Method of drive-integrated damping of spindle vibrations in machine tools

• Applicants: Professor Dr.-Ing. Berend Denkena; Professor Dr.-Ing. Bernd Ponick
• Subject Area: Metal-Cutting and Abrasive Manufacturing Engineering
• Term: from 2009 to 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 112455566

The productivity of milling processes is often limited by the dynamic properties of the machine tool and especially the spindle, as chatter vibrations usually occur even before the power capacity of the drive or the mechanical limit of the cutter material is reached. Beside defective surface quality of the machined workpieces, chatter vibrations can lead to severe workpiece or machine damage. To reduce the occurring vibrations in the spindle and therefore increase the productivity of the process, a motor spindle with a novel drive to create the torque as well as radial electromagnetic damping forces directly on the spindle shaft, is researched. The proposed method has been implemented and analyzed in a spindle prototype with an integrated electromagnetic actuator within the spindle drive. On the one hand, significant increase in the process stability can be achieved with the proto-type. On the other hand, the system dynamics change continuously with the use of different tools or tool holders and with the influence of the cutting process. Therefore, steady adjustments in the damping control of the actuator have to be carried out. So far, this has been done manually prior to the process. As the dynamics changed in the process, anew adjustment was necessary, so that the capacity of the method could not be exploited. Moreover, the integration of the extrinsic actuator into the drive causes losses in the available electrical spindle power. Accordingly, a fully integrated actively damped spindle prototype without extrinsic actuators will be developed in the project. This includes the development of a novel spindle drive to apply torque and radial damping forces. Fur-thermore, new methods for the automated, model-based parameterization of the damping control will be designed to maximize the process productivity regardless of the engaged tool or other changes in system dynamics.

• DFG Programme: Research Grants