Simulation-based design of high performance internal grinding processes

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Due to the long effective contact time of the grinding grains, complex contact conditions and the difficult-to-handle coolant support, the process layout of internal traverse grinding is still challenging. Because of the high chip space and its aggressive topography, electroplated cBN grinding wheels are used to achieve high productivity when machining hardened steels. High-speed-conditions with grinding wheel velocities higher than 80 m/s significantly raise the realised material removal rate. In the fundamental project in the context of the Priority Programme 1480, a holistic simulation framework with three components was established by modelling the thermo-mechanical loads and their effects of the machining errors in different scales. At the mesoscale, a finite element model was used to model the single grain engagement achieving the thermo-mechanical loads. Due to a geometric-physical simulation the grain engagements were estimated according to the topography of the modelled grinding wheel and transformed to the process scale. On this scale, a thermomechanical coupled finite element model – considering the clamping effect, the thermal induced machining error as well as the material removal – was developed. Based on this, compensation strategies were achieved reducing the machining error along the bore by 50 percent. Without regarding the spindle complaints of grinding and workpiece spindle, a relatively high dimension error remains at the discharge area of the workpiece. The objective of the presented knowledge transfer project is the enhancement of the established holistic simulation framework due to all necessary modelling aspects to generate a prototypical solution for the industrial environment. In the focus are the implementation of the spindle complaints and the grain related wear in the different components of the simulation framework of internal traverse grinding. Due to the close cooperation with industrial application partners, Schaeffler Technologies and August Rüggeberg, the relevant industrials requirements to a simulation based layout of grinding tools and processes are defined. The usage of the holistic simulation framework secures the optimal design of the grinding wheels as well as the generation of the compensation NC-path to reduce the dimensional and form machining errors. Therefore, the application suitability test can be proven to conduct simulation based wear investigations and process ramp-ups provoked by changing the process boundary conditions prior to the process application.