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Design and Safety Guidelines for Crossed Roller Bearings

by:JNSN     2021-12-29
Check the static load safety factor of crossed roller bearings. If the load distribution, end cover, position, fit and lubrication are known, we can calculate the static load safety factor that is closer to the true value, page 61, Figure 2. In order to check the static load safety factor, the parameters in the following equation need to be determined: ■ bearing load F0q ■ overturning moment M0q. Whether there is a radial force can be checked. If the load distribution is more complicated or the conditions are incomplete, please contact us. Safety factor For smooth operation, the result of safety factor fS 4, please refer to page 11. The method of calculating the rating life is: ■ The basic rating life L10 and L10h comply with ISO 281, please refer to page 12 ■ The simplified rating life calculation formula is based on empirical values, please refer to page 68. Validity The rated life formulas L and Lh are valid under the following conditions: ■ Load distribution according to page 61, Figure 2 ■ Both must meet the following conditions. Installation position (the inner and outer rings of the bearing must be firmly fixed with the surrounding structural parts), fit, and lubricate And sealing ■ The load and speed must be continuous during the working cycle. Simplified calculation method of rating life In order to obtain the rating life, a simplified formula can be used to calculate the rating life of a cross-roller bearing in a working cycle. In this working cycle, the load and speed are constant. The dynamic parameter fL is an empirical value for comparison with some new designs or existing SAMICK bearing arrangements. fL dynamic parameters, see table on page 70. Crossed roller bearings suitable for the machine tool industry: 3.5 fL 5C kN basic dynamic load rating fn For speed parameters, see page 69, table P kN equivalent dynamic bearing load. Calculation of equivalent dynamic load The equivalent dynamic load P is composed of the axial load and the radial load, please refer to the formula. For Fa/Fr 1.4: For Fa/Fr 1.4: Preload, main axial force Ka 2.114 · FV: Preload, main axial force Ka 2.114 · FV: Axial preload: P kN bearing equivalent Dynamic load Fr, Fa kN Bearing axial or radial dynamic load FV kN Preload, the recommended value is 3% of rated dynamic load CKa kN External axial force V mm Preload offset Cs kN0.926/mm axial For rigidity parameters, please refer to the size table. Shaft and housing tolerance The inner ring and outer ring of the bearing require a tight fit. In order to facilitate the installation and adjustment of the preload, the ferrule that bears the point load can adopt a looser tight fit. Crossed roller bearings used in the machine tool industry are generally inner rings. Therefore, the fit between the cross roller bearing and the shaft can be looser. When determining the diameter of the shaft and the bearing seat, the actual size of the inner and outer ring of the bearing needs to be used. The actual bearing size inspection report is attached to each bearing. The installation tolerance of the shaft is a loose fit because the inner ring is a point load. As a guide, the recommended clearance value for the shaft and inner ring of the bearing is, please refer to the formula and table. P m, fit clearance d mm shaft diameter. The mounting tolerance of the bearing seat is due to the cyclic load on the outer ring, which requires a tight fit. When machining the bearing seat hole, ensure the following interference, please refer to the formula and table. P m fit, interference fit D mm bearing seat bore. The roughness of the bearing mating surface The surface roughness of the bearing mounting surface needs to match that of the bearing. The average roughness Ra should not be too large to ensure the smallest reduction in interference. The shaft needs to be ground, and the bearing seat hole needs to be fine-turned. For guidance values, please refer to the table. The roughness guide value of the bearing mounting mating surface 1) The roughness grades in the table conform to DIN ISO 1302. The end cover fixation proves that the end cover or the sealed end cover is an effective method for fixing the cross sub-bearing. The inner and outer rings of the bearing must be sufficiently and evenly supported throughout the thickness and circumference. The thickness of the end cover and flange must meet the required value. Mounting bolts for fixing of bearing rings and end covers, bolt grade 10.9 is suitable. If the recommended size, grade and number of bolts are not used, the bearing capacity and life will be greatly reduced. For bolt grade 12.9, ensure the minimum force of the gland and use quenched and tempered gaskets. Anti-loosening of bolts Normally, the bolts will be safe enough under the correct preload. If there are frequent shock loads and vibrations, in this case, additional prevention of bolt loosening is required. Not every method of bolt loosening is suitable for crossed roller bearings. Do not use springs or open washers. Commonly used anti-loosening information for bolts can be found in DIN 25201, and anti-loosening through adhesives can be found in DIN 25203, 1992. If you need to use these, please contact the relevant Qingdao Ruijing Electromechanical Equipment Co., Ltd.
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