A novel method for vibration surveillance during high speed ball end milling of flexible details

The paper is devoted to vibration surveillance of unsteady systems, which are idealized by the finite element method. Ball end milling of flexible details is observed very frequently in case of modern machining centres. Tool-workpiece relative vibration may lead to a loss of stability and cause a generation of self-excited chatter vibration. The paper proposes the method of minimizing vibration level, based on matching the spindle speed to the optimal phase shift. As result of a milling process modeling, we get a hybrid system in which are separated: - Modal subsystem. It is a stationary model of one-side-supported flexible detail. - Structural subsystem, i.e. non-stationary discrete model of ball end mill and cutting process. - Connective subsystem as conventional contact point between tool and workpiece. The method has been developed with success. Modal model of the workpiece allowed us to determine an optimal spindle speed. Modal assurance criterion (MAC) has been assessed and confirmed good agreement between experimental and theoretical modal model. Results of computer simulation, as well as - of experimental investigation on the Mikron VCP 600 milling machine mean to be in support. Hence amplitude values for chosen optimal spindle speed became relatively smaller than for the other ones.