Dynamic signal analysis based monitoring for ball screws preload deterioration

The ball screw feed system has been an important part of precision machinery and machine tools. Its preload degradation affects machining accuracy and the issue should be first coped with per manufacturers’ suggestion. The study aims to apply the adaptive order tracking technique and other spectrum analysis schemes as well to differentiate the preload conditions of ball screws. Here varied preload conditions (4 %, 1 % preload and 12um backlash) were considered for monitoring during normal operation. The sideband energy of higher harmonics of ball pass frequency (BPF) are featured to highlight the preload degradation. The control charts together with sideband ratios were established to differentiate preload conditions and single out backlash ball screws.