A calibration method on empirical basis is suggested allowing a numerical description of color and material change processes in extrusion dies. Therefore a velocity at the channel wall is introduced, where the highest residence time in the system is located. This velocity is determined from a correlation between the viscosity ration of the materials under process conditions and the time needed to complete the change. A user defined function is used to implement this velocity into the numerical simulation. However, by interacting with the calculation in runtime the function enables the analysis of changing processes in complex die geometries.
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