Novel Method for Selective and Controlled Online Mass Removal Using Laser Beam for In Situ Balancing of Flexible Rotor Bearing System

Balancing flexible rotors is a tedious process as compared to rigid rotor bearing systems due to shaft bending. Flexible rotors are allowed to run near their bending critical speeds and (stops) prevent the system from balancing from correction planes. Prediction of unbalance accurately has been the topic of research for a long time. To avoid the difficulties of present time-consuming balancing procedures, a new methodology was developed to balance rigid and flexible rotors. This paper presents a new methodology where in situ balancing is possible to perform by removal of mass from the rotor which is running in vacuum using a LASER beam. An experimental test setup was developed to demonstrate the mass removal from an overhung flexible rotor, which is running in vacuum. An electronics system for the measurement of position and synchronization of the LASER beam with the rotor speed is demonstrated. The method of generation of synchronization pulse and desired arc so as to fire the LASER beam in synchrony with the rotating disc is also explained. The system trial with various operating speeds is conducted and the quantity of mass removal and resolution is calculated. The experimental results are also presented with the identification of critical issues to be addressed for application in actual rotor systems for in situ balancing.