The commutator is the weak link on the motor and is the main object of regular maintenance of the motor. Check the commutator to check the degree of wear and out of roundness; check the short circuit and burning phenomenon; check whether the surface is smooth, when the surface height difference is greater than 0.5mm, the armature should be extracted for turning, and the mica sheet on the commutator should be 0.5mm below the commutator; check if the brush is loose and too tight in the frame, the distance between the commutator surface and the brush box should be 3 mm ~ 5 mm.