Some experiences of the hottest hydrostatic import

2022-09-30
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Some experience of hydrostatic imported bearing in maintenance

hydrostatic imported bearing has high rotation accuracy, good rigidity, high bearing capacity, no wear and high durability. The following are some experience gained from the exploration and attempt of hydrostatic imported bearings in the maintenance process, which are for your reference only

1. Orifice restrictor: br

(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. Throttle ratio β The theoretical value of is 1.2 ~ 1.5, and according to years of experience, 1.25 is better. Thus, in the maintenance, the geometric accuracy of the main shaft, the geometric accuracy of the front and rear bearing shells, coaxiality, roundness and taper should be strictly controlled according to the above conditions, so as to ensure β Value. Determine the E value (the eccentricity of the geometric center of the spindle and bearing bush) according to the bearing capacity of the machine tool, so that β Value is the best

(3) when the main shaft is not installed in each oil chamber, the oil column at each oil outlet must be consistent (observation method). If it is inconsistent, futures should be adopted: the afternoon oscillation of coke 1701 contract is too strong, and the method of changing the orifice diameter of the restrictor 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 various new materials continue to appear. The hole diameter is 0.25 ~ 0.4mm

2. Thin film feedback restrictor

the rigidity of thin film feedback throttle bearing is very large, but the machine tool also often has the phenomena of bearing pad holding, galling, pressure drop and so on in operation. 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 into a 4mm thick rigid film, pad the lower cavity with 0.05mm thick tin foil paper, and adjust the spindle to a position 0.05mm higher than the ideal position. 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 imported bearings, except that the universal insurance of coarse filtration and fine filtration has actually indirectly realized marketization, other components have a protective effect on hydrostatic bearings. 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:

wear resistant electrode

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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