Thermomechanical Deformation of Complex Workpieces in Milling and Drilling Processes

In this chapter the work of an interdisciplinary collaboration for modeling thermomechanical deformations in dry milling and drilling processes is presented. The simulation based approach allows the prediction of structural workpiece deformation due to thermal effects occurring during the machining process. Geometric changes of the workpiece volume and the current engagement of tool and workpiece are included in the developed model. The model is applied for the optimization of NC paths with respect to workpiece deformations. The combined model is assembled by individual sub-models, which are coupled to account for interactions with each other. A dexel model is applied for contact zone analysis of tool and workpiece and also allows efficient geometric modeling of the workpiece surface. Geometric process variables of the contact zone are passed to the process model which provides thermal and mechanical loads for the thermomechanics. The thermomechanical behaviour is numerically approximated using finite elements on the time depending co-domain of the dexel model together with thermal and mechanical loads provided by the process model. In all, a closed loop between Boolean material removal, process forces, heat flux and thermo-elastic deformation is established and allows an accurate prediction of workpiece deformation and shape deviations. Furthermore, the simulation operates as a forward model for an NC path optimization. A significant improvement of form deviation is achieved with the approach.