In the manufacturing process of the motor, the interference of the shaft and the rotor core has a great influence on the plane of the core punching plate, especially on the flatness of the motor with a radial air passage of the rotor, resulting in uneven alignment of the stator core. The length of the effective iron core cannot be guaranteed, resulting in a large no-load current of the motor and a decrease in the power factor. If the air flow is blocked, the motor temperature rises.
　　Flatness refers to the amount of change in the actual surface of its ideal plane. The unit of flatness is as specified in the drawings. The general unit is mm. Flatness error is to compare the actual surface to be measured with the ideal plane. The distance between the two is the flatness error.
　　The clearance between the rotor shaft and the rotor core is too large, or it is caused by too-smooth machining of the rotor shaft during production. This phenomenon occurs because the rotor core of the motor accelerates too fast, or the torque of the rotor shaft of the motor is greater than the friction between the rotor shaft and the rotor core. In order to prevent this phenomenon, a larger motor will press the iron core and the shaft of the rotor and fix it by spot welding. Related reading: Operation steps of the rotor core of the motor
　　In order to maintain the flatness of the punching plate in the motor core and ensure the quality of the motor, it is necessary to carry out experimental research and analysis of the interference between the motor shaft and the rotor core; it is necessary to determine a reasonable amount of interference and process methods, and to ensure the shaft and iron. The core can not be loosened, so as to improve the manufacturing quality of the motor.