NSK bearing selection must consider three main factors is the speed limit, the requirements of the service life and the predetermined bear the work load, which is the three requirements for performance of the selected NSK bearing must satisfy.
The speed limit is the maximum allowable working speed of NSK bearing, beyond this limit, the operating temperature of bearing lubricant will continue to rise, dry, so that the bearing is clamped, the speed limit so the selected NSK bearings NSK bearings taken than a predetermined maximum operating speed is 10% higher for suitable. In the bearing type has not been selected cases desirable predetermined installing NSK bearing parts, shaft and hole diameter and half for NSK bearing calculation of the average diameter of DM, the DM is multiplied by NSK bearing a predetermined maximum operating speed n, 10 / 9 times the DMN value should not be higher than the speed limit of the selected NSK bearing.
But the NSK bearing limit speed is not static, but directly related to lubrication. For example, take the bearings listed in NSK bearing limit speed under oil lubrication condition is N0, the same NSK bearing grease lubrication conditions in its speed limit is 0.8n0, in the oil mist lubrication conditions is 11.5n0; in a constant volume of non repeat circulating oil lubrication condition, continuous work for small oil tank for 0.85n0, and for intermittent working condition for large oil tank 0.95n0. Lubricating ways quite and N0 values is to repeat the cycle oil lubrication with filtering and heat radiating device, pay attention not to take this lubrication or the same effect as the other lubricating way, cannot take the N0 bearing sample values as the actual NSK bearing limit speed, and should be based on the specific way of lubrication, according to the above example will N0 multiplied by the constant a proportion, is taken as the actual NSK bearing limit speed value; secondly, the actual speed limit of NSK bearing although by improving lubrication and improved, but to consider for improving lubrication and pay the equipment cost and maintenance cost, space and other factors on the total and lubrication equipment, integrated balance gain and loss, make the best choice.
In fact, in considering the speed limit of NSK bearing, not only to take into account the type NSK bearing, sometimes also must consider the bearing components, such as retaining frame material, form printing design and technological factors, but also with the NSK inside the bearing sliding friction, and maintain a lubricant storage, is closely related to the stability of the rolling body operation, sometimes become requirements of life requirements on NSK bearing key bearing can achieve the limit speed and reliability are the unified consideration, usually take a reliability coefficient of 90%, which means that in the NSK bearing large numbers in the same working conditions in operation, NSK bearings 90% to still maintain the normal state in the working life of the L10 is scheduled to arrive at the when. If you want to get higher reliability, say 96%, we must reduce the requirements of the NSK bearing life, for example, the L10 must be life reduced to L4.
Speaking for the spindle bearing, the highest requirements are the same or slightly higher service life and the whole machine, the minimum requirement is to overhaul period longer than the lifetime of the spindle components, in fact, use both the host can meet the performance requirements without causing a comprehensive consideration of spindle system is too large and the economy is more cost-effective the scheme, for most machines, are quite successful precedent for reference.
It should be stressed, the selection and calculation of also should consider the failure form of NSK bearing, and wear, lubrication failure and fretting wear, which is to check the wear life, other forms of failure if the involved must also be considered.
Note that the fatigue life of NSK bearings can be expected and wear life not only with lubrication, but also directly related with the degree of the three clean lubricant for the installation location, bearing NSK bearing, NSK bearing itself, but also related with the form and effect of the seal, the selected NSK bearing rating life must adapt and provide lubrication, cleaning degree and the sealing condition, and improve these conditions can also improve the actual life of bearing NSK.
Considering the load factors should pay attention to the life of the bearing is more sensitive to load matching speed, so for the multi-stage transmission shaft, if possible, should be placed in the great series of deceleration later; for the main shaft bearing, if possible, the appropriate allocation between external load bearing pivot point and the NSK distance, and strive to reduce the spindle bearings NSK load, and strive to NSK main bearing load is stable, to avoid the impact and vibration, which requires the shape and position accuracy of the installation position of the bearing high enough clearance of NSK bearing and cooperate with the correct choice, installation precision bearing NSK good.
NSK selected in the selection of bearing load calculation in the design of the actual load situation, more can represent bearing work, calculated results is more correct, so to widely and deeply research on NSK bearing the actual load conditions.
If the NSK bearings can bear large load, and still and does not rotate, this state is more negative, the rolling body and micro indentation will be formed between the raceway and soon become pitting, so that the early failure of bearing. In this case, the static load must check the selected NSK bearing rating, can overcome the NSK bearing equivalent static load.
Another extreme case is just the opposite, NSK bearings operating at high speed, but does not bear the load, so that the rolling body raceway often in sliding without rolling, resulting in NSK bearing temperature rise rapidly, the lubricant is decomposed metamorphic, NSK bearings will be faster failure, so the NSK bearings require a minimum load to prevent slipping.
In some cases, must also consider the equipment itself produced by the axial force and radial force, gear and other parts of the weight even the weight of the shaft, the relevant components