Analysis of the Characteristic Flow Areas for Erdmenger-Elements to Predict the Throughput-Pressure Behavior of Co-Rotating Twin Screw Extruders by Using 3D FEM Simulation

The analysis of the throughput-pressure behavior for Erdmenger-elements has been subject of a variety of publications and is still topic of controversial debates. However, the significance of an accurate prediction of the throughput-pressure behavior for developing and optimizing compounding processes for co-rotating twin screw extruders is undisputed. For this reason, there are different mathematical descriptions to predict the melt flow behavior within the conveying elements based on the Erdmenger geometry. Most of these models base on a two-dimensional simplification for the geometry and the kinematical inversion principle. Due to increasing demands regarding compound quality and the need of new complex screw geometries to reach higher compound quality, analytical approaches to predict the flow behavior are insufficient. The use of numerical simulations is mandatory. Within this paper a new method to analyze the throughput pressure behavior based on 3D FEM simulations is discussed. In this method the characteristic flow areas channel, gap and intenneshing area of the co-rotating twin screw extruder are considered. Further the original kinematical behavior of the screws are respected. This new approach can be used to predict the melt flow more accurate and reveals potential for optimizing screw designs. Moreover, it is applicable for a vanety of screw geometries. In this investigation the method will be displayed for different conveying Erdmenger-elements. The process and geometry parameters are varied to demonstrate the method to predict the throughput-pressure behavior based on the characteristic flow areas for co-rotating twin screw extruders.