We developed and validated a semi-numerical network-theory-based modeling approach to predicting flows of shear-thinning polymer melts in wave-dispersion screws. In the first part (Part A), we systematically reduced the complexity of the flow analysis by omitting the influence of the screw rotation on the conveying behavior of the wave zone. In this part (Part B), we extended the original theory by considering the drag flow imposed by the screw. Two- and three-dimensional melt-conveying models were combined to predict locally the conveying characteristics of the wave channels in a discretized flow network. Extensive experiments were performed on a laboratory single-screw extruder, using various barrel designs and wave-dispersion screws. The predictions of our semi-numerical modeling approach for the axial pressure profile along the wave-dispersion zone accurately reproduce the experimental data. Removing the need for time-consuming numerical simulations, this modeling approach enables fast analyses of the conveying behavior of wave-dispersion zones, thereby offering a useful tool for design and optimization studies and process troubleshooting.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3390/polym12091900DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7564092PMC
August 2020

Development of an Analytical Model to Describe the Disperse Melting in Wave-Dispersion Screws.

Polymers (Basel) 2020 Apr 18;12(4). Epub 2020 Apr 18.

Institute of Polymer Extrusion and Compounding, Johannes Kepler University Linz, Linz 4040, Austria.

The progressive development of new screw concepts in single screw extrusion also makes it necessary to develop new models for the correct process description. When looking at wave-dispersion screws, the disperse melting behavior should be mentioned in particular, which has so far been less researched and modeled than the conventional melting behavior, as it occurs in standard screws. Therefore, an analytical model is presented in this paper, which considers the disperse melting under consideration of the melt and solid temperature. The basic assumption is Fourier heat conduction from the melt surrounding the particles into the particles. Furthermore, the melt temperature development by dissipation and the cooling effects were modeled analytically. Additionally, the solid bed temperature was modeled by a 2D-FDM method. By dividing the screw into several calculation sections with constant boundary conditions, it was subsequently possible to calculate the melting process over the screw length. The model developed shows comprehensible results in verification and successfully reproduces the solids content over the screw length with a mean deviation of absolute 11% in validation tests using cooling/pulling-out experiments.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3390/polym12040946DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7240452PMC
April 2020

Application of Network Analysis to Flow Systems with Alternating Wave Channels: Part A (Pressure Flows).

Polymers (Basel) 2019 Sep 12;11(9). Epub 2019 Sep 12.

Institute of Polymer Extrusion and Compounding, Johannes Kepler University Linz, 4040 Linz, Austria.

Wave-dispersion screws have been used industrially in many types of extrusion processes, injection molding, and blow molding. These high-performance screws are constructed by replacing the metering section of a conventional screw with a melt-conveying zone consisting of two or more parallel flow channels that oscillate periodically in-depth over multiple cycles. With the barrier flight between the screw channels being selectively undercut, the molten resin is strategically forced to flow across the secondary flight, assuring repeated cross-channel mixing of the polymer melt. Despite the industrial relevance, very few scientific studies have investigated the flow in wave-dispersion sections in detail. As a result, current screw designs are often based on traditional trial-and-error procedures rather than on the principles of extrusion theory. This study, which was split into two parts, was carried out to systematically address this issue. The research reported here (Part A) was designed to reduce the complexity of the problem, exclusively analyzing the pressure-induced flows of polymer melts in wave sections. Ignoring the influence of the screw rotation on the conveying characteristics of the wave section, the results could be clearly assigned to the governing type of flow mechanism, thereby providing a better understanding of the underlying physics. Experimental studies were performed on a novel extrusion die equipped with a dual wave-channel system with alternating channel depth profiles. A seminumerical modeling approach based on network theory is proposed that locally describes the downchannel and cross-channel flows along the wave channels and accurately predicts the pressure distributions in the flow domain. The solutions of our seminumerical approach were, moreover, compared to the results of three-dimensional non-Newtonian CFD simulations. The results of this study will be extended to real screw designs in Part B, which will include the influence of the screw rotation in the flow analysis.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3390/polym11091488DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6780909PMC
September 2019
-->