NSK Bearings relevant experience sharing hydrostatic
NSK Bearings its high hydrostatic rotary precision, good rigidity, high capacity, no wear and durability. Here is the hydrostatic bearing NSK explore and try a few lessons learned during maintenance, for your reference.
An orifice restrictor:
(1) would be replaced by an external internal throttle throttle, and the installation of the upper and lower chamber pressure gauge real-time display. Makes maintenance easy, in particular, can be easily cleaned regularly, this is an internal restrictor unmatched.
(2). Throttle ratio. Throttle than the theoretical value β is between 1.2 to 1.5, according to years of experience, preferably 1.25. Such maintenance, the need for geometric precision spindle, front and rear bearing geometric accuracy, concentricity, roundness and taper strictly controlled in order to ensure β values. Determine the value of e (the eccentric amount of the geometric center of the spindle and bearing) according to the carrying capacity of the machine, so that β value best.
(3). The oil chamber when the spindle is not installed, the oil port of oil each column must be consistent (observation), if not, should be taken to change the restrictor aperture methods to alter the flow. Chamber 4, for example, generally, the left, the right chamber of the oil column between 20 ~ 25mm, hole diameter 0.25 ~ 0.4mm.
(2) Film feedback throttle:
Film feedback throttle bearing stiffness is great, but the machine in operation often appear to hold tiles, napping, and so the pressure off. The most critical feedback film is a film, in practice considered, bearing locking, napping is mainly due to: ① caused by plastic deformation of the film; ② feedback slow. When external load mutation, the film did not react, the shaft has been rubbed with tile; ③ film fatigue. Film using a long time, fatigue deformation, the equivalent of changing the feedback parameters.
Increasing the thickness of the film and the use of some materials resistant to fatigue, may receive good results. Usually the film is rigid, pre-load, reserve gap method. Specific practice: the 1.4mm thick rigid 4mm thick film to film, the inferior vena pad 0.05mm thick aluminum foil, so that the spindle is adjusted to the desired position higher than the position of 0.05mm. The purpose is to force when the spindle (wheel weight, cutting force), the just return to the ideal center.
(3) supply system improvements:
NSK hydrostatic bearing oil supply system, in addition to the coarse filter, fine filter, the rest of the components have a protective effect on the hydrostatic bearing. In the original system, based on improvements on the fuel system.
(1). Connected pressure switch and pressure gauge after the throttle plate in the oil port (the original in the accumulator front), so that the operator can see the size of the cavity pressure and NSK pressure. When the pressure is greater than a certain value, in order to immediately shut down, in order to avoid bearing locking. Such as: NSK pressure 2MPa, export chamber pressure 1.2 ~ 1.6MPa, 1.2MPa going down below.
(2) increase the number detecting means:
NSK bearing between the spindle and hydrostatic bearing clearance 0.04 ~ 0.05mm, during which the oil has a certain resistance, this resistance change is detected, you can know the size of the gap. To the spindle pole, bearing another pole, measure the resistance changes. Send this post to a photoelectric alarm signal processing and control system amplifier, start and stop the spindle motor control, in order to avoid friction shaft and tile.
