Aluminum profiles manufactured by extrusion molding gain more and more importance in the production of lightweight structures. The development of adequate machining of thin-walled and complex shaped 3D-structures requires detailed knowledge about the process conditions. The planning of a machining process has to avoid collisions between tool and workpiece and to take into account the material properties resulting from internal material stresses and temperatures. Finite element analysis (FEA) is a useful simulation method to examine temperatures and stresses resulting from loads occurring during the machining process and the application of the component. In this article, a discrete milling simulation is introduced which allows a detailed view on the exact engagement condition at each moment of the cutting process. By importing simulated FEA results regarding the component load during its usage the milling simulation is able to generate collision free and feed optimized NC-paths with respect to internal workpiece conditions.