Views: 106 Author: Leapion Publish Time: 05-29-2023 Origin: https://www.leapion.com/
Linear guides, also known as line guides, slide rails, linear guide rails, and linear slide rails, It is used in linear reciprocating motion applications and has a higher rated load than linear bearings, At the same time, they can bear a certain torque and realize high-precision linear motion under high load conditions.
The function of the linear motion guide rail is to support and guide the moving parts and perform reciprocating linear motion in a given direction. According to the nature of friction, linear motion guides can be divided into sliding friction guides, rolling friction guides, elastic friction guides, fluid friction guides, and other types. Linear bearings are mainly used in automated machineries, such as machine tools imported from Germany, paper bowl machines, laser welding machines, etc. Of course, linear bearings and linear shafts are used together. The linear guides are mainly used for high precision requirements. on the mechanical structure.
The slider transforms the motion from a curve to a straight line. The new guide rail system enables the machine tool to obtain a rapid feed rate, which is the characteristic of linear guides when the spindle speed is the same. Linear guides have the same two basic elements as flat guides; one is a fixed element as a guide, and the other is a moving element. Since the linear guide is a standard component, For machine tool manufacturers. The only thing to do is to machine a plane for the mounting rail and adjust the parallelism of the rail. Of course, to ensure the accuracy of the machine tool, a small amount of scraping off the bed or column is essential. In most cases, the installation is relatively simple.
The guide rail is made of hardened steel and is placed on the mounting surface after fine grinding. 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 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 motion, small friction coefficient, and high sensitivity, it can meet the working requirements of moving parts, such as machine tool rests, 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 beam of the machine moves, the steel balls circulate in the groove of the bracket, and the wear of the beam is distributed to each steel ball, thereby prolonging the service life of the linear guide. To eliminate the gap between the beam 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 oversized steel balls between the guide rail and the beam. 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 beam. 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 is contradictory.
If the working time is too long, the steel ball begins to wear out, and the preload acting on the steel ball begins to weaken, resulting in the reduction of the movement accuracy of the machine beam. 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 guide rail system strives to have the largest contact area between the fixed element and the moving element, which 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 capacity. area of force. To achieve this, the groove shapes of the rail system have various shapes, and there are two representative ones. One is called the Goda type (pointed arch type), the shape is the extension of the semicircle, and the contact point is the vertex; the other species is arc-shaped and 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.
