With the development of numerical control technology, hydrostatic bearings are also widely used in the spindles of CNC machine tools such as machining centers. CNC gantry grinders have many hydrostatic grinders and hydrostatic diamond boring heads. Some explorations and attempts have been made in maintenance, and several Some experience.
- 1. Change the internal throttling to the external throttling, and install a pressure gauge to display the pressure of the upper and lower chambers immediately. 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 β is between 1.2 and 1.5, and 1.25 is better based on years of experience. In this way, in maintenance, it is necessary to strictly control the geometric accuracy of the spindle, the geometric accuracy of the front and rear bearings, the coaxiality, roundness and 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-bearing capacity of the machine tool to make the β value the best.
- 3. When the main shaft is not installed in each oil cavity, the oil column of each oil outlet must be consistent (observation method). If they are 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 holes is 0.25-0.4mm.
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 operation. The most critical part of the film feedback is the film. In practice, it is believed that the main reasons for the bearing shell blocking and roughening are:
- ① due to plastic deformation of the film;
- ②Slow feedback. When the external load changes suddenly and the film has not reacted, the shaft and the bush have rubbed;
- ③Film fatigue. The film has been used for a long time and deformed due to fatigue, which is equivalent to changing the feedback parameters.
Increasing the thickness of the film and using some fatigue-resistant materials can achieve good results. Generally, rigid film, pre-loading, and reserved gap method are used. The specific method is: change the 1.4mm thick film to a 4mm thick rigid film, pad 0.05mm thick tin foil in the lower cavity, and 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 (grinding wheel weight, cutting force).