Installation process guidance for super precision bearings
The manufacturing process of super-precision bearings maintains an extremely high standard of clean environment, very strict inspections, and uses high-quality packaging for protection. In order not to affect the high performance of the bearing, care must be taken during the installation process. It is best to have a separate and clean installation room. Preparation of components Only approved components can be used for installation. Depending on the part, the approval procedure includes dimensional inspection, optical inspection or pre-balance process. The matching installation of components has a decisive influence on the function of the bearing. Therefore, it is sometimes necessary to match the bearing with the main shaft or bearing seat. For spindle bearings, the bore diameter and outer diameter tolerances are divided into several groups, where the average tolerance of each group is marked on the packaging and the bearing. The actual deviation of the bearing width is also marked on the bearing (see page 19). Matching procedure In order to obtain the best performance or realize the precise positioning of the spindle relative to the bearing seat, some special adjustments must be made, such as the end cover for the axial clamping of the bearing outer ring in the bearing seat, and the bearing seat before tightening There is a gap on the end face (as shown in Figure 2). For high-speed spindles, spacer rings are recommended to compensate for the effect of installation and preloading on the expansion of the ferrule. Grease ultra-precision bearings do not need to be cleaned before grease is added. Please see Table 4 on page 179 for the filling amount of grease. Grease filling must be carried out under extremely clean conditions. The filling amount of grease requires high requirements for filling and measuring equipment. Therefore, it is recommended to choose a sealed bearing filled with grease by Schaeffler. Installation: When installing the bearing on the shaft or bearing seat, the rolling elements cannot bear the load. Before installation, parts with tight fit (interference fit) must be heated. If the induction heating equipment in Figure 3 is used, the heating process will be simple, fast and clean. Table 4 and Table 5 show the clamping force for locking the inner ring of the bearing by the lock nut. In order to avoid improper installation, the nut can be tightened at 3 times the given torque, then loosened, and finally tightened with the given torque. Installation guide The installation and operation test and grease distribution of super-precision bearings. For grease-lubricated bearings, the grease running-in operation must be carried out before the spindle operation test. Please refer to the appendix (page 230) for the filling amount of grease and the guidance of the grease running-in process. Lock nut recommendations: The lock nut is often used to clamp the inner ring of the spindle bearing and fix it on the shaft. A lock nut with an axial hole to fix the bearing on the shaft is better than a lock nut with a radial groove because it has the least air turbulence during high-speed rotation. The mounting surface of the lock nut must be ground on the same fixture as the thread. The axial runout value is recommended to be less than 2μm. The gasket of the clamp should be ground together with the thread and end face of the lock nut to prevent deflection during the clamping process. In order to ensure the quality of the spindle bearing installation, it is recommended to record the following measured values: journal diameter, interference, spacer size difference, steady-state temperature, radial and axial runout values.