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Experience sharing on hydrostatic NSK Bearings

Hydrostatic bearings has high rotation accuracy, good rigidity, high bearing capacity, no wear and high durability.

Orifice restrictor of hydrostatic Bearings

  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 the 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, 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 β Value hydrostatic Bearings. 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.
  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.
hydrostatic NSK Bearings
hydrostatic NSK Bearings
hydrostatic Bearings

Membrane feedback restrictor of hydrostatic Bearings

  1. The stiffness of the thin film feedback throttle hydrostatic NSK Bearings is very large, but the phenomena of pad holding, roughening and pressure drop often occur in the operation of machine tools. 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 hydrostatic NSK Bearings parameters.

  2. 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) hydrostatic NSK Bearings.

Improvement of oil supply of hydrostatic Bearings

In the oil supply system of hydrostatic NSK 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 magnitude of cavity pressure and hydrostatic NSK Bearings 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 NSK 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. There is a gap of 0.04 ~ 0.05mm between the main shaft and bearing bush of static pressure NSK bearing, and the oil in between has a certain resistance value. By detecting the change of this resistance value, we can know the size of the interval 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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