The regular protection of the electric spindle

- May 11, 2020-

The regular protection of the electric spindle is as follows:

1. The axial runout of the electric spindle is generally required to be 0.002m m (2 μ m), which is tested twice a year.

2. The radial runout of the taper hole in the electric spindle is generally required to be 0.002m m (2 μ m), which is tested twice a year.

3. The general requirements for radial run out of the distal end (250m m) of the spindle mandrel are: 0.012mm (12 μ m), which is tested twice a year.

4. The tension requirement of butterfly tension spring is: 16 ~ 27kn (take hsk63 as an example) tested twice a year.

5. The extension interval of broach rod when loosening is 10.5 ± 0.1mm (take hsk63 as an example), and it is tested four times a year

Hot fault maintenance: fault phenomenon: the spindle motor is heated seriously when rotating at high speed

Analysis and treatment process: the heating and temperature rise in the operation of electric spindle is always the focus of discussion. There are two primary heat sources inside the motorized spindle unit: one is the spindle bearing, the other is the built-in main motor. The most prominent problem of the electric spindle unit is the heating of the internal main motor. Because the main motor is surrounded by the spindle bearing, if the heat dissipation of the main motor is not handled well, it will affect the reliability of the machine operation. The primary treatment method is to adopt circulation cooling structure, especially circulation and internal circulation. The cooling medium can be water or oil, so that the motor and front and rear bearings can be fully cooled.

The spindle bearing is the core support of the electric spindle, and also one of the primary heat sources of the electric spindle. At that time, most of the high-speed motorized spindles used angular touch ceramic ball bearings. Because the ceramic ball bearing has the following characteristics:

1. Because the ball weight is light, the centrifugal force is small, and the dynamic friction torque is small.

2. The small thermal expansion caused by temperature rise makes the preload of bearing stable.

3. Small elastic deformation, high rigidity and long service life. Because of the high working speed of the electric spindle, there are strict requirements for the dynamic and hot functions of the spindle bearing. Reasonable preload, excellent and abundant lubrication are the necessary conditions to ensure the normal operation of the spindle. Oil mist lubrication is adopted. The air pressure of atomizer is 0.25 ~ 0.3MPa. 20 × turbine oil is selected. The oil drop speed is controlled at 80 ~ 100 drops / min. The oil mist not only sufficiently lubricates the bearing, but also takes a lot of heat away. The distribution of lubricating oil between the front and rear bearings is a very important problem, so it is necessary to control it strictly. The air inlet section is larger than the sum of the front and rear nozzle sections, so the exhaust shall be smooth. The angle between the eruption angle of each injection hole and the axis is 15O, so that the oil mist can be directly injected into the bearing operation area.