Analysis Of The Causes Of Damage And Failure Of SKF Angular Contact Ball Bearings During Use
08/11/2023Cylindrical Roller Bearings: Essential Components for Industrial Equipment
10/11/2023
- Small hole restrictor:
(1) Change the internal throttling to external throttling, and install a pressure gauge to instantly display the upper and lower chamber pressures. It makes maintenance convenient, especially it can be easily cleaned regularly, which is unmatched by internal flow restrictors.
(2) Throttle ratio. The theoretical value of the throttling ratio β is between 1.2 and 1.5, and according to many years of experience, 1.25 is optimal. In this way, during maintenance, it is necessary to strictly control the geometric accuracy of the spindle, the geometric accuracy of the front and rear bearing bushes, coaxiality, roundness and taper to ensure the β value. Determine the e value (the eccentricity of the geometric center of the spindle and the bearing bush) according to the load-bearing capacity of the machine tool to optimize the β value.
(3) When the main shaft is not installed in each oil chamber, the oil columns of each oil outlet must be consistent (observation method). If they are inconsistent, the method of changing the aperture of the throttle should be used to change its flow rate. Taking a 4-cavity model as an example, generally the oil columns in the lower, left, and right chambers are between 20 and 25 mm, and the diameter of the small holes is 0.25 and 0.4 mm.
2.Thin film feedback throttle:
The stiffness of the film feedback throttling NTN bearing is very high, but the machine tool often suffers from tile-holding, fuzzing, pressure loss, etc. during operation. The most critical factor in film feedback is the film. In practice, it is believed that the main reasons for bearing locking and linting are: 1. Plastic deformation of the film; 2. Slow feedback. When the external load suddenly changes, the shaft and the pads are already rubbing before the film reacts; ③ Film fatigue. When the film is used for a long time, fatigue deformation is equivalent to changing the feedback parameters.
Increasing the thickness of the film and switching to some fatigue-resistant materials can achieve good results. Generally, the method of rigid membrane, pre-loading and reserved gaps is used. The specific method is: change the 1.4mm thick film to a 4mm thick rigid film, place a 0.05mm thick tin foil paper in the lower cavity, and adjust the spindle to a position 0.05mm higher than the ideal position. The purpose is to return the spindle to the ideal center exactly after receiving force (grinding wheel weight, cutting force).
- Improvement of oil supply system:
In the hydrostatic NTN bearing oil supply system, except for the coarse filter and fine filter, the other components have a protective effect on the hydrostatic NTN bearing. Improve the oil supply system based on the original system.
(1) Connect the pressure relay and pressure gauge (originally in front of the accumulator) to the oil outlet behind the throttle plate, so that the operator can see the chamber pressure and pressure. When the pressure difference is greater than a certain value, the machine can be stopped immediately to prevent the bearing from locking. For example: the pressure is 2MPa, the outlet pressure is 1.2~1.6MPa, if it is lower than 1.2MPa, the machine will be shut down.
(2) Add digital detection device:
There is a gap of 0.04~0.05mm between the main shaft and the bearing bush of the static pressure NTN bearing. The oil in the gap has a certain resistance value. By detecting the change in this resistance value, the size of the gap can be known. Take the main shaft as one pole and the bearing bush as the other pole, and measure the change in resistance. This signal is processed and sent to the photoelectric alarm and control system amplifier to control the start and stop of the spindle motor to avoid friction between the shaft and the tile.
