(1) outer ring fits tightly;
(2) parts and shape and position tolerance problem, parts such as the frame, end cap, shaft concentricity is not good;
(3) improper selection of bearings;
(4) poor lubrication of the bearing or bearing cleaning dirty, grease with debris;
The use of:
(1) unit of improper installation, the motor shaft and drag the mechanism of the shaft concentricity is not required;
(2) the pulley pulled too tight;
(3) bearing bad maintenance, grease or over use, dry metamorphism.