The heating of the spindle of a CNC vertical lathe may be caused by many factors. Here are some of the main reasons:

1. Bearing damage: Damage to the spindle bearings of CNC vertical lathes may cause increased friction, which in turn generates more heat and increases the temperature of the spindle.

2. Insufficient or improper lubrication: The lubrication of the CNC vertical lathe spindle is an important factor in maintaining its normal operation and reducing friction. If the amount of lubricating oil is insufficient, or the viscosity of the lubricating oil used is too high or too low, it may cause the spindle temperature to rise. In addition, if foreign matter such as rags and cotton threads are left in the spindle box when cleaning and changing the oil of the CNC vertical lathe, it will also reduce the lubrication performance and cause the spindle temperature to rise.

3. Seal problems: Improper selection or installation of CNC vertical lathe seals may lead to oil leakage and oil cutoff, which will affect the lubrication and cooling effects of the spindle and increase its temperature.

4. Spindle motor or control module failure: These failures of CNC vertical lathe may cause the spindle to operate abnormally and generate additional heat.

5. Spindle circuit problem: If the CNC vertical lathe is partially short-circuited, it may cause the spindle motor to overheat, causing the spindle temperature to rise.

6. Overload operation of machine tools: Long-term overload operation of CNC vertical lathes may cause premature wear of machine tools and increase the temperature of the spindle.

7. Bearing clearance problem: The contact points on the surface of the shaft tile are small, the contact surface is insufficient, or the increase in bearing clearance is much greater than the clearance required by the design, which may lead to poor lubrication, which in turn causes the temperature of the spindle to rise.

In order to avoid problems caused by the heating of the spindle, CNC vertical lathes need to regularly check the lubrication of the spindle, the integrity of the seals, the wear of the bearings, etc., and replace seriously worn parts in a timely manner. At the same time, ensure that the CNC vertical lathe operates within the load range to avoid long-term overload work. When servicing and replacing parts, manufacturer's guidelines should be followed to ensure proper installation and adjustment.

Please note that the above are only possible reasons, and the specific situation of the CNC vertical lathe may require further inspection and diagnosis. If the spindle continues to heat up, it is recommended to contact professional maintenance personnel for inspection and repair.