Development of a methodology for the extension and deflection-based calibration of an axis-position sensitive process force model

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Process simulations enable an improved design of milling processes in order to achieve the required workpiece quality and high productivity. For example, geometric physically-based process simulations are used to predict the resulting surface quality and avoid chatter vibrations. These simulations use models of the compliance of the production system and the process forces. The empirical calibration of the cutting force models is performed using various optimization techniques, such as evolutionary algorithms, on the basis of force measurements for the analyzed combination of material and tool. The parameterization of a force model is ambiguous, as different parameter value combinations can lead to a comparably good modeling of the process forces. However, these different calibrations can result in the prediction of different deflections when simulating vibrations. Furthermore, the dynamometers used for force measurement limit the range of process parameter values which can be used in the investigations due to their transfer behavior and compliance.In this project, a new methodology for the parameterization of process force models will be developed. By taking into account tool deflections measured in the process, the unambiguous determination of process force coefficients will be enabled. Based on the physical interactions between the tool deflections and the exciting process forces, it is possible to draw conclusions from the deflections to the process forces, considering the known compliance of the system. After an initial parameterization based on force measurements for a material-tool combination, the parameter optimization should then be carried out based on deflection measurements. In contrast to force measurements, these are performed contact-free using, e.g., eddy current sensors and have no influence on the process behavior.To ensure sufficient prediction accuracy for the simulation of milling processes with tools with spherical form elements, an extended force model is to be developed. Based on the cutting force model according to Kienzle, both, the tool orientation and the varying engagement conditions along the cutting edge will be taken into account. Furthermore, investigations on the transferability of the model calibration to other materials (using steel and aluminum materials as examples) and tools are planned. The new methodology for calibrating the extended force model based on measured deflections is expected to achieve an unambiguous prediction of process forces and tool deflections and an extended range of validity of the models.