Various failures of 13 servo motor include motor rotation, motor position error, motor torque reduction, motor vibration, motor jump, motor creep, motor encoder phase failure, motor commutator failure, motor carbon brush failure, motor speed control, motor overheating, motor phase imbalance, and work before starting the servo motor. A, the servo motor does not turn, the common diagnosis method is to check whether the numerical control system has pulse signal output and whether the enable signal is connected. Check whether the specification error of the motor position error system is too small, and check whether the load is too large if the motor torque decreases. Looking for the problem of speed loop in motor vibration inspection. Check the motor movement is generally caused by the reverse clearance of the feed transmission chain or excessive servo drive gain. Second, the motor creeps. Check the looseness of the connecting parts or the defects and cracks of the coupling itself. The phase servo driver of the motor encoder reads the single-lap position value of the absolute encoder and stores it in EEPROM, which records the initial phase of the electric angle of the motor inside the encoder. Motor commutator faults can be processed by precision machine tools. Thirdly, if there are more than four big sparks when the motor carbon brush fails, it is necessary to polish the commutator with sandpaper and replace the carbon brush. The speed of the control motor is controlled by the control circuit board. Motor overheating: check whether the bearing is poorly lubricated or cleaned. There are impurities in the grease. Check the motor phase imbalance for poor welding or poor contact of internal phase branches of the motor, short circuit between motor windings or short circuit to ground. Before working, start the servo motor to check whether the power supply, grounding and fuse are normal.