Problem Description: Intense heat generation occurs during high-speed spindle rotation and machining. Heat generation and temperature increase issues during the operation of the electric spindle have always been a focal point of research. The two primary heat sources within the electric spindle assembly are the spindle bearings and the integrated main motor. In the case of a protruding spindle unit, the heating of the built-in main motor becomes particularly prominent. Given its proximity to the main motor, if the motor's heat dissipation is not properly addressed, it could compromise the reliability of the machine tool's operation. The main solution involves implementing a circulating cooling system, which can be either external or internal. The cooling medium may be water or oil, ensuring comprehensive cooling for both the motor and the front and rear bearings.
The spindle bearing serves as the core support for the electric spindle and is also one of its primary heat sources. Most high-speed electric spindles currently employ angular contact ceramic ball bearings. These bearings possess several advantages: their lightweight design results in reduced centrifugal force and minimal dynamic friction torque; the thermal expansion caused by temperature increases remains small, keeping the bearing preload force stable; they exhibit low elastic deformation, high rigidity, and extended lifespan. Given the high operational speeds of the electric spindle, stringent demands are placed on the dynamic and thermal performance of the spindle bearing. Proper preload force and adequate lubrication are essential for maintaining spindle functionality. Oil mist lubrication is utilized, with the atomizer generator intake pressure set between 0.25-0.3MPa, using 20# turbine oil, and controlling the oil drop rate at 80-100 drops per minute. While providing comprehensive lubrication for the bearings, the oil mist also helps dissipate significant amounts of heat. The distribution of lubricating oil across the front and rear bearings is a crucial matter that must be carefully managed. The cross-sectional area of the air inlet should exceed the combined cross-sectional areas of the front and rear oil injection ports, ensuring smooth exhaust. The injection angle of each port should be at a 15-degree angle to the axis, allowing the oil mist to be directly sprayed into the bearing's working area.
Analysis and Troubleshooting of Common High-Speed Electric Spindle Failures:
Spindle Heating:
1) Excessive preload force on the spindle bearing leads to heightened friction during spindle rotation, causing a sharp rise in spindle temperature. This can be resolved by readjusting the preload on the spindle bearing.
2) Damage or deterioration of the spindle bearing also results in excessive friction during spindle rotation, causing a rapid rise in spindle temperature. This issue can be resolved by replacing the bearing with a new one.
3) Dirty or contaminated spindle lubricating oil can lead to increased resistance during spindle rotation, causing the spindle temperature to rise. This can be addressed by replacing the oil and cleaning the spindle housing.
4) Insufficient or depleted lubricating grease in the spindle bearing can also cause excessive resistance and friction during spindle rotation, leading to a rise in spindle temperature. This can be resolved by reapplying grease.
Spindle Stopping During Strong Cutting:
1) A loose transmission belt connecting the spindle motor and the spindle results in insufficient transmission torque, inadequate spindle torque during strong cutting, triggering an alarm, and automatic shutdown of the CNC machine. This can be resolved by readjusting the tension of the spindle drive belt.
2) Oil on the surface of the transmission belt connecting the spindle motor and the spindle causes slippage during spindle transmission, insufficient spindle torque during strong cutting, triggering an alarm, and automatic shutdown of the CNC machine. This can be resolved by cleaning with gasoline or alcohol.
3) A worn-out transmission belt connecting the spindle motor and the spindle cannot transmit the motor's torque, leading to insufficient spindle torque during strong cutting, triggering an alarm, and automatic shutdown of the CNC machine. This can be resolved by replacing the spindle drive belt.
4) Loose or worn clutches and couplings in the spindle transmission mechanism result in significant torque transmission errors and strong vibrations during strong cutting, triggering an alarm and automatic shutdown of the CNC machine. This can be resolved by adjusting or replacing the clutch or coupling.
Excessive Noise During Spindle Operation:
1) Poor dynamic balance of the spindle components causes excessive vibration during spindle rotation, leading to operational noise. This requires professional inspection and adjustment of all spindle components by the machine tool manufacturer.
2) Wear on the spindle transmission gears results in excessive gear meshing clearance, causing significant impact and vibration during spindle rotation, leading to operational noise. This requires inspection, repair, or replacement of the spindle transmission gears by professionals from the machine tool manufacturer.
3) Burping or damage to the spindle support bearings causes excessive rotational clearance and significant impact and vibration during rotation, leading to operational noise. This requires inspection, repair, or replacement of the bearings by professionals from the machine tool manufacturer.
4) Looseness or wear on the spindle transmission belt causes excessive friction during spindle rotation, leading to operational noise. This can be resolved by adjusting or replacing the drive belt.
Failure to Clamp the Tool:
1) Insufficient displacement of the disc spring prevents the spindle tool gripping and clamping device from reaching the correct position, preventing the tool from being clamped. This can be resolved by adjusting the length of the disc spring.
2) Damage to the spring chuck renders the spindle clamping device incapable of clamping the tool. This can be resolved by replacing the spring chuck with a new one.
3) Failure of the disc spring prevents the spindle tool gripping and clamping device from moving to the correct position, preventing the tool from being clamped. This can be resolved by replacing the disc spring with a new one.
4) A long nail on the handle strikes the spindle gripping and clamping device, preventing it from moving to the correct position and preventing the tool from being clamped. This can be resolved by adjusting or replacing the nails and correctly installing them.
In conclusion, addressing these common issues with high-speed electric spindles requires careful attention to detail and professional intervention when necessary. Proper maintenance and timely repairs are essential to ensure optimal performance and longevity of the spindle.
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