Identification of the operating conditions of main spindle bearings reducing the service life on the basis of the acting dynamic load at the cutting edge contact point (DynaLast)

 

Description of the research project The previous design of spindle systems and the investigation of the operating and wear behaviour of spindle bearings are only carried out under the assumption of static loads. The influence of dynamic process loads was not investigated. The aim of the project is therefore to identify the service life reducing operating conditions of main spindle bearings on the basis of the acting dynamic load at the cutting edge contact point.

At the beginning of the project, the actual bearing loads are determined in real milling processes. Finally, these quantities are used to model the spindle system for calculating external and internal bearing loads based on the spindle dynamics and the kinematic properties of the spindle bearings.

Within the scope of the project, two identical test rigs will be developed and manufactured, which allow a process-like loading of the spindle systems. The dynamic load of the rotating spindle shaft and the measuring method for determining the bearing loads are the focus of the activities. The load on the spindle can be based on real process loads in radial and axial direction, both in the swelling and in the changing load range.

During the subsequent test bench investigations, the test spindles are operated in endurance tests until the end of the bearing service life. To better identify operating conditions that reduce the service life, the spindle is subjected to purely harmonic loads in the range of the natural frequencies of the spindle system in initial series of tests. In the following, real process loads are mapped to evaluate the influence of a complex load condition. Accompanying the test bench investigations a correlation analysis between the introduced dynamic loads and the observed bearing failure mechanisms is carried out. This procedure allows the answer to the research topic which deals with the identification of operating conditions of main spindle bearing arrangements which reduce the service life.