Rigidity and lubrication of FAG cross roller bearings

Rigidity Due to the large number of cylindrical rollers, the bearings have high axial and radial load carrying capacity. The line contact between the roller and the raceway ensures that the bearing has a high rigidity, and after the mounting fit, the rigidity of the bearing will increase due to an increase in the preload. The axial deflection a of the FAG crossed roller bearing can be obtained by the following formula under the action of the axial force Ka through the shaft. Axial offset When Ka 2. 2.114 F FV: Axial offset When K 2.114 F FV: a a mm Axial offset between shaft ring and raceway Ka kN Internal axial force FV kN Bearing preload Cs kN0. 926/mm axial stiffness parameter. The calculation can only give the offset of the bearing and the offset of the peripheral structure must also be considered. Sealed bearings are open type. Some seals can be designed on the perimeter structure.

  Lubricated cross roller bearings can be lubricated with oil or grease. Grease lubrication For grease lubrication, high quality lithium grease KP2N–20 to DIN 51825 is suitable, eg Arcanol MULTITOP. For low speeds, especially horizontal shafts, simple grease lubrication can be used. For vertical shaft grease lubrication, install a baffle under the SKF bearing to prevent grease leakage. It is recommended to use lithium grease with EP additives. When adding grease, add some grease to the space between the rollers. The amount of relubricant is 20% to 30% of the initial amount of grease. Oil lubrication For oil lubrication, Lubricating Oil CLP in accordance with DIN 51517 or HLP in accordance with DIN 51524 Viscosity ISO VG 46 to ISO VG 68 is suitable. Cycling oil lubrication In general, the cross-roller circulating oil can be shared with the drive system. If only used for bearing lubrication, only a small amount of lubricant is needed. For high speeds, oil cooling is required and a large amount of lubricant is required, Figure 5. For each operating condition, the final actual amount of oil required is determined by the bearing temperature. V = oil volume D = bearing outside diameter a = sufficient oil quantity for lubrication b = required oil quantity for cooling and lubrication Lubrication and cooling ?

  The reference viscosity of mineral oil in order to ensure adequate lubrication The dynamic viscosity of the lubricant for NTN bearings is determined by the reference viscosity ?1. In this case, ensure that the working viscosity of the lubricant (viscosity at operating temperature) is at least equal to the reference viscosity ?1. The ratio ? = ?/?1 = 2, Figure 6. The reference viscosity is determined by the average bearing diameter dM = (D + d)/2 and the speed. Viscosity at work? You can use the “Viscosity/Temperature” table to find the reference temperature and the viscosity at +40 °C. Lubricants with a working viscosity greater than 1 at operating temperature have a positive effect on bearing fatigue life. In addition, bearings with EP additives ensure adequate lubrication at low speeds. EP additives are also needed at lower levels. Operating temperature The cross-roller bearing has a suitable operating temperature range of –30 °C to +80 °C. n = working speed 1 = reference viscosity dM = diameter of the bearing (d + D)/2 = working temperature Viscosity mm2s–1 at +40 °C Figure 6 Reference viscosity and V/T of mineral oil.