Maintenance method of static pressure inlet bearin

2022-08-14
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Maintenance method of static pressure imported bearing of grinding machine in imported bearing

static pressure imported bearing has high rotation accuracy, good rigidity, high bearing capacity, no wear and high durability. The following is the operation process of the hydrostatic inlet shaft hydraulic pressure testing machine, which is based on the experience gained during the exploration and attempt in the maintenance process, for your reference only

1. Orifice restrictor:

(1) Change internal throttling to external throttling, and install a pressure gauge to instantly display the pressure of the upper and lower chambers

it makes maintenance convenient, especially it can be easily cleaned regularly, which is unmatched by the internal throttle

(2). Throttle ratio. The theoretical value of throttling ratio is between 1.2 and 1.5, and 1.25 is better according to years of experience. Thus, during maintenance, it is necessary to strictly control the geometric accuracy of the main shaft, the geometric accuracy of the front and rear bearing shells, coaxiality, roundness and taper, so as to ensure the value. According to the bearing capacity of the machine tool, determine the E value (the eccentricity of the geometric center of the main shaft and bearing bush) to make the value the best

(3). When the main shaft is not installed in each oil chamber, the oil column of each oil outlet must be consistent (observation method). If it is inconsistent, the method of changing the orifice diameter of the throttle should be adopted to change its flow. Take 4 cavities as an example. Generally, the oil column of the lower, left and right cavities is between 20 ~ 25mm, and the diameter of the small hole is 0.25 ~ 0.4mm

2. Film feedback throttler:

the stiffness of film feedback throttling bearing is very large, but the machine tool also often has the phenomena of pad holding, galling, pressure drop and so on. The key of film feedback is film. In practice, it is believed that the main reasons for bearing bush locking and galling are: ① plastic deformation of film; ② Feedback is slow. When the external load changes abruptly and the film has not reacted, the shaft and the pad have rubbed; ③ Film fatigue. The film has long service time and fatigue deformation, which is equivalent to changing the feedback parameters

good results can be achieved by increasing the thickness of the film and using some fatigue resistant materials. Generally, rigid membrane, preloading and reserved gap are used. The specific method is: change the 1.4mm thick film measuring the height of electrolyte in each shift to 4mm thick rigid film, and pad 0.05mm thick tin foil paper in the lower cavity, so that the spindle is adjusted to a position 0.05m higher than the ideal position, which is safe, environmentally friendly and lightweight, and cannot be neglected for 1m. The purpose is to return to the ideal center just after the spindle is stressed (grinding wheel weight, cutting force)

3. Improvement of oil supply system:

in the oil supply system of hydrostatic inlet bearing, except for coarse filtration and fine filtration, other components have a protective effect on hydrostatic bearing. The oil supply system is improved on the basis of the original system

(1). The oil outlet behind the throttle plate is connected with a pressure relay and a pressure gauge (originally in front of the accumulator), so that the operator can see the chamber pressure and inlet pressure. When the differential pressure is greater than a certain value, the machine can be shut down immediately to prevent the bearing bush from locking. For example, the inlet pressure is 2MPa, and the outlet cavity pressure is 1.2 ~ 1.6Mpa. If it is lower than 1.2MPa, the machine will be shut down

(2). Add a digital detection device:

there is a gap of 0.04 ~ 0.05mm between the main shaft and the bearing bush of the hydrostatic inlet bearing, and the oil in the gap has a certain resistance value. Detect the change of this resistance value, and you can know the size of the gap. Take the main shaft as one pole and the bearing bush as the other pole, and measure the resistance change. After processing, the signal is sent to the photoelectric alarm and the control system amplifier to control the start and stop of the spindle motor, so as to avoid the friction between the shaft and the bearing

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