Causes: ① Too much or too little grease; ② Poor oil quality containing impurities; ③ Improper fit between the bearing and the shaft neck or end cap (too loose or too tight); ④ The bearing bore is eccentric, rubbing against the shaft; ⑤ The motor end cap or bearing cap is not flush; ⑥ The coupling between the motor and the load is not aligned, or the belt is too tight; ⑦ The bearing clearance is too large or too small; ⑧ The motor shaft is bent.

Troubleshooting: ① Add grease as specified (1/3-2/3 of the volume); ② Replace with clean grease; ③ If it's too loose, use adhesive to repair it; if it's too tight, turn it and grind the shaft neck or end cap bore to make it fit; ④ Repair the bearing cap to eliminate any rubbing; ⑤ Reassemble; ⑥ Realign and adjust the belt tension; ⑦ Replace the bearings; ⑧ Align the motor shaft or replace the rotor.