An important feature of friction printing press bearings is that the friction torque is small and the operating temperature is low. Generally, the operating temperature of the bearing should not exceed +60 C to prevent adverse effects on the printing process. Cylindrical roller bearings have very little friction and are therefore conducive to high-speed operation of the printing press. Influencing factors The friction torque and temperature rise of a bearing are influenced by the following important factors: ■ Bearing type ■ Bearing size ■ Speed u200bu200b■ Load ■ Bearing clearance ■ Lubrication ■ Application ■ Sealing. Lubrication has a considerable effect on the operating temperature of the bearing. The use of special grease with excellent performance can greatly reduce the operating temperature of the bearing compared to when it is lubricated with oil. Based on practical experience, the reference value of the working temperature of the main roller bearing arrangement is given, see the table. When lubricating with grease at operating temperature, it must be ensured that there is not too much grease in the bearing, especially for three-ring and four-ring cylindrical roller bearings. Otherwise, due to the increase in lubricating agitation, the temperature of the bearing must be much higher in the first few hundred hours of operation of the high-speed offset press. Therefore, the amount of grease for initial lubrication and relubrication must be carefully determined according to the type of bearing. We recommend consulting the engineering services department of the Schaeffler Group. Friction and Temperature Rise Friction Calculation In order to determine the friction value, the speed and load must be known. In addition, the type of lubrication, the method of lubrication and the viscosity of the lubricant at operating temperature are also necessary factors in the calculation. The friction and friction energy of printing press bearings with working clearance can be calculated approximately. Total frictional torque MR: Frictional power NR: Speed-dependent frictional torque n 2 000: Speed-dependent frictional torque n 2 000: For cylindrical and double row tapered roller bearings, load-dependent Friction torque (in printing presses, tapered roller bearings mainly bear radial load): MR Nmm Total friction torque M0 Nmm Speed-related friction torque M1 Nmm Load-related friction torque NR W Friction power n min1 Working speed f0 for Bearing factors for the calculation of the friction torque in relation to the rotational speed, see page 21, table mm2s1 Kinematic viscosity of lubricants at operating temperature. The viscosity of the grease depends on the viscosity of the base oil at operating temperature dM mm average bearing diameter (d + D)/2f1 Bearing factor for load-dependent friction torque calculation, see page 21, table FN for radial bearings It is the radial load that it bears, and it is the axial load that it bears for the thrust bearing. Bearing factors Bearing factors f0 and f1 are average values u200bu200bobtained from a series of tests in accordance with ISO 15312, see table. For grease lubrication, these data are valid only after running in and for bearings with an even distribution of lubricant. For freshly charged grease, the bearing factor f0 should be increased by a factor of 2 to 5. For oil bath lubrication, the oil level must reach the centerline of the lowest rolling element. If the oil level is too high, the value of f0 may reach 3 times the table data. Bearing coefficients of cylindrical roller bearings with cages Bearing coefficients of thrust roller bearings Bearing coefficients of tapered roller bearings Bearing coefficients of preloaded printing press bearings In bearings with preloaded rolling elements, the rolling elements are subject to additional loads. Depending on the preload, an increase in the friction torque may result.