Fundamental investigations to ensure the correct measurement of highly dynamic process forces in milling processes by taking material removal into account

• Applicant: Professor Dr.-Ing. Dirk Biermann
• Subject Area: Metal-Cutting and Abrasive Manufacturing Engineering
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 563788161

Force measurement technology has been a key tool to gain new insights into machining processes and for calibrating simulation models for decades. It is also increasingly used in industrial applications, e.g. for process monitoring and to create digital shadows. The frequency-dependent transfer behavior of integrated systems for process force measurement significantly limits the measurement of highly dynamic forces, like for example due to the interrupted cut during milling. By using filters, the frequency range in which the transfer function remains within a tolerance range around the ideal value of one can be significantly extended. This frequency range in which the application-specific tolerance is maintained is referred to as the usable bandwidth. In research as well as process and tool development, despite existing methods for extending the usable bandwidth, it may be necessary to minimize the sample mass in order to be able to determine process forces with minimal error. In this case, the process-related change in mass can have a particularly significant effect on the transfer function of the measuring chain, as the change in mass accounts for a high proportion of the relevant total mass. Furthermore, there are applications, for example in the form of tool wear investigations in research and development, and especially in industrial production, such as the milling of blisks, where process monitoring using force measurement technology is desired. Unfortunately the significant change in the workpiece mass occurring in these applications due to high material removal volumes, has an detrimental effect on the effectiveness of filter methods for extending the usable bandwidth. The main objective of the project is motivated by the need for filter methods suitable for use cases with a significant change in workpiece masses as a result of the cutting process. It should be made possible to use established filter methods to determine process forces with low error even for those system states that have changed in relation to the workpiece mass, for which the available transfer functions are not valid because those were determined for a previous state. As a necessary basis for this, basic knowledge about the change in the transfer function of the measuring chain as a function of the workpiece mass should first be obtained empirically and structured. Based on this new fundamental knowledge, the main goal is to develop a pair of suitable modeling and interpolation methods with which the transfer function can be predicted for all required states based on known transfer functions. By adapting a milling process simulation, the time-efficient prediction of the workpiece mass at each process time should also be made possible, on which the interpolation methods are based.

• DFG Programme: Research Grants