The working principle of the linear guides

The working principle of the linear guide can be understood as a kind of rolling guidance, which is an infinite rolling cycle between the sliding block and the guide rail by the steel ball, so that the load platform can easily move along the guide rail with high-precision linear motion, and reduce the friction coefficient to one fiftieth of the ordinary traditional sliding guidance, which can easily achieve high positioning accuracy. The final unit design between the sliding block and the guide rail makes the linear guide rail bear the load in the up, down, left, right and other directions at the same time. The patented reflux system and refined and simplified structural design make the linear guide rail move more smoothly and with low noise.

Slider - converts motion from a curve to a straight line. The new guide rail system enables the machine tool to obtain rapid feed speed. When the spindle speed is the same, rapid feed is the characteristic of linear guide rail. Like plane guide rail, linear guide rail has two basic elements; One as a guide is a fixed element, and the other is a moving element. Since the linear guide rail is a standard part, the only thing for the machine tool manufacturer is to process the plane of an installation guide rail and adjust the parallelism of the guide rail. Of course, in order to ensure the accuracy of the machine tool, a small amount of scraping and grinding of the bed or column is essential. In most cases, the installation is relatively simple. The guide rail as a guide is hardened steel, which is placed on the installation plane after fine grinding. Compared with the plane guide rail, the geometry of the cross section of the linear guide rail is more complex than the plane guide rail. The reason for the complexity is that the guide rail needs to be processed with grooves to facilitate the movement of sliding elements. The shape and quantity of grooves depend on the functions to be completed by the machine tool. For example, the design of a guide rail system that bears both linear force and overturning moment is very different from that of a guide rail that only bears linear force.

The basic function of the fixed element (guide rail) of the linear guide rail system is like the bearing ring and the support for installing the steel ball, which is in the shape of "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 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 ball circulates in the support groove, apportioning the wear of the support to each steel ball, so as to prolong the service life of the linear guide rail. In order to eliminate the gap between the support and the guide rail, preloading can improve the stability of the guide rail system. The acquisition of preload is to install oversized steel balls between the guide rail and the support. The diameter tolerance of the steel ball is ± 20 microns. The steel ball is screened and classified in increments of 0.5 microns and installed on the guide rail 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 and the preloading time is too long, the movement resistance of the support will be enhanced, and the problem of balance 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 accuracy retention, sufficient preload negative numbers are required, which are two contradictory aspects.

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 motion accuracy of the working parts of the machine tool. 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 guide rail system has been preloaded. The system accuracy has been lost, and the only way is to replace the rolling elements.

The design of the guide rail system strives to have the maximum contact area between the fixed elements and the moving elements, 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, widely spread the force and expand the bearing area. In order to achieve this, the groove shapes of the guide rail system are diverse, and there are two representative ones. One is called Gothic (pointed arch), the shape is the extension of semicircle, and the contact point is the vertex; The other is circular arc, which can also play the same role. No matter which structural form, there is only one purpose, and strive to make more rolling steel ball radius contact with the guide rail (fixed element). The key factor determining the performance characteristics of the system is how the rolling element contacts with the guide rail.