Condition Monitoring of Ball-Screw Drives Based on Frequency Shift

Ball-screw drives are one of the common wear parts in machine tools. The wear will affect the positioning accuracy of motion axes and can cause a high rejection rate in production. Therefore, it is interesting to develop a method, which can detect the wear condition of ball screws at an early stage. Stiffness loss and backlash in ball-screw drives are often associated with wear. This article proposes a novel method to detect stiffness loss and backlash for ball-screw drives without preload based only on machine internal data. To simulate the wear of a ball screw, a spacer sleeve has been designed, which effectively reduces the axial stiffness of the feed axes. This design allows a quick modification of the wear status of the machine axes and can be utilized to test if the wear status is detectable by analyzing the machine internal data. A multimass model is developed and validated by experimental data, which is used to simulate the dynamic behavior of the machine axis dependent on wear.