1, the rotor shaft is not concentric: the gap between the shaft and the bearing bush is too large, mainly because the fan blades collide and squeeze, and the dynamic balance is destroyed, causing jitter and long-term wear.

2. The fan is poorly maintained and runs without lubrication for a long time.

3. If the end cover is deformed or the briquette is loose, the elimination method can be to open the rear end cover and take out the rotor. Check the clearance between the tile and the shaft. If the gap is too large, it cannot be used. If the bearing bush is seriously damaged and the rotor shaft is worn, please replace it with a new one.