As one of the critical components in machinery, the health monitoring of ball screws has attracted significant attention. Numerous industrial machines have benefited from the application of ball screws, such as high-precision leveling control systems in aircraft and feed drive systems in machine tools. The health status of a ball screw depends on monitoring its preload condition. Preload failure affects positioning accuracy; under long-term high-speed and heavy-load operation, friction between the balls, screw shaft, and nut grooves causes wear. Loss of preload leads to backlash and lost motion, reducing positioning accuracy. Ball screws used in industrial machinery (Figure 1) convert rotary motion into linear motion, featuring high precision and efficiency. Backlash caused by manufacturing gaps or deflection from external forces can be eliminated by applying preload. Preload can be achieved through double-nut spacers, offset lead single nuts, or adjusting ball sizes. Insufficient preload reduces rigidity and may cause idle motion, while excessive preload increases friction torque and heat generation, shortening the ball screw’s lifespan. Therefore, appropriate and constant preload is essential for maintaining positioning accuracy and reliability. Wear during prolonged operation reduces preload, degrading positioning accuracy. Detecting preload loss is thus a critical issue, especially for high-speed and high-precision machines. Based on these industrial needs, NCU’s Sensing, Monitoring, and Diagnostic Evaluation Laboratory is dedicated to developing fault diagnosis and condition monitoring methods for ball screws.

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