The next step towards virtual machine tools: Simulation of damping effects caused by the machine-process interaction

• Applicant: Professor Dr.-Ing. Michael Friedrich Zäh
• Subject Area: Production Automation and Assembly Technology ; Metal-Cutting and Abrasive Manufacturing Engineering
• Term: from 2019 to 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 420581965

The interaction between the machine tool and the process can lead to unwanted vibrations and even instabilities such as chatter. The consequences are increased tool wear, insufficient machining results up to damages to the machine tool. In order to avoid these unwanted vibrational phenomena and to increase the cutting performance of machine tools, it is necessary to simulate the interaction between the machine and the process with high accuracy. In the research group "Damping effects in machine tools" funded by the German Research Foundation (DFG), the damping in the mechatronic machine tool structure was analyzed and predictable linear and nonlinear damping models were identified for the different dissipation sources. By using an appropriate modeling approach, the various influencing factors on the damping of the mechatronic machine tool structure were taken into account in the simulation. This modeling approach together with the identified damping models allows to predict the dynamic behavior of a machine tool structure with high accuracy. In order to consider the cutting process in addition to the machine tool structure within the simulation, appropriate cutting force models are needed. The Research group addressed the main problem with the simulation of the machine tool structure: Modeling of the damping. However for the process damping effect there are usually no practicable models and parameters available. Process damping results from the interaction between the tool and the workpiece and affects in particular the process stability at low cutting speeds. This plays an important role in the machining of difficult-to-cut-materials like titanium and nickel alloys. Neglecting process damping leads to an inaccurate prediction of the stability limit. In addition, the damping in the machine tool structure is influenced by the process: Varying the machining positions, feed rates, spindle speeds as well as loads in the machine components has an impact on the structure’s damping coefficients, but is not taken into account in the simulation. In order to represent the overall system of the machine tool and the process in the simulation with sufficient accuracy it is necessary to consider the influences of the process on the overall damping. This represents the next step to the virtual machine tool, subsequent to the research unit. By continuing to use and expanding the physical machine tool, the gap in modeling the damping in the machine tool and the process can be closed and the simulation accuracy can be increased significantly. This results in new possibilities for optimizing the machine tool, expanding the stability limits of processes, designing the machining process in a targeted manner and subsequently increasing the cutting performance by using stability maxima.

• DFG Programme: Research Grants
• Major Instrumentation: Spindelerweiterung
• Instrumentation Group: 2030 Fräsmaschinen