Vibration control of an NC lathe by variable frequency damper

Vibration control of feed table on NC positioning control is one of the most important problems in machine tools, because the amplitude of vibration itself causes the degradation of machined profiles and surface roughness. Previous studies have been looked at the low frequency range in which conventional NC feed table responds and deal with the vibration problem while positioning. Another vibration problem exists in the range of same frequency. The phenomenon is often caused by the locking motion and the rigidity of ball-screw driving mechanism. Therefore, conventional vibration control method by computing input command that compensates the positioning accuracy is not to be adapted. The variable frequency passive damper is designed based on the measurement results of dynamic characteristics on the positioning system and developed in order to solve this problem. The effects of the damper are reported with experimental testing and calculation results of the parameters.