What are the improvements of self-lubricating bearings?
For imported self-lubricating bearings, the quality will be more guaranteed. Today, let’s talk about the improvements of imported self-lubricating bearings. Let’s take a look.
Imported self-lubricating bearings have high rotation accuracy, good rigidity, high bearing capacity, no wear and high durability.
1. Improvement of oil supply system:
In the static pressure imported self-lubricating bearing oil supply system, in addition to the coarse filter and the fine filter, the other components have a protective effect on the static pressure bearing. Improve the oil supply system on the basis of the original system.
(1). 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 imported self-lubricating bearing, and the oil in between has a certain resistance value. By detecting the change of this resistance value, the size of the expected gap can be known. Take the main shaft as one pole and the bearing bush as the other pole, and measure the resistance change. This signal is processed and sent to the photoelectric alarm and the control system amplifier to control the start and stop of the spindle motor to avoid friction between the shaft and the bush.
(2). Connect a pressure relay and a pressure gauge (originally in front of the accumulator) at the oil outlet behind the throttle plate, so that the operator can see the size of the cavity pressure and the inlet pressure. When the pressure difference is greater than a certain value, stop the machine immediately to prevent the bearing from locking up. For example, the inlet pressure is 2MPa, and the outlet pressure is 1.2~1.6MPa. If it is lower than 1.2MPa, the machine will be shut down.
2. Thin film feedback throttle:
The stiffness of the thin film feedback throttling bearing is very large, but the machine tool often exhibits such phenomena as shingling, fraying, and pressure drop during the operation. The key to the film feedback is the film. In practice, it is believed that the main reasons for the bearing shell blocking and roughening are: ① caused by the plastic deformation of the film; ② slow feedback. When the external load changes suddenly and the film has not reacted, the shaft and the bush have rubbed; ③The film is fatigued. The film has a long use time and fatigue deformation, which is equivalent to changing the feedback parameters.
Increasing the thickness of the film and changing to some fatigue-resistant materials can achieve good results. Generally, a rigid film, pre-loading, and gap-preserving method are used. The specific method is: change the 1.4mm thick film to a 4mm thick rigid film, and pad 0.05mm thick tin foil in the lower cavity to adjust the spindle to a position 0.05mm higher than the ideal position. The purpose is to return to the ideal center exactly when the spindle is stressed (wheel weight, cutting force).
3. Orifice restrictor:
(1). When each oil cavity is not equipped with a main shaft, the oil column of each oil outlet must be the same (observation method). If it is inconsistent, the method of changing the aperture of the throttle should be adopted to change the flow rate. Take 4 cavities as an example. Generally, the oil column in the lower, left and right cavities is between 20-25mm, and the diameter of the small hole is 0.25-0.4mm.
(2). Throttling ratio. The theoretical value of the self-lubricating bearing of the throttling ratio β is between 1.2 and 1.5, and 1.25 is better based on years of experience. In the maintenance of this copper sleeve, it is necessary to strictly control the geometric accuracy of the spindle, the geometric accuracy of the front and rear bearings, the coaxiality, the roundness and the taper in order to ensure the β value. Determine the e value (the eccentricity between the spindle and the geometric center of the bearing bush) according to the load capacity of the machine tool.
(3). Change the internal throttling to the external throttling, and add oil-free bearing pressure gauges to display the pressure of the upper and lower chambers in real time. Makes maintenance convenient, especially it can be easily cleaned regularly, which is unmatched by the internal throttle.