Because the spindle is a high-speed precision components, regular maintenance is very necessary. Regular maintenance of the spindle is as follows:
1. The axial runout of the spindle is generally required to be 0.002mm (2μm), and it is tested twice a year.
2, the radial runout of the tapered hole in the motor spindle is generally required to be 0.002mm (2μm), and is tested twice a year.
3. The radial runout of the distal end (250mm) of the mandrel of the spindle is generally required to be 0.012mm (12μm), and it is tested twice a year.
4, butterfly spring tightening force requirements for: 16 ~ 27KN (HSK63 as an example) 2 times a year test.
5. The distance of pulling tool lever extending when loosening the tool is 10.5±0.1mm (HSK63 for example) 4 times a year.
Analysis of serious heat generation when the spindle rotates at high speed and the treatment process:
The problem of heat generation and temperature rise in the operation of the electric spindle is always the focus of research. There are two main heat sources inside the electric spindle unit: one is the spindle bearing and the other is the built-in main motor.
The most prominent problem of the spindle unit is the heat generation of the built-in main motor. Since the main motor is next to the spindle bearing, if the main motor heat dissipation problem is not solved, it will also affect the reliability of the machine tool. The main solution is the use of circulating cooling structure, divided into two kinds of external and internal circulation, the cooling medium can be water or oil, so that the motor and the front and rear bearings can be fully cooled.
The spindle bearing is the core support of the spindle, but also one of the main heat sources of the spindle. The current high-speed spindle, most of the use of angular contact ceramic ball bearings. Because ceramic ball bearings have the following characteristics:
①As the ball weight is light, the centrifugal force is small, the dynamic friction torque is small.
②The thermal expansion caused by temperature rise is small, so that the bearing preload stability.
③Small elastic deformation, high stiffness, long life. Due to the high running speed of the electric spindle, there are strict requirements on the dynamic and thermal state performance of the spindle bearing. Reasonable preload, good and sufficient lubrication is necessary to ensure the normal operation of the spindle.
Oil mist lubrication is adopted, the inlet air pressure of atomization generator is 0.25~0.3MPa, 20# turbine oil is selected, and the oil droplet speed is controlled at 80~100 drops/min. The lubricant mist fully lubricates the bearings while taking away a large amount of heat. The lubricant distribution of the front and rear bearings is a very important issue and must be strictly controlled. The air inlet cross-section is larger than the sum of the cross-section of the front and rear oil injection ports, the exhaust should be smooth, the spray angle of the oil injection holes and the axis of the 15o angle, so that the oil mist is sprayed directly into the working area of the bearings.
The main points of the spindle repair process:
1, according to the damage of the spindle, measure the static and dynamic radial runout and lifting clearance and axial runout.
2, with homemade special tools to disassemble the electric spindle. Clean and measure the rotor swing and wear.
3, optional bearings. The consistency error of the bore and outer diameter of each group of bearings should be ≤0.002~0.003mm, and the bore of the sleeve to maintain a clearance of 0.004~0.008mm; with the spindle to maintain a clearance of 0.0025~0.005mm. In practice, it is best to use both thumbs to push the bearing into the sleeve fit. Too tight will cause deformation of the outer ring of the bearing, bearing temperature rise is too high, too loose will reduce the rigidity of the grinding head.
4, bearing cleaning, is to ensure that the normal operation of the bearing and the service life of the important links, do not use compressed air to blow around the bearing, because of the hard particles in the compressed air will make the raceway pull hair.
5, tapered bearings or angular contact ball bearings must pay attention to the direction of bearing mounting, otherwise it can not reach the rotary accuracy requirements. The whole assembly process using special tools, in order to eliminate assembly errors, to ensure the quality of assembly.
6, when the sleeve bore deformation, roundness is too poor, or too loose with the bearing, can be used to compensate for the local plating method and then grinding to the requirements, the journal can also use this method.
7, the spindle on the round nut, oil seal cover and other parts of the end face respectively with the bearing inside and outside the ring of the end of the close contact, and therefore the threaded part of its perpendicularity to the end of the surface of the requirements of high, you can use the color method to check the contact situation. If the contact rate 8, assembled spindle for axial adjustment (adjusted with a tension scale measurement), at the same time should measure the static and dynamic radial runout and lifting clearance, until it reaches the assembly process requirements.
9, in the actual operating conditions of the machine, excluding the assembly, machine operation of thermal deformation and other factors, at a certain speed, the application of dynamic balancing instrument for dynamic balancing of the rotor.
Maintenance analysis and elimination of common problems of electric spindle:
1, spindle heat
(1) spindle bearing preload is too large, resulting in excessive friction when the spindle rotates, causing the spindle temperature to rise sharply.
Troubleshooting method: can be excluded by readjusting the spindle bearing preload.
(2) the spindle bearing research injury or damage, will also cause the spindle rotary friction is too large, causing the spindle temperature rises sharply.
Troubleshooting method: can be eliminated by replacing the new bearing.
(3) spindle lubricating oil is dirty or impurities, will also cause the spindle rotary resistance is too large, causing the spindle temperature increases.
Troubleshooting method: by cleaning the spindle box, re-oil to be excluded.
(4) spindle bearing lubricating grease depletion or too much lubricating grease, will also cause the spindle rotary resistance, friction is too large, resulting in spindle temperature rise.
Troubleshooting method: by reapplying grease to eliminate.
2, the spindle stops when cutting
(1) the spindle motor and the spindle connected to the drive belt is too loose, resulting in the spindle drive torque is too small, strong cutting spindle torque is insufficient to produce alarms, CNC machine tools automatically stop.
Troubleshooting method: by re-adjusting the tension of the spindle drive belt, to be eliminated.
(2) the spindle motor and the spindle connected to the transmission belt surface oil, resulting in spindle transmission belt slippage, strong cutting spindle torque is insufficient to produce alarms, CNC machine tools automatically stop.
Troubleshooting method: by using gasoline or alcohol to clean and wipe clean to be excluded.
(3) spindle motor and spindle connected to the drive belt used for too long and failed, resulting in the spindle motor torque can not drive, strong cutting spindle torque is insufficient to produce alarms, CNC machine tools automatically stop.
Troubleshooting method: by replacing the new spindle drive belt to be eliminated.
(4) spindle drive mechanism in the clutch, coupling connection, adjustment, too loose or wear, resulting in the spindle motor torque transmission error is too large, strong cutting spindle vibration. Generate an alarm, the CNC machine tool stops automatically.
Troubleshooting method: by adjusting, replacing the clutch or coupling to be excluded.
3, spindle work noise
(1) spindle components dynamic balance is poor, so that the spindle rotary vibration is too large, causing noise.
Troubleshooting method: need to machine tool manufacturers of professionals on all the spindle components to re-carry out dynamic balance check and debugging.
(2) spindle drive gear wear, so that the gear mesh clearance is too large, the spindle rotary impact vibration is too large, causing noise.
Troubleshooting method: need to machine tool manufacturers of professional personnel on the spindle drive gear inspection, repair or replacement.
(3) spindle bearing hair or damage, so that the spindle rotary clearance is too large, rotary shock, vibration is too large, causing noise.
Troubleshooting method: need to machine tool manufacturers of professional personnel to check, repair or replace the bearing.
(4) spindle drive belt slack or wear, so that the spindle rotary friction is too large, causing noise.
Troubleshooting method: by adjusting or replacing the drive belt to be eliminated.
4, the tool can not be clamped
(1) disc spring displacement is too small, so that the spindle to grab the knife, the clamping device can not reach the correct position, the tool can not be clamped.
Troubleshooting method: by adjusting the length of the disc spring travel to be eliminated.
(2) spring collet damage, so that the spindle clamping device can not clamp the tool.
Troubleshooting method: by replacing the new collet to eliminate.
(3) disc spring failure, so that the spindle to grab the knife, the clamping device can not move to the correct position, the tool can not be clamped.
Troubleshooting method: by replacing the new disc spring to be eliminated.
(4) shank spigot is too long, the top hit the spindle knife, clamping device, so that it can not move to the correct position, the tool can not be clamped.
Troubleshooting method: by adjusting or replacing the spigot, and correctly installed to eliminate.
5, the tool can not be loosened after clamping
(1) loosen the knife hydraulic cylinder pressure and stroke is not enough.
Troubleshooting method: by adjusting the position of the hydraulic pressure and travel switch to eliminate.
(2) disc spring compression is too tight, so that the spindle clamping device can not fully move to the correct position, the tool can not be released.
Troubleshooting method: by adjusting the disc spring on the nut, reduce the amount of spring compression to be eliminated.
The electric spindle has a compact structure, light weight, small inertia, low vibration, low noise, fast response, etc., can reduce the gear drive, simplify the shape of the machine design, easy to realize the spindle positioning, is a high-speed spindle unit in an ideal structure. As the most critical component of high-speed CNC machine tools, its performance largely determines the machining accuracy and productivity of the entire high-speed machine tool, electric spindle as the core component of the machining center, it will be the machine tool spindle and AC servo motor shaft into one, that is, the stator and rotor of the spindle motor is directly mounted into the spindle assembly inside, and after accurate dynamic balancing corrections, it has good rotary accuracy and stability, forming a perfect high-speed spindle unit, and it is an ideal structure for high-speed spindle unit. Stability, the formation of a perfect high-speed spindle unit, also known as internal electric spindle, which no longer use the belt and gear drive vice, thus realizing the machine tool spindle system "zero transmission", power on the rotor directly drive the spindle operation.