The linear guide rail uses rolling steel balls instead of intermediate media between the moving element and the fixed element.
Because rolling steel balls are suitable for high-speed movement, low friction coefficient, and high sensitivity, they meet the working requirements of moving parts, such as the tool holder and carriage of machine tools.
The basic function of the fixed element (guide rail) of the linear guide rail system is like a bearing ring. The bracket for installing the steel ball is in the shape of a “V”. The bracket wraps the top and both sides of the guide rail. In order to support the working parts of the machine tool, a set of linear guide rails has at least four brackets. For supporting large working parts, the number of brackets can be more than four.
The diameter tolerance of the steel ball is ±20 microns. The steel balls are screened and classified in increments of 0.5 microns and installed on the guide rails respectively. The size of the preload depends on the force acting on the steel ball.
If the force acting on the steel ball is too large, the steel ball will be subjected to the preload for too long, resulting in increased resistance to the movement of the bracket. There is a balancing issue here;
In order to improve the sensitivity of the system and reduce the movement resistance, the preload should be reduced accordingly, while in order to improve the movement accuracy and accuracy retention, sufficient preload negative number is required, which are two contradictory aspects.