Vibration analysis milling machine

The project task was to shut down a milling machine due to the permissible load on the drive motors being exceeded as a result of loosening attachments and broken bolts. A vibration problem was suspected because of the loosening and breakage of the bolts. As a result, the task was to determine the natural frequencies of the entire system.

The natural frequency analysis of the milling system consisting of table, portal and milling unit showed frequencies of the table and portal between 20 and 40 Hz. In contrast, acceleration measurements on the milling unit showed excitation frequencies of 1-2 Hz. The simulation of the milling unit showed a natural frequency of 1.79 Hz!

By changing the design of the base plate of the motor mounting, the natural frequencies could be increased to > 15 Hz. This tenfold increase in the natural frequency solved the problem. The system now runs smoothly and without any failure of the bolt connections.