Bearing damage is commonplace, but did you know that 80% of bearings fail early because they are not installed correctly? The correct installation of bearings can not only increase the service life of bearings, reduce costs, but also greatly improve production efficiency.
Bearing installation is very different from conventional parts and equipment. In order to achieve "tight thread seaming", you need to master specific methods and skills. It is not an exaggeration to describe "packing elephants into the refrigerator".
Before installation, it is necessary to confirm whether the bearing is kept intact, which is an important prerequisite for ensuring the installation of the bearing.
Bearing preservationBearing preservation has relatively harsh requirements on the environment
â— For storage environment such as warehouse, the temperature should be maintained at 0 ~ 40 degrees, and the humidity should be maintained below 60%
â— No large amount of dust and corrosive gas
The new bearings are packaged intact when they leave the factory and are equipped with anti-rust oil protection. Try to maintain the original packaging before preparing to use to avoid or reduce the occurrence of bearing product rust due to failure to take protective measures.
Bearing installationAfter ensuring that the properly preserved bearings are intact, you can proceed to formal installation.
The first step is to make adequate preparationsâ— Clean and tidy operation space
As a precision component, the bearing requires higher operating space during assembly. A clean and tidy space is beneficial to avoid early damage to the bearing caused by the introduction of impurities.
â— Prepare the parts and tools required in the installation process in advance
Prepare the necessary parts and tools during the entire installation process in advance, including screw nuts, thread glue, gaskets, heaters (or freezer), spreaders, torque wrenches, micrometers with inner and outer diameters, magnetic seats, dial indicators (or Sub-meter), feeler gauge, height gauge, spring scale, cleaning agent, cloth, dust-free paper, and other auxiliary devices.
â— Measure and record the size of key parts in advance
According to the general bearing design, the rotating parts are required to have an interference fit, and the stationary parts can be selected with a clearance fit. Compared with the thick shaft and bearing housing, the bearing is a relatively weak group and will be affected by the shape of the shaft or bearing housing. Before installation, it is necessary to measure and record the size of key parts in advance to avoid the impact of unqualified parts installation on bearings.
The second step is to choose the appropriate installation methodWe take the most common case where the inner ring rotation requires an interference fit on the shaft, and the outer ring is a clearance fit as an example to illustrate the bearing installation method.
For bearings with an interference fit, the inner ring is usually expanded by heating or the press is directly pressed in (only for small-sized bearings) and other methods.
â— Heating and expanding the inner ring
Bearing inner ring heating method: The bearing inner ring is usually heated by induction, heating furnace and oil bath. It is not allowed to use acetylene for heating, because its randomness is uncontrollable, which makes the bearing overheated or even scrapped.
Comparison of common heating methods:
Master the skills of heating temperature: the common industrial bearings stipulate that the maximum heating temperature does not exceed 120 degrees Celsius and the time does not exceed 8 hours; the maximum heating temperature of precision bearings does not exceed 66 degrees Celsius. In many cases, the bearing does not need to be heated to the highest temperature, you can use the following formula to calculate the amount of expansion ΔL generated by heating.
ΔL = α * ΔT * d
α: 11.7 * 10 -6 metal thermal expansion coefficient
ΔT: difference between heating temperature and ambient temperature (degrees Celsius)
d: bearing inner diameter (mm)
Although in theory, as long as the heating expansion is greater than the interference, the installation can be completed, but in fact the installation cannot be directly operated at this temperature. The temperature required for installation must be greater than this value. The time difference between heating and installation will cause a slight drop in temperature. In addition, the installation process can not be completely aligned, and the minimum clearance reserved for easy installation will also affect the installation, so the actual heating temperature selection needs to combine the calculation results of this formula with the above factors.
In the same way, if the outer ring needs to be frozen to install an application with an interference fit, the same formula is used and the same factors are considered, but the inner diameter value of the bearing is replaced by the outer diameter value of the outer ring.
â— Press in by pressThis method is only suitable for small size bearings.
First, the pressure needs to be in place. The required tonnage of the press can be calculated according to the formula. Secondly, choose the right tooling to match the press head and the bearing parts to be pressed. Generally, the sleeve-like parts are in contact with the bearing parts throughout the circumference. Finally, one of the most important steps is to apply pressure directly to the components that need to overcome the interference force. For example, if there is an interference condition in the inner ring, it is not possible to press the outer ring and use the raceways and rollers to transfer the force to the inner ring to achieve press fitting, which will cause damage to the bearing raceway.
The third step after installation inspection, double insuranceNo matter what kind of installation method is adopted, the inspection after installation can prevent the bearing from being pressed in place due to negligence of certain steps. For example, after heating and installation of large bearings, due to the effects of thermal expansion and contraction, a certain gap will be generated near the shaft shoulder when the temperature is lowered. This gap does not exist in the calculation and analysis. It is required to apply continuous clamping force during the cooling process to eliminate this gap. This is the typical scenario of correcting improper installation through post-installation inspection and correction.
For bearings installed by presses, if the radius of the shoulder is too large to exceed the radius of the bearing, the post-installation inspection becomes a correction such as inadequate press-in, machining errors, and pre-order missed inspection. The necessary procedures for other problems.
The above is a general overview of the bearing installation method. Due to the wide variety of bearings and the wide range of applications, the installation procedures and precautions also vary.
Ningbo Autrends International Trade Co.,Ltd. , https://www.mosvapor.com