We know that most bearings are generally replaced after being damaged, but for some NSK bearings, if the cost is not high, we will choose to repair the bearings.
Reference transformation combined repair method
Sometimes the deformation of the design basis is too large to be used, so some other faces must be selected as the basis, and the dimensional chain is re-integrated. For example, if the deformation of the NSK bearing body is too large, the bearing body should be reprocessed and corrected based on the revolving component, and then the size of the reworked bearing body can be adjusted to adjust the assembly dimensional chain. The order of the arrangement is checked and repaired, and finally the purpose of controlling the accuracy of the closed loop is achieved.
Benchmark unchanged combination repair method
When repairing and adjusting the accuracy of the dimensional chain, according to the principle of reference coincidence, only one reference surface is used as the reference, that is, the design reference, and all other active surface repairs are based on this surface. This combination of repair benchmarks facilitates inspection accuracy and reduces accumulated errors. For example, when repairing a speed-controlled fluid coupling, the bearing body is often used as a reference.
1.Appropriate viscosity and good viscosity-temperature characteristics
In order to prevent the temperature of the spindle of the machine tool from becoming too high and cause thermal deformation of the machine tool, affect the machining accuracy or make the NSK bearing poorly lubricated, the appropriate temperature of the lubricating oil should be selected according to the structure of the spindle bearing, speed and bearing clearance, etc. Characteristics to prevent the lubricating performance from being affected by excessive changes in viscosity due to large changes in spindle operating temperature and ambient temperature.
In order to maintain a uniform oil film between the contact surface of the main shaft and the bearing, and the oil film will not be damaged when the main shaft starts or stops motion to produce an impact load, maintaining good lubrication performance plays a role in reducing friction and friction heat, reducing the temperature rise of the main shaft, and ensuring The role of machining accuracy requires good lubricating properties.
3.Good oxidation resistance
When the machine tool spindle adopts the circulation lubrication method, the spindle NSK bearing oil is required to be used for a long time without deterioration, so it is required to have good oxidation resistance.
4.Good rust resistance
Since oil products are inevitably mixed with condensed water or machine tool coolant in the air during the operation of the spindle lubrication system, the oil products are required to have good rust resistance.
Important role of preventing NSK bearing stripping and maintenance
The peeling damage of the NSK bearing means that when the bearing rotates under load, the raceway surface or rolling body surface of the inner and outer rings exhibits a scaly peeling phenomenon due to rolling fatigue.
The reasons for bearing peeling damage are
The bearing load is too large; the bearing is poorly lubricated or an inappropriate lubricant is used; poor installation, torque load, foreign body intrusion or water ingress; the bearing box is not accurate enough, the rigidity of the bearing box is uneven and the deflection of the shaft is large; rust and corrosion Points, scratches, and indentations.
Check the size of the NSK bearing load and the bearing used in the re-inspection; select the appropriate lubricant to lubricate the bearing and improve the lubrication method; improve the installation method, strictly follow the installation procedure for installation, improve the sealing device, and perform anti-rust measures during shutdown ; Check the accuracy of the shaft and bearing box, select a bearing with a high accuracy level; check the clearance of the bearing to make it appropriate.
Vibration of NSK bearings has a significant effect on bearing failure
For example: peeling, indentation, rust, cracks, wear, etc. will be reflected in the bearing vibration detection, so the size of the vibration can be measured by using a special bearing vibration measurement device (frequency analyzer and vibrometer, etc.). The frequency distribution can be inferred The details of the abnormal vibration are different. The measured values are different depending on the use premise of the bearing or the installation position of the sensor. Therefore, it is necessary to analyze and compare the measured values of each machine in advance to determine the judgment scale.
At present, the equipment using precision bearings is becoming more and more refined, and the grease used in NSK bearings must have the following functions:
(1) With the same operating life as the bearing, the maintenance cycle should be delayed as much as possible, the downtime should be shortened, and the labor productivity can be improved.
(2) At a high speed of dn>5×105, it is necessary to ensure that the temperature rise of the motor is low and oil is not dumped, thereby reducing power consumption and protecting the motor.
(3) The scalar content control is under the inevitable standard, and the pollution of the equipment noise to the situation is minimized.
(4) Under the premise of ultra-low temperature work, the flexibility of starting and running of the bearing is guaranteed, and the common problems of NSK bearings. Guaranteed minimum output power.
The cleaning of the removed NSK bearings is divided into rough cleaning and fine cleaning, and they are placed in the container, and the bottom of the metal mesh pad is placed first so that the bearing does not directly contact the dirt of the container. During rough cleaning, if the bearing is rotated with dirt, it will damage the rolling surface of the bearing, so care should be taken. In the crude cleaning oil, use a brush to remove smooth grease and adhesions. After roughly cleansing, transfer to fine washing.
How to effectively ensure the longest service life of NSK bearings
In order to ensure the long life of nsk bearings, which can not meet the general installation and adjustment requirements, it is important to take the following measures:
(1)The NSK bearings are grouped according to the size of their interference fit surfaces, and the bearings are arranged in order according to their clearance size in each group. Group the corresponding shaft or seat hole diameters in the same way. The bearing group with large interference fit surface size is matched with the shaft group or seat hole group with large diameter, and the corresponding group with small size and small diameter is matched. ERIC BEARING LTD are NSK bearings distributor , today share NSK bearing stock photo for reference :
In each matching group, NSK bearings with large clearances are tightly fitted, and NSK bearings with small clearances are loosely fitted. The result of this matching makes the NSK bearing's interference fit more consistent in the machines installed in the same batch, neither loose nor tight, and the clearance is more uniform, so as to ensure that the prestress after NSK bearing installation is appropriate. And avoid the occurrence of abnormal bearing failure such as creep, ring swell, shock, vibration or heat generated due to improper clearance, and engagement.
(2)The coaxiality of the journals and seat holes at both ends of the support and the perpendicularity to the support end surface must be strictly guaranteed to prevent the occurrence of additional loads. If possible, the mechanical components acting on the load other than the bearing should be slightly away from the NSK bearing that is more vulnerable to damage, and the shaft and rotating parts system should run as smoothly as possible.