Bearing precision is low: choose the specified precision grade bearing.
Spindle bending or box hole is not centered: repair the spindle or box.
Poor lubrication: choose the specified grade of lubrication materials and proper cleaning.
Low assembly quality: improve assembly quality.
Running rings in the inner shell of the bearing: replace the bearing and related wear parts .
Axial force is too large: clean, adjust the sealing mouth ring clearance requirements between 0.2 ~ 0.3mm, correct the impeller balance hole diameter and check the static balance value.
Bearing damage: replace the bearing.