An important feature of friction printing machine bearings is the low friction torque and low operating temperature. 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, so they are conducive to high-speed printing presses. Influencing factors The friction torque and temperature rise of the bearing are affected by the following important factors: ■ bearing type ■ bearing size ■ speed ■ load ■ bearing clearance ■ lubrication ■ application ■ sealing. Lubrication has a considerable influence 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 with oil lubrication. Based on practical experience, the reference value of the working temperature of the main roller bearing arrangement is given, see the table. When using grease lubrication at working temperature, it is necessary to ensure that the grease in the bearing cannot be too much, especially for three-ring and four-ring cylindrical roller bearings. Otherwise, due to the increase in lubrication and stirring, the temperature of the bearing must be much higher in the hundreds of hours of operation of the high-speed offset printing press. Therefore, the amount of grease during initial lubrication and relubrication must be carefully determined according to the type of bearing. We recommend consulting the engineering service department of the Schaeffler Group. Friction and temperature rise In order to determine the friction value in friction calculation, the speed and load must be known. In addition, the type of lubrication, the method of lubrication and the viscosity of the lubricant at the working temperature are also necessary factors for the calculation. The friction and friction energy of printing press bearings with working clearance can be calculated approximately. Total friction torque MR: friction power NR: friction torque related to speed · n 2 000: friction torque related to speed · n 2 000: for cylindrical roller bearings and double-row tapered roller bearings, and load Relevant friction torque (in the printing machine, tapered roller bearings mainly bear radial load): MR Nmm Total friction torque M0 Nmm Friction torque related to speed M1 Nmm Friction torque related to load NR W Friction power n min1 Working speed f0 For the bearing coefficients used in the calculation of the friction torque related to the 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 the operating temperature dM mm Average bearing diameter (d + D)/2f1 Bearing coefficient used for the calculation of load-related friction torque, see page 21, table FN for radial bearings In order to bear the radial load, for the thrust bearing, it is the axial load. Bearing factors The 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 only valid for bearings after running-in and evenly distributed lubricant. For newly filled grease, the bearing factor f0 should be increased to 2 to 5 times. For oil bath lubrication, the oil height 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 factor of cylindrical roller bearing with cage Bearing factor of thrust roller bearing Bearing factor of tapered roller bearing Bearing factor of preloaded printing press bearing Preloaded bearing, the rolling elements bear additional load. Depending on the degree of preload, the friction torque may increase.