Model based toolpath correction for ultra-precision machining

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In the first project phase a cross table was developed, constructed, put into operation and characterized to increase the machining dynamics for UP raster milling. By identifying the modal eigenmodes and an additional real time parameter identification a compensation of structural vibration of the axes was realized. Beside the compensated structural vibrations, the surface quality is reduced by the interactions between multiple feed axes which lead to dynamic path deviations as well as the influences of the subsystems of the other projects of the research group. This can be counteracted by a comprehensive compensation of disturbances between multiple feed axes. Therefore, the goal of the second project phase is to reduce dynamic path deviations of the entire UP-HPC system while taking into account the other subsystems and the cutting process. Three focal points are pursued to reach this goal. The transfer of the existing compensation methods to three feed axes, the extension of model based filter and control methods and the increase of the robustness of the overall system. The transfer of the compensation methods requires a detailed understanding of the three-dimensional path behavior, in this case that is especially the trajectory of the tool and the path velocities. To describe the path behavior a direct test method for the UP raster milling is developed, that quantifies the main aspects of the path behavior with characteristic values. This enables a systematic analysis of the interactions, that need to be examined, and the development of an interconnection between the sub-models, which were created in the first project phase. In this way a model of the overall axis system is created. To minimize dynamic path deviations extended model based filter and control methods are examined. These include the Input-Shaping, to reduce cross-talk between the axes, as well as a tracking control, to increase the dynamic. These methods, which are known from the HPC manufacturing, need to be adapted to the high requirements for the precision of the UP manufacturing. Because of this, the underlying models of these methods are implemented in such a way, that they can be adapted to different process states, by using methods like the continuous parameter identification.In the last year of the project phase the potentials and limits of the developed methods are researched, taking into account the vibration stimulation of the cutting process and the influences of the additional components. Further, the overall performance of all developed methods is evaluated in cutting tests.