Ultra precision angular contact ball bearings are mainly used in machine tool spindles, textile machinery, woodworking machinery and parts with high requirements for reliability, operation accuracy and high speed. The ultra precision angular contact ball bearing used for the main shaft represents the reliability of use. Ultra precision bearings refer to bearings whose precision level reaches P4 or ultra precision
Products with P4 grade accuracy. Such as P4, P4S, P4S - K5 and P2 grades.
Ultra precision angular contact ball bearing should not only guide the high-precision operation of mechanical parts, but also ensure sufficient support in the process of high-speed operation. In order to fully meet the working requirements, the bearing must run without wear.
1. Service life of ultra precision angular contact ball bearing
Ultra precision angular contact ball bearing should not only guide the high-precision operation of mechanical parts, but also ensure sufficient support during high-speed operation. Therefore, the selection of bearing should mainly consider the main factors of precision, rigidity and operation performance. When bearing, it must be ensured that there is lubricating oil film in the contact area between the rolling element and the raceway. Under the condition of oil film, the actual fatigue life of the bearing will be longer. If the bearing wants to achieve fatigue life, the life of the bearing is deeply affected by the life of the lubricant. Under the relevant load conditions, the factors that determine the working life of the bearing are the contact stress in the contact area between the rolling element and the raceway and the dynamic performance of the bearing. In the actual working process, the failure of ultra precision bearing will not be caused by fatigue, but the failure caused by the loss of service life of lubricating grease.
The fatigue life of ultra tight angular contact ball bearings generally depends on the working life of the lubricant. In many cases, the life of the lubricant determines the life of the bearing. The relative influence of bearing fatigue life is small.
2. Fatigue load: in order to check the fatigue load, the load ratio so is calculated according to the following formula
So=Co/Po
Tel t so: fatigue load ratio (dynamic load safety factor)
Co: basic rated static load n
Po: equivalent static load, which can be calculated by equivalent static load formula, but dynamic load is used in calculation. The equivalent static load Po is calculated from the axial and radial loads of the bearing. The stress caused by this force at the center of the maximum stress area between the rolling element and the contact surface of the raceway is equal to the stress caused by the synthesis of the actual load. For the bearing with the largest actual load, its bearing capacity shall be tested. If the dynamic load ratio so > 8 is the main prerequisite to meet the fatigue load, the more accurate method is to measure the contact stress of the bearing alone, or use special calculation software to detect the dynamic performance of the bearing
If the effective lubricating oil film (viscosity ratio K ≥ 2) and extremely high cleanliness and other conditions can
If the requirements are met, there is no need to calculate the rated life of the bearing. If these preconditions cannot be met, the influence of lubrication and cleanliness on the bearing can be calculated manually by the modified life calculation company is0281 or by the computer-aided calculation in Appendix 4 of din281.
3. Cleanliness
For ultra precision bearings, the cleanliness of the contact surface between the rolling element and the raceway has a great impact on the service life of the bearing, because pollutants will sharply increase wear and reduce the service life of the bearing. The guiding value of oil lubrication cleanliness is derived from oil pressure conditions. For grease lubrication, if the bearing is equipped with initial grease and sealed, the bearing has the highest cleanliness grade.
4. Operating temperature
For ultra precision bearings, the ring material can ensure that the dimension temperature is + 150 ° C. if it is higher than this temperature, the influence of temperature on the performance of bearing materials needs to be considered. However, pay attention to the limit temperature of each component, such as the temperature of cage (+ 100 "C), bearing seal (+ 100 ° C) and lubricant.