In the era when the improvement of industrial automation, the high-performance ball screw, as a core precision transmission component of machine tools, plays a key role in various transmission devices.
In the application of ball screw pairs, applying a preload force to the nut is a key means to enhance its performance. This operation can significantly increase the axial stiffness of the ball screw assembly and greatly improve the positioning accuracy. Theoretically speaking, if we only focus on the stiffness and positioning accuracy of the ball screw kit, it seems that the greater the preload force, the more ideal the effect will be, because a larger preload force can more effectively eliminate the axial clearance caused by elastic deformation. However, the actual situation is not so simple. Even if a small preload force can temporarily eliminate the axial clearance, it is difficult to truly improve the overall stiffness of the ball screw pair.
This is because the preload force must reach a specific threshold to effectively eliminate the "low stiffness area" of the preloaded nut. In the double-nut preloading structure, parameters such as lead errors inevitably exist in the ball screw and nut components. This deviation will cause that when the screw shaft and nut come into contact, some areas will fit more closely after being deformed by force, resulting in a higher contact stiffness; while other areas will become relatively loose after deformation, forming a "low stiffness area" with a lower contact stiffness. Only when a sufficiently large preload force is applied to eliminate these "low stiffness areas" can the axial contact stiffness be effectively enhanced, achieving the goal of optimizing performance.
However, the preload force is not the larger, the better. An excessively large preload force will bring a series of negative impacts:
1. Significantly increase the torque required for driving, resulting in a decrease in transmission efficiency;
2. Intensify the contact fatigue and wear between the balls and the raceways, directly shortening the working life of the ball screw and ball nuts.
