What are the classifications of the guide rails of CNC machine tools? What are the characteristics of different guide rails?

2019-12-23 15:11:33

The performance of the machine guide rail directly affects the machining accuracy, load bearing capacity and performance of the machine tool. Therefore, the guide rail should meet the following basic requirements: simple structure, good guiding precision, precision retention, low speed motion stability and good maneuverability. It is understood that the guide rail is an important part of the feed system. Different types of machine tools have different requirements on the guide rails.

The guide rails of CNC machine tools are higher than the guide rails of ordinary machine tools: no vibration occurs during high-speed feed, no creep phenomenon occurs during low-speed feed, high sensitivity, good wear resistance, continuous operation under long-term heavy load, precision retention Wait a minute. When the machine tool user selects the machine tool, the machine tool guide is selected according to the above requirements according to the above requirements. Common guide rails for machine tools are sliding guides, rolling guides and hydrostatic guides.

1 sliding guide

The sliding guide rail has the advantages of simple structure, convenient manufacture, good rigidity and strong shock resistance. It is most widely used in general machine tools, and is often made of cast iron or steel guide rails. In order to improve the wear resistance and accuracy of the guide rail, the surface of the guide rail is generally quenched and then ground.

2 rolling guide

The rolling guides are arranged with rolling elements between the working faces of the guide rails. The rolling elements can be balls, rollers and needles. The contact with the guide rails is point contact or line contact, so the friction coefficient of the guide rails is small. The dynamic and static friction coefficients are basically the same, the starting resistance is small, the low speed movement is good, the positioning accuracy is high, the micro displacement is accurate, the wear is small, the precision retention is good, and the service life is long. The disadvantage is that the shock resistance is poor and the protection requirements are high. Rolling guides, especially linear rolling guides, have been widely used in recent years. With the development of high-speed CNC machine tools, linear guides are becoming more and more widely used.

3 hydraulic rail

The hydraulic guides used on machine tools are mainly hydrostatic guides. Hydrostatic rails typically pass pressure oil between two relatively moving rail faces to cause the moving parts to float. The oil pressure can be automatically adjusted according to the change of the applied load to ensure that the frictional state of the pure liquid is always between the rail surfaces. Therefore, the static pressure rail has the smallest friction coefficient and low power consumption. The guide rail is not easy to wear, and the precision of the guide rail is good and the service life is long. Its oil film thickness is almost unaffected by speed. The oil film has large bearing capacity, high steel absorption and good shock absorption, stable operation and no creeping phenomenon. The hydrostatic guide rail has a complicated structure and requires a hydraulic device with a good filtering effect, and the manufacturing cost is high.