What are the characteristics of linear guide

Linear guides, also known as line rails, slides, linear guides, linear slides, are used in linear reciprocating motion occasions. They have a higher rated load than linear bearings, and can bear a certain amount of torque. They can achieve high-precision linear motion under high load conditions.

The function of linear motion guide is to support and guide the moving parts, and to make reciprocating linear motion in a given direction. According to the nature of massage 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 automation machinery, such as machine tools imported from Germany, paper bowl machines, laser welding machines and so on. Of course, linear bearings and linear shafts are matched. Like linear guides are mainly used in mechanical structures with high accuracy requirements.

Slider - Change motion from curve to straight line. The new guideway system enables the machine tool to obtain fast feeding speed. Under the same spindle speed, fast feeding is the characteristic of linear guideway. Like planar guides, linear guides have two basic elements: one is fixed element as guide, the other is mobile element. As the linear guide is a standard component, the only thing for the machine tool manufacturer to do is to process a plane to install the guide and adjust the parallelism of the guide. Of course, in order to ensure the accuracy of the machine tool, a small amount of scraping and grinding on the bed or pillar is essential. In most cases, the installation is relatively simple.

The guide rail is hardened steel and is placed on the installation plane after fine grinding. Compared with planar guides, the geometric shape of cross section of linear guides is more complex than planar guides. The reason is that grooves need to be machined on the guides to facilitate the movement of sliding elements. The shape and quantity of grooves depend on the functions of machine tools. For example, the design of a rail system that bears both linear force and overturning moment is quite different from that of a guide system that only bears linear force.

Rolling steel balls are used instead of intermediate between moving and fixing elements of linear guideways. Because rolling steel ball is suitable for high-speed movement, small friction coefficient and high sensitivity, it meets the working requirements of moving parts, such as tool holder, trailer, etc. The basic function of the fixed element (guideway) of the linear guideway system is like a bearing ring, a bracket with a steel ball mounted in the shape of "v". The bracket covers the top and sides of the guide rail. In order to support the working parts of the machine tool, a set of linear guides has at least four supports. For supporting large working parts, the number of supports can be more than four.

When the working parts of the machine tool move, the steel balls circulate in the trench of the support, which distributes the wear amount of the support to each steel ball, thus prolonging the service life of the linear guide rail. In order to eliminate the gap between the support and the guide rail, the preload can improve the stability of the guide rail system and obtain the preload. It is to install extra-sized steel balls between the guide rail and the support. The diameter tolerance of the steel balls is (+20 micron), and the balls are screened and classified by 0.5 micron increment. 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 endure the preload for too long, which will lead to the increase of the bracket resistance. There is a balance problem here; in order to improve the sensitivity of the system and reduce the resistance of motion, it is necessary to reduce the preload accordingly. In order to improve the accuracy and accuracy of motion, it is necessary to have enough negative preload, which is contradictory in two aspects.

When the working time is too long, the steel ball begins to wear, and the preload acting on the steel ball begins to weaken, which leads to the reduction of the motion accuracy of the machine tool working parts. If the initial accuracy is to be maintained, the guide bracket must be replaced or even the guide rail must be replaced. If the guide rail system has pre-loaded effect. The accuracy of the system has been lost. The only way is to replace the rolling elements.

The design of guideway system strives to maximize the contact area between fixed and mobile components, which can not only improve the bearing capacity of the system, but also withstand the impact force produced by intermittent cutting or gravity cutting, so that the force can be widely spread and the bearing area can be enlarged. In order to achieve this, the groove shape of the guideway system has many kinds, there are two representative types, one is called Gothai type (pointed arch type), the shape is the extension of the semi-circle, the contact point is the vertex; the other is the circular arc, which can also play the same role. No matter which type of structure, there is only one purpose to make more contact between rolling ball radius and guide rail (fixed element). The key factor to determine the system performance characteristics is how the rolling element contacts the guide rail, which is the key to the problem.