CFD-based Simulation of Operational Point Influences on Product Changing Processes

In the means of production, saving resources is becoming more and more a priority optimizing plastics extrusion processes. The analysis of color and material changes has become very interesting to prevent unnecessary material loss. This interest is justified especially due to increasing numbers of changing processes as a reaction of more individual product specifications and thus decreasing lot sizes in the last decades. It can be shown that commercial numerical tools are capable of plausible calculations of changing processes, enabling process observations and giving the possibility of predicting different influences. Due to the highly dynamical character of the flow behavior in the control volume, a transient approach is necessary to show the effects of different operational points on product changes. To determine the progress of the product change the volume of fluid model (VOF) as multiphase approach is used. The analysis of influences from operational points on the changing process is achieved by separate observations of two important input parameters. On one hand the effects of varied mass flow rates as inlet boundary conditions and on the other hand different mass temperatures are observed. To check the plausibility of the calculation method the results are discussed referring to exemplary experimental data in qualitative comparison. The experimental data is obtained using special laboratory equipment neglecting influences from the extruder and taking only the die as control volume into consideration.