FAG Crossed Roller Bearings Design and Safety Guide

Testing FAG Crossed Roller Bearing Static Load Safety Factor If the load distribution, end cap, position, fit, and lubrication are known, we can calculate the static load safety factor that is closer to the true value, p. 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. The radial force can be checked. If the load distribution is more complicated or the conditions are incomplete, please contact us. Safety factor In order to operate smoothly, the result of safety factor fS ? 4, see page 11. Rated life calculations The method for calculating the rated life is: ■ The basic rating life L10 and L10h comply with ISO 281, see page 12 ■ The simplified rating life calculation formula is based on empirical values, see page 68.

Effectiveness Nominal life formulas L and Lh are valid under the following conditions: ■ Load distribution according to page 61, ■ Both must meet the following conditions for mounting position (The inner and outer ring of the bearing must be fastened to the surrounding structural parts), Mating, lubrication and sealing ■ The load and speed must be continuous during the work cycle.


  Simplified calculation method for rated life In order to know the rated life, a simplified formula can be used to calculate the rated life of a crossed roller bearing in one working cycle. In this work 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 page 70, table. Cross roller bearings for the machine tool industry: 3.5 ? fL ? 5C kN basic dynamic load rating fn - speed parameter, see page 69, table P kN bearing equivalent dynamic load. Calculation of Equivalent Dynamic Load The equivalent dynamic load P is composed of axial load and radial load. See 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, Recommended value is 3% Rated dynamic load CKa kN External axial force V mm Preload offset Cs kN0.926/mm Axial Rigid parameters, see the dimension table.

  Shaft and housing tolerances The inner and outer rings of the bearing require a tight fit. For the convenience of installation and adjustment, the ferrule bearing the point load can be loosely fitted. IKO cross roller bearings for the machine tool industry are generally inner rings. Therefore, the cross roller bearing and the shaft can be loose. When determining the diameter of the shaft and housing, the actual dimensions of the inner and outer rings of the bearing need to be used. The actual bearing size inspection report is attached to each bearing. Shaft installation tolerances Because the inner ring is a point load, it is a loose fit. As a guide, it is recommended that the shaft and the bearing inner ring cooperate with clearance values, see formulas and tables. P ?m, with the amount of clearance d mm shaft diameter. Bearing tolerances of the housing because the outer ring is subjected to a cyclic load, which requires a tight fit. When machining the housing bores, the following interferences must be guaranteed. See formulas and tables. P mm fit, interference fit D mm bearing seat bore.

  Roughness of the bearing mating surface The surface roughness of the bearing mounting surface needs to match the bearing. The average roughness Ra cannot be too large to ensure that the reduction in the amount of interference is minimal. The shaft needs to be ground and the bearing seat hole needs a finishing car. For guide values, see the table. Roughness guidelines for bearing mounting mating surfaces 1) The roughness level in the list complies with DIN ISO 1302. End cap fixation Certified end caps or sealed end caps are an effective method for securing cross-section bearings. The inner and outer rings of the bearing must have sufficient uniform support throughout the entire thickness and circumference. The thickness of the end caps and flanges must meet the required values. Mounting Bolt Bearing rings and end caps are fixed. Bolt level 10.9 is suitable. If you do not use the recommended size, grade and number of bolts, bearing capacity and life will be greatly reduced. For bolt grade 12.9, ensure minimum gland force and use tempered shims. Locking of bolts Normally, the bolts are sufficiently safe under the correct preload. If there is frequent impact load and vibration, in this case, extra bolts need to be prevented from loosening. Not every kind of bolt loosening method is suitable for cross roller bearings. Do not use springs or open washers. The usual anti-loosening information for bolts can be found in DIN 25201. Loose-proofing with adhesives can be found in DIN 25203, 1992.