Coupling of analytical and numerical models to simulate the thermomechanical interactions during the milling of complex workpieces

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During the milling process of complex thin-walled workpiece structures, deformations occur. These deflections are caused by mechanical and thermal process influences and may substantially affect the machining results. Therefore, the main objective of the priority program is the modeling, the simulation and ultimately the compensation of the thermally caused deformations in the course of three project phases.During the first two phases of the project the modeling and the simulation of the deformation was treated. Within the third proposed phase, appropriate methods should be used to reduce thermally induced deformations. Measurements demonstrate a high potential for the reduction of workpiece deformations through a variation of process parameters. Therefore, a two-staged approach should be pursued, which differentiate between process sided methods on the one hand and compensation strategies on the other hand. The process sided approach pursues a change of the machining strategy by a modification of the process parameters (cutting speed v_c, feed per tooth f_z) or by changing the ratio between cutting depths (a_p) and widths (a_e). However, the compensation strategies either impair the path planning by providing the deformation of the workpiece by means of tilting the tool or counteract the deformations mechanically or thermally with additional actuators. Contrary to the compensation strategy the first two mentioned reduction methods are associated with a high technical effort and are only used, if process sided strategies are insufficient to maintain required tolerances. A process model, which was developed and validated within the first two phases of the project, builds the basis of both reduction methods. This model is able to simulate the deformations caused by the milling process of any machinable geometry so that reduction methods to avoid deformations before they are occurring can be derivated.