The measurement of the accuracy of the rotation coordinate of a CNC machine tool can be carried out using a polyhedral prism combined with a laser interferometer when the rotation coordinate can be rotated by 360°. When the rotation coordinate cannot be rotated by 360°, an inclinometer or a circular grating (or angle Encoder), and then make necessary adjustments and control parameter compensation to the corresponding transmission system, bearing support system, etc., to obtain the ideal transmission accuracy. The accuracy assessment of the rotary coordinates of CNC machine tools is generally divided into positioning accuracy, repeat positioning accuracy, and reverse error. From the analysis of the principle of closed-loop transmission of CNC machine tools, the main causes of errors are the feedback accuracy of the closed-loop circular grating (or angle encoder), the indexing accuracy of the transmission system, the backlash of the transmission link, the matching error of the rotary shaft, the supporting bearing and The result of the combined effect of factors such as the radial runout of the rotating parts and the center of rotation (the distance from the center of rotation of the rotating coordinate to the end face of the spindle).
Among them, the error factors of feedback components, transmission pairs and support bearings can be effectively solved by selecting components with higher accuracy levels. The radial runout errors of rotating parts can be guaranteed by more stringent mechanical manufacturing processes. These error factors can only rely on Machine tool manufacturers can effectively avoid the corresponding increase in production costs.
The fit error of the rotary axis must be solved by a more suitable fit tolerance and proper bearing pre-tightening, but over-tightening and too large pre-tightening will cause additional power loss in the rotary motion, and make the machine tool’s rotary axis start without load. The increased torque affects the dynamic performance of the machine tool. In order to obtain a good running state for the rotating coordinates of a CNC machine tool, sufficient test verification must be carried out to obtain a suitable matching accuracy and a suitable bearing preload for the rotating support shaft. The five-axis linkage error caused by the inaccurate measurement of the center of rotation is too large. The value of the center of rotation can be corrected and the five-axis linkage accuracy test and verification can be repeated to obtain an accurate center of rotation. The movement error of the rotary coordinate of the CNC machine tool is caused by the transmission link. The main factors are the unevenness of the transmission system and the inaccurate positioning, and the excessive backlash leads to the low repeat positioning accuracy and large reverse error. The indexing accuracy of the drive train can be ensured by improving the accuracy of the relevant transmission elements; the backlash must be adjusted to the relevant mechanical structure.
In summary, a set of crossed roller bearings can withstand axial, radial and overturning moment loads with appropriate preload, thereby reducing the error factor of the supporting bearing. With the widespread application of CNC machine tools in recent years, the superiority of the indexing mechanism using a single set of cross roller bearings as supporting bearings has been generally recognized.
Crossed cylindrical roller bearings are also called crossed roller bearings. The rolling elements are generally cylindrical rollers or tapered rollers arranged in a cross on a single raceway. The rollers are separated by cages or spacers. It has high rotation accuracy, large bearing capacity, small size, high rotation speed and rigidity, and has a wide range of uses. Suitable for industrial robot joints, CNC turntables, DD motors, medical equipment and other fields.
In terms of structure, the structure of crossed roller bearings is much simpler than that of traditional bearings. With a single row of cross-arranged cylindrical rolling elements, considerable axial and radial bearing capacity and overturning moment can be obtained. The structure is relatively simple. Traditional bearings must be arranged in sequence through multiple sets of bearings to achieve the same effect, which brings great convenience in terms of design, assembly and installation. Compared with traditional bearings, the space occupied by the equipment is much smaller, and the assembly difficulty is greatly reduced.
In terms of installation, the installation of crossed roller bearings is more convenient, and the mechanism design tends to be simplified. The crossed roller bearings RU series, XU series, and XSU series cross roller bearings have increased mounting hole designs, making their installation and use easier. Greatly simplified the structure of the turntable and optimized its performance.
In terms of maintenance, the outer ring of the crossed roller bearing is designed with lubricating holes and oil grooves, which is convenient for lubrication. It uses lithium-based extreme pressure grease and does not require frequent grease replacement. It is a series of guarantees for the stability and life of the bearing. ; If the speed of the turntable is required to be high, it can also be designed for circulating oil lubrication, which can effectively prevent the aging of the lubricating oil caused by the heating of the bearing, and can effectively discharge the wear debris in the friction pair while discharging more heat. Recycling, and can ensure the bearing to work at a lower temperature, which is beneficial to delay the friction and wear of the bearing and prolong the service life of the bearing.
In summary, TEDIN’s cross roller bearings are suitable for precision CNC turntables, indexing plates, tool magazine ATC devices, multi-axis turntables, welding multi-station turntables, automatic line turntables, grinding and polishing machine turntables, medical turntables, Application in various fields such as measuring equipment turntable.
Please check the Product Guide to select suitable bearings for your machinery.
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