Views: 31 Author: Leapion Publish Time: 08-19-2022 Origin: https://www.leapion.com/
The guide rail system enables the machine tool to obtain a rapid feed rate. Under the condition of the same spindle speed, rapid feed is the characteristic of linear guides.
Linear guides, like plane guides, have two basic elements; one is a fixed element as a guide, and the other is a moving element.
Since the linear guide is a standard component, it is very important for machine tool manufacturers. The only thing to do is to machine a plane for the mounting rails and adjust the parallelism of the rails.
Of course, to ensure the accuracy of the machine tool, a small amount of scraping off the bed or column is essential, and in most cases, the installation is relatively simple.
Compared with flat guide rails, the geometry of the cross-section of linear guide rails is more complicated than that of flat guide rails. The reason for the complexity is that grooves need to be machined on the guide rails to facilitate the movement of sliding elements. The shape and number of grooves depend on the machine tool to be completed. function.
For example, a guide rail system that bears both linear force and subversion moment is compared with a guide rail that only bears linear force. There is a big difference in design.
There is no intermediate medium between the moving element and the fixed element of the linear guide, but rolling steel balls.
Because the rolling steel ball is suitable for high-speed movement, small friction coefficient, and high sensitivity, it can meet the working requirements of moving parts, such as tool rests of machine tools, carriages, etc.
The basic function of the fixed element (guide rail) of the linear guide system is like a bearing ring, a bracket for installing the steel ball, and the shape is a "V" shape.
The brackets wrap around the top and sides of the rails. To support the working parts of the machine tool, a set of linear guides has at least four brackets. For supporting large working parts, the number of brackets can be more than four.
When the working parts of the machine tool move, the steel balls circulate in the groove of the bracket, and the wear amount of the bracket is distributed to each steel ball, thereby prolonging the service life of the linear guide.
To eliminate the gap between the bracket and the guide rail, the preload can improve the stability of the guide rail system, and the preload can be obtained. It is to install an oversized steel ball between the rail and the bracket.
The diameter tolerance of the steel balls is ±20 microns, and 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 balls.
If the force acting on the steel ball is too large, the steel ball will be subjected to preloading for too long, increasing the movement resistance of the bracket.
There is a balance problem here; to improve the sensitivity of the system and reduce the movement resistance, the preload should be reduced accordingly, and to improve the movement accuracy and precision retention, it is required to have enough preload negative numbers, which are contradictory two. aspect.
If the working time is too long, the steel ball begins to wear, and the preload acting on the steel ball begins to weaken, resulting in the reduction of the movement accuracy of the machine tool parts.
If the original accuracy is to be maintained, the rail brackets must be replaced, or even the rails. If the rail system is already preloaded. System accuracy has been lost and the only way to do it is to replace the rolling elements.
The design of the rail system strives to have the largest contact area between the fixed element and the moving element,
This can not only improve the bearing capacity of the system, but also the system can withstand the impact force generated by intermittent cutting or gravity cutting, spread the force widely, and expand the bearing area.
To achieve this, the groove shapes of the guide rail system are various, and there are two representative ones. One is called the Gendai type (pointed arch type), and the shape is the extension of the semi-circle, and the contact point is the apex; One is a circular arc, which can also play the same role.
No matter what kind of structure, the purpose is only one, and strive to make more rolling steel ball radius contact with the guide rail (fixed element). What determines the performance characteristics of the system is how the rolling elements come into contact with the guides, which is the crux of the matter.
