How to judge whether the bearing of COLD MILL Motor is short of oil?

1. Judge by listening to the sound
Normal sound characteristics: When the COLD MILL Motor bearing is well lubricated, the running sound is relatively smooth, low and continuous. This is because the right amount of lubricating oil forms a good lubricating film between the ball, raceway and cage of the bearing, making the friction and collision between the components relatively slight.
Oil shortage sound performance: If the bearing is short of oil, it will emit a sharper "hissing" sound or intermittent "chirping" sound during operation. This is due to insufficient lubrication, increased friction between the ball and raceway, and increased probability of direct contact between metal parts, resulting in this abnormal friction sound. As the oil shortage situation worsens, the sound may become more piercing and the frequency of occurrence will also increase.
2. Observe temperature changes
Normal temperature range: Under normal operating conditions, the temperature of COLD MILL Motor bearings is usually higher than the ambient temperature by a certain range. Generally speaking, the normal temperature increase is about 15-30℃. For example, if the ambient temperature is 25℃, the normal operating bearing temperature may be between 40-55℃. This is because under good lubrication conditions, the frictional heat generated inside the bearing can be effectively controlled through the circulation and conduction of the lubricating oil and the heat dissipation system of the motor itself.
Temperature abnormality caused by lack of oil: When the bearing lacks oil, the heat generated will increase due to increased friction. At this time, the bearing temperature will rise significantly and may exceed the normal temperature range by more than 10-15℃. An infrared thermometer can be used to monitor the bearing parts regularly (for example, once an hour). If the temperature continues to rise and exceeds the normal range, it is likely that the bearing is lacking oil or poor lubrication.
3. Check the grease status (if it can be observed)
Normal grease status: For bearings where the grease can be directly observed (partial open bearings or bearings with inspection windows), normal grease should be evenly distributed inside the bearing, soft in texture and have a certain gloss. Grease can form a complete oil film between bearing components, which plays a good role in lubrication and heat dissipation.
Grease characteristics when lacking oil: If the bearing lacks oil, the grease may dry up and harden. The originally soft grease becomes dry and hard, losing its proper viscosity and fluidity. Or you can see that the amount of grease is significantly reduced and cannot completely cover the key parts of the bearing such as the ball and raceway. This situation indicates that the bearing needs to be relubricated.
4. Performance change detection
Vibration: Under normal lubrication conditions, COLD MILL Motor runs relatively smoothly and the vibration amplitude generated by the bearing is small. A vibration sensor can be used to detect the vibration of the motor. When the bearing is short of oil, the vibration amplitude of the motor will increase significantly due to uneven friction and increased collision between components. Usually, an increase in high-frequency components in the vibration spectrum can be observed, because the impact vibration between the ball and the raceway is more frequent.
Response to motor load changes: Under normal circumstances, when the motor load changes, the bearing can use the buffering effect of the lubricating oil to make the motor adapt to the load change more smoothly. If the bearing is short of oil, when the motor load changes (such as the rolling force of the cold rolling mill changes), the motor speed may fluctuate, or the running sound and vibration of the motor may change suddenly. This is because the bearing cannot effectively reduce friction and buffer impact when it is short of oil, resulting in poor adaptability of the motor to load changes.