The application of the mapping method [1, 2] on fully three dimensional flows with dynamic boundaries is presented. The computational domain is a (three dimensional) section of a particular type of screw element in a closely intermeshing corotating twin screw extruder Screw elements include transport, different kneading, and counterconveying zones, for each of which a mapping matrix has to be constructed. In the future, different screw assemblies could be studied by combining distinct mapping matrices, much like an actual screw is assembled front distinct modules. In this paper, the principle and applicability of the mapping method is demonstrated by the analysis of a fully filled transporting section of the corotating twin screw extruder Concentration and residence time distributions can be computed straight fowardly and the volume average intensity of segregation is chosen as a characteristic mixing measure to quantitatively describe distributive mixing.