Motorized Spindle’s Maintenance And Repair
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Motorized Spindle’s Maintenance And Repair


The motorized spindle is the last ten years in the field of CNC machine tools will machine tool spindle and spindle motor integration of new technology. It is the “core” components of high-speed CNC machine tools, its performance directly determines the high-speed machining performance of machine tools.

As motorized spindles are high-speed precision components regular maintenance is very necessary. The motorized spindle is maintained as follows:

1. The radial runout of the inner cone hole of the motorized spindle is generally required to be 0.002mm(2 m) and detected twice a year.

2. The radial runout of the far end of the spindle (250mm) is generally required to be 0.012mm(12 m) and tested twice a year.

3. The extended distance of broach is 10.5±0.1mm when the broach is released (take HSK63 as an example) for 4 times a year.

Analysis and treatment of severe heating during high-speed rotation of spindle:

Heat and temperature rise in spindle operation is always the focus of research. There are two main heat sources inside the spindle unit: one is the spindle bearing, the other is the main motor.

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

Spindle bearing is the core 2113 core support of motorized spindle and also one of the main heat sources of the motorized spindle. At present, high-speed motorized spindles are mostly made of angular contact ceramic ball bearings. Because ceramic ball bearings have the following characteristics:

1. Because of the lightweight of the ball, the centrifugal force is a small, a small moment of dynamic friction.

2. Small thermal expansion caused by temperature rise, so that the bearing pre-tightening force stability.

Small elastic deformation, high stiffness, long life. Due to the high running speed of the motorized spindle, there are strict requirements for the dynamic and thermal performance of spindle bearing. Reasonable preload, good and sufficient lubrication is necessary to ensure the normal operation of the spindle.

Oil mist lubrication is adopted. The air pressure of the atomizing generator is 0.25~ 0.3mpa. 20# turbine oil is selected. The lube mist, while fully lubricating the bearings, also carries away a lot of heat. The distribution of lubricating oil in the front and rear bearings is a very important issue and must be strictly controlled. The inlet section is larger than the sum of the sections of the front and rear injection orifices, and the exhaust shall be smooth. The injection Angle of each injection hole is 15O with the axis so that the oil mist is directly sprayed into the bearing working area.

Key Points Of The Motorized Spindle Maintenance Process

1. According to the damage of the motorized spindle, measurement of static, dynamic radial runout and lift clearance, and axial movement momentum.

2. Remove the motorized spindle with a special tool made of 5261. Clean and measure rotor pendulum and wear.

3. Optional bearing. The consistency error of the inner hole and outer diameter of each group of bearings shall be ≤0.002~0.003mm. Keep a clearance of 0.0025~0.005mm from the main shaft. In practice, it is best to use both thumbs to push the bearing into the sleeve. Too tight will cause bearing outer ring deformation, bearing temperature rise is too high, too loose will reduce the stiffness of the grinding head.

4. Bearing cleaning is to ensure the normal work and service life of the important link, do not use compressed air to blow the bearing, because the compressed air in the hard particles will make the racetrack hair.

5. Tapered bearings or angular contact ball bearings must pay attention to the direction of bearing installation, otherwise, they can not reach the rotary precision requirements. The whole assembly process adopts special tools 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 it is too loose with the bearing. The local electroplating method can be used to compensate and regrind to the requirement, and this method can also be used at the shaft neck.

7. The end face of the round nut and oil seal cover on the motorized spindle is in close contact with the end face of the inner and outer rings of the bearing respectively. Therefore, the perpendicularity of the threaded part and the end face is very high. If the contact rate & LT;80%, can grind the end face, make it reach perpendicularity requirement.4102 this work is very important. Its accuracy will affect the radial runout of the grinding spindle extension rod, thus affecting the surface roughness of the grinding workpiece.

8. The spindle shall be adjusted in axial direction after assembly (measured by tension spring balance during adjustment). At the same time, static and dynamic radial run-out and lifting clearance shall be measured until the assembly process requirements are met.

9. Under the actual running conditions of the machine, excluding the influence of assembly. Thermal deformation, and other factors during the operation of the machine, under a certain rotating speed, a dynamic balancing instrument is used to balance the rotor in motion.

Maintenance Analysis And Elimination Method Of Common Faults Of Motorized Spindle

1. Spindle heating

(1) The spindle bearing preload is too large, causing the spindle rotation friction too large, causing the spindle temperature sharply increased.

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

(2) Spindle bearing grinding or damage will also cause spindle rotary friction too large, resulting in a sharp rise in spindle temperature.

Troubleshooting: It can be eliminated by replacing new bearings.

(3) Spindle oil dirty or impurities will also cause spindle rotation resistance is too large, causing spindle temperature rise.

Troubleshooting: remove the problem by cleaning the headstock and changing the oil.

(4) When the lubricating grease of spindle bearing is exhausted or too much lubricating grease, it will also cause the resistance and friction of spindle turning to be too large, which will cause the temperature of the spindle to rise.

Troubleshooting: Remove by reapplying grease.

2. Spindle when the strong cutting stop

(1) The transmission belt connecting the spindle motor and the spindle is too loose, resulting in too small spindle drive torque, insufficient spindle torque during strong cutting, the alarm will be generated, and the CNC machine will stop automatically.

Troubleshooting methods: By adjusting the tension of the main shaft belt, to eliminate.

(2) There is oil on the surface of the transmission belt between the spindle motor and the spindle, which causes the transmission belt to slip when the spindle is driving. In the case of strong cutting, the spindle torque is insufficient, giving an alarm and the CNC machine stops automatically.

Troubleshooting: Remove by scrubbing after cleaning with gasoline or alcohol.

(3) The driving belt connecting the spindle motor and the spindle becomes invalid after being used for too long, which causes the spindle motor’s torque to be unable to drive. When the spindle torque is insufficient during strong cutting, an alarm will be generated and the CNC machine will stop automatically.

Troubleshooting: remove the fault by replacing a new spindle drive belt.

(4) In the spindle driving mechanism, the clutch, coupling connection, adjust too loose or wear, resulting in the spindle motor torque transmission error is too large, strong vibration spindle cutting. Generate alarm, NC machine automatically stops.

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

3. Too much noise when the spindle works

(1) Poor dynamic balance of spindle components, so that the spindle rotation vibration is too large, causing working noise.

Troubleshooting methods: All spindle components should be checked and adjusted by professionals from the machine tool manufacturer.

(2) Spindle transmission gear wear, so that the gear meshing clearance is too large, spindle rotation impact vibration is too large, causing work noise.

Troubleshooting: it is necessary to have the spindle drive gear inspected, repaired, or replaced by a professional from the machine tool manufacturer.

(3) Spindle bearing drawing or damage, so that the spindle rotary clearance is too large, rotary impact, vibration is too large, causing work noise.

Troubleshooting: Professional personnel from the machine tool manufacturer are required to inspect, repair, or replace the bearings.

(4) The spindle belt slack or wear, so that the spindle rotary friction too large, causing work noise.

Troubleshooting: remove by adjusting or replacing the belt.

4. The tool cannot be clamped

(1) The displacement of the dish spring is too small so that the spindle grasping knife, clamping device cannot reach the correct position, the tool cannot be clamped.

Troubleshooting: by adjusting the stroke length of the spring dish to eliminate.

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

Troubleshooting: remove the problem by replacing the spring chuck.

(3) Disc spring failure, so that the spindle grasp knife, clamping device can not reach the correct position, the tool can not be clamped.

Troubleshooting: remove the problem by replacing a new dish spring.

(4) The pull nail on the handle is too long and hits the grasping knife and clamping device of the spindle, making it unable to move to the correct position and the tool cannot be clamped.

Troubleshooting methods: By adjusting or replacing the pull nails, and correct installation to remove.

5. Do not loosen the tool after it is clamped

(1) Release hydraulic cylinder pressure and stroke is not enough.

Troubleshooting methods: By adjusting the hydraulic pressure and stroke switch position to eliminate.

(2) Saucer spring pressing is too tight so that the spindle clamping device cannot fully move to the correct position, and the tool cannot be released.

Troubleshooting: by adjusting the nut on the dish spring, reduce the spring pressure to eliminate.

1653 electric spindle for a high-speed CNC machine tool is the most key component, its performance depends to a large extent determines the processing accuracy and production efficiency of the high-speed machine tools, electric spindle as the core component of the machining center. It will close 2 for one, machine tool spindle and ac servo motor shaft of the spindle motor stator and rotor directly into the interior of the spindle component, and through the accurate dynamic balancing correction, have good rotation accuracy and stability, forming a perfect high-speed spindle unit, also known as the built-in motorized spindle, it no longer USES the belt gear transmission, so as to realize the “zero transmission” of machine tool spindle system. After energizing, the rotor drives the spindle directly.

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