What are the maintenance and elimination methods of electric spindle of boring machine?

Electric spindle is a new technology that combines spindle and spindle motor in the field of CNC machine tools in recent ten years. It is the "core" component of high-speed CNC machine tools, and its performance directly determines the high-speed machining performance of machine tools.

Because the motorized spindle is a high-speed precision component, regular maintenance is very necessary. Regular maintenance of motorized spindle is as follows:

1, the axial runout of motorized spindle is generally required to be 0.002mm(2μm), and it shall be tested twice a year.

2. The radial runout of the taper hole in the motorized spindle is generally required to be 0.002mm(2μm), and it shall be tested twice a year.

3. The general requirement for the radial runout of the distal end (250mm) of the motorized spindle is: 0.0 12mm( 12μm), and it is tested twice a year.

4. The tension requirement of butterfly spring is 16~27KN (taking HSK63 as an example), and it is tested twice a year.

5. When the broach lever is loosened, the extension distance is: 10.5 0. 1 mm (taking HSK63 as an example), and it is tested four times a year.

Analysis and treatment of serious heating when spindle rotates at high speed;

The problem of heating and temperature rise in the operation of motorized spindle has always been the focus of research. The motorized spindle unit mainly has two heat sources: one is the spindle bearing, and the other is the built-in main motor.

The most prominent problem of motorized spindle unit is that the built-in main motor generates heat. Because the spindle bearing is next to the main motor, if the heat dissipation problem of the main motor is not solved well, it will also affect the reliability of the machine tool. The main solution is to adopt circulating cooling structure, including external circulation and internal circulation, and the cooling medium can be water or oil, so that the motor and front and rear bearings can be fully cooled.

Spindle bearing is the core support of motorized spindle and one of the main heat sources of motorized spindle. At present, most high-speed motorized spindles adopt angular contact ceramic ball bearings. Because ceramic ball bearings have the following characteristics:

① Due to the light weight of the sphere, the centrifugal force is small and the dynamic friction moment is small.

② The thermal expansion caused by temperature rise is small, which makes the bearing preload stable.

③ Small elastic deformation, high rigidity and long service life. Due to the high speed of motorized spindle, there are strict requirements for the dynamic and thermal performance of spindle bearings. Reasonable pre-tightening force and good and sufficient lubrication are necessary conditions to ensure the normal operation of the spindle.

Oil mist lubrication is used, the inlet pressure of atomization generator is 0.25~0.3MPa, 20# turbine oil is selected, and the oil drop speed is controlled at 80~ 100 drops/minute. Lubricating oil mist can not only fully lubricate bearings, but also take away a lot of heat. Lubricating oil distribution of front and rear bearings is a very important issue, which must be strictly controlled. The cross section of the air inlet is greater than the sum of the cross sections of the front and rear oil injection ports, and the exhaust should be smooth. The injection angle of each injection hole forms an included angle of 15o with the axis, so that oil mist can be directly injected into the bearing working area.

Key points of maintenance technology for motorized spindle:

1. According to the damage of the motorized spindle, measure the static and dynamic radial runout, lift clearance and axial play.

2. Dismantle the motorized spindle with a self-made special tool. Clean and measure rotor runout and wear.

3. Match the bearing. The consistency error between the inner bore and the outer diameter of each group of bearings shall be ≤0.002~0.003mm, and a gap of 0.004~0.008mm shall be maintained with the inner bore of the sleeve; Keep a gap of 0.0025 ~ 0.005 mm from the spindle. In practice, it is best to push the bearing into the sleeve with two thumbs. Too tight will cause deformation of bearing outer ring, too high temperature rise of bearing, and too loose will reduce the stiffness of grinding head.

4. Bearing cleaning is an important link to ensure the normal operation and service life of the bearing. Do not blow the bearing with compressed air, because hard particles in the compressed air will make the raceway rough.

5, conical bearing or angular contact ball bearing must pay attention to the bearing installation direction, otherwise can not meet the requirements of rotary accuracy. Use special tools in the whole assembly process to eliminate assembly errors and ensure assembly quality.

6. When the inner hole of the sleeve is deformed, the roundness is out of tolerance, or the fit with the bearing is too loose, local electroplating can be used to compensate, and then grinding can be carried out to meet the requirements, and this method can also be used at the journal.

7. The end faces of the round nut, oil cover and other parts on the motorized spindle are in close contact with the end faces of the inner and outer rings of the bearing, so the verticality between the threaded part and the end face is very high, and the contact situation can be checked by coloring method. If the coincidence degree is 8, the assembled motorized spindle should be adjusted axially (measured with a tension spring ruler), and the static and dynamic radial runout and lifting clearance should be measured at the same time until the assembly process requirements are met.

9. Under the actual operating conditions of the machine, excluding the influence of factors such as assembly and thermal deformation when the machine is running, the rotor is dynamically balanced with a dynamic balance instrument at a certain speed.

Maintenance analysis and elimination methods of common faults of motorized spindle;

1, spindle fever

(1) The pre-tightening force of the spindle bearing is too large, which leads to the excessive friction when the spindle rotates and the spindle temperature rises sharply.

Troubleshooting: It can be eliminated by readjusting the preload of the spindle bearing.

(2) Wear or damage of the spindle bearing will also cause excessive friction when the spindle rotates, which will lead to a sharp increase in the spindle temperature.

Troubleshooting: Replace the bearing with a new one.

(3) The spindle lubricating oil is dirty or has impurities, which will also cause excessive resistance when the spindle rotates, causing the spindle temperature to rise.

Troubleshooting: clean the front of the car and change the oil again.

(4) Running out of grease or too much grease on the spindle bearing will also cause excessive resistance and friction when the spindle rotates, which will increase the temperature of the spindle.

Troubleshooting: Remove it by reapplying grease.

2. The spindle stops when cutting powerfully.

(1) The transmission belt connected between the spindle motor and the spindle is too loose, which leads to the transmission torque of the spindle is too small, and the spindle torque is insufficient during strong cutting, so an alarm is given and the CNC machine tool automatically stops.

Troubleshooting: By readjusting the tension of the spindle drive belt, it can be eliminated.

(2) There is oil on the surface of the drive belt connected between the spindle motor and the spindle, which causes the drive belt to slip when the spindle is driven, and the spindle torque is insufficient when hard cutting, so the alarm will be given and the CNC machine tool will stop automatically.

Troubleshooting: Clean with gasoline or alcohol and wipe clean.

(3) The transmission belt connecting the spindle motor and the spindle fails for a long time, which leads to the torque of the spindle motor being unable to be transmitted, and the spindle torque is insufficient during strong cutting, so an alarm is given and the CNC machine tool automatically stops.

Troubleshooting method: replace the new spindle drive belt to eliminate it.

(4) The connection between the clutch and the coupling in the spindle transmission mechanism is loose or adjusted or worn, which leads to excessive torque transmission error of the spindle motor and strong spindle vibration during strong cutting. When the alarm is generated, the CNC machine tool automatically stops.

Troubleshooting: Troubleshooting by adjusting or replacing the clutch or coupling.

3, the spindle noise is too large at work.

(1) The dynamic balance of the spindle parts is not good, which causes excessive vibration when the spindle rotates and produces working noise.

Troubleshooting: Require professionals from machine tool manufacturers to re-check and debug the dynamic balance of all spindle components.

(2) The main shaft transmission gear is worn, so that the gear meshing clearance is too large, and the impact vibration is too large when the main shaft rotates, resulting in working noise.

Troubleshooting: Require professionals from machine tool manufacturers to check, repair or replace the spindle drive gear.

(3) The supporting bearing of the spindle is brushed or damaged, so that the rotating clearance of the spindle is too large, and the impact and vibration during rotation are too large, resulting in working noise.

Troubleshooting: Ask the professionals of the machine tool manufacturer to check, repair or replace the bearings.

(4) The spindle drive belt is slack or worn, which leads to excessive friction when the spindle rotates, resulting in working noise.

Troubleshooting: eliminate the fault by adjusting or replacing the drive belt.

4. The tool cannot be clamped.

(1) The displacement of the belleville spring is too small, which leads to the spindle grasping and clamping device unable to reach the correct position and clamp the tool.

Troubleshooting method: by adjusting the stroke length of the disc spring.

(2) The spring chuck is damaged, which makes the spindle clamping device unable to clamp the cutter.

Troubleshooting method: replace the spring chuck with a new one.

(3) The disc spring fails, which leads to the spindle gripper and clamping device can't move to the correct position and can't clamp the tool.

Troubleshooting method: replace the disc spring with a new one.

(4) The pull nail on the handle is too long and collides with the spindle clamping device, which prevents it from moving to the correct position and clamping the tool.

Troubleshooting method: adjust or replace the pull nail, and correct installation can eliminate it.

5. Do not loosen the tool after clamping.

(1) Insufficient pressure and stroke of hydraulic cylinder for loosening cutter.

Troubleshooting method: by adjusting the position of hydraulic pressure and travel switch.

(2) The disc spring is pressed too tightly, so that the spindle clamping device cannot be completely moved to the correct position and the cutter cannot be loosened.

Troubleshooting method: by adjusting the nut on the disc spring and reducing the amount of spring depression.

The motorized spindle has the advantages of compact structure, light weight, small inertia, small vibration, low noise and fast response, which can reduce gear transmission, simplify the shape design of machine tools and easily realize spindle positioning. This is an ideal structure in high-speed spindle unit. As the most critical component of high-speed CNC machine tools, motorized spindle's performance largely determines the machining accuracy and production efficiency of the whole high-speed machine tools. As the core component of machining center, motorized spindle combines the spindle of machine tool and the spindle of AC servo motor into one, that is, the stator and rotor of spindle motor are directly installed in the spindle assembly. After accurate dynamic balance correction, it has good rotation accuracy and stability, forming a perfect high-speed spindle unit. Also known as the built-in motorized spindle, the geared transmission pair is no longer used, thus realizing the "zero transmission" of the machine tool spindle system, and the rotor directly drives the spindle to run after being electrified.