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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.

Ball bearings failure analysis using vibrations is widely researched. Bearings are main part of rotary machines that work for years if they work in a proper situation. Fluting occurs in a drive motor bearing and driven machine's bearings because of current discharge from variable frequency drive motors to the bearings by transferring from the shaft and coupling to the bearings. In this research, spherical roller bearing is analyzed. Envelope and spectrum analysis is used to show what occurs when stray current flows to the gearbox bearings by passing through shaft and coupling. Fluting response in vibrations by using envelope and spectrum is shown. This paper shows how ball pass frequency inner race, ball pass frequency outer race with fundamental train frequencies side bands are excited in the natural frequencies area or high frequencies by stray current at the first time of running before bearing failed. [ABSTRACT FROM AUTHOR]

Abstract: A technique of determining the onset of preload loss in a ball screw feed drive system via monitoring the change of ball pass frequency is proposed. The ball pass frequency of a ball screw with preload is smaller than that of ball screw without preload due to friction caused by the preload. Results from both simulations and experiments show that the ball pass frequency can be detected using the method of Angular Velocity Vold–Kalman Filtering Order Tracking (AV VKF-OT). And AV VKF-OT provides a much better performance as compared to the traditional order tracking in terms of resolution and accuracy. Tests were conducted on ball screw feed drive systems with different preloads for the performance assessment of the ball pass frequency detection. Results show that the preload loss increases the ball pass frequency and also induces the side band around the ball pass frequency, which provides promising criteria in detecting the onset of preload loss of ball screws. [Copyright &y& Elsevier]