When the working parts of the machine tool move, the steel ball circulates in the bracket groove, apportioning the wear amount of the bracket to each steel ball, thus extending the service life of the linear guide. In order to eliminate the gap between the bracket and the guide rail, preloading can improve the stability of the guide rail system. The preloading is achieved by installing oversized steel balls between the guide rail and the bracket. The diameter tolerance of steel balls is ± 20 microns. The steel balls are selected and classified in increments of 0.5 microns. They are respectively installed on the guide rails. The size of the preload depends on the force acting on the steel balls. If the force acting on the steel ball is too large and the preloading time is too long, the movement resistance of the support will be increased, and the balance problem will occur; In order to improve the sensitivity of the system and reduce the motion resistance, the preload should be reduced accordingly. In order to improve the motion accuracy and the retention of accuracy, it is required to have enough negative preload, which are two contradictory aspects.
If the working time is too long, the steel ball starts to wear, and the preload acting on the steel ball starts to weaken, leading to the reduction of the movement accuracy of the machine tool working parts. If the initial accuracy is to be maintained, the guide rail bracket must be replaced, or even the guide rail must be replaced. If the rail system has been preloaded. The system accuracy has been lost, and the feasible method is to replace the rolling element.
