When it comes to the design of extrusion line components such as single‐screw extruders or extrusion dies, no one has yet succeeded in developing a well‐functioning concept for wall‐slipping materials. This article examines the fundamental influences of the wall slippage effect on flow behavior in the extrusion die and plastification unit. New and extended methods of calculation for describing this flow phenomenon are presented for both these extrusion line components, and the general possibilities for linking the two approaches are discussed. Diagram of the flow curve (τ = shear stress, $\dot \gamma$ = shear rate) of wall‐slipping plastics for constant pressure.magnified imageDiagram of the flow curve (τ = shear stress, $\dot \gamma$ = shear rate) of wall‐slipping plastics for constant pressure.