The planetary gearbox is a driving mechanism. Its structure is tightly combined by the inner ring gear and the gearbox housing. There is a sun gear at the center of the gear, driven by external force. These gears are evenly divided into tray planetary gear sets. The planetary gear relies on the output shaft, inner ring gear, and sun gear to support the floating cycle. The sun gear is driven by the input side, which can drive the planetary gears to rotate and move along the center trajectory of the internal gear ring. The rotational drive of the planetary gear reducer is connected to the output shaft of the tray, outputting power.

Under the condition of ensuring good concentricity between the drive motor and the reducer, the output shaft of the drive motor only bears rotational force (torque) and will remain stable without pulsation during operation. If not concentric, the output shaft of the driving motor must also withstand the radial force (bending moment) at the input end of the reducer.
This radial force will force the output shaft of the driving motor to bend, and the bending direction will continuously change with the rotation of the output shaft. When the concentricity error is large, the radial force will cause the local temperature of the output shaft of the stepper motor to rise, resulting in continuous damage to the metal structure of the motor and ultimately causing the output shaft of the driving motor to fracture due to local fatigue. The larger the concentricity error, the shorter the fracture time of the output shaft of the driving motor;
When the output shaft of the motor breaks, the input end of the reducer will also bear radial force from the output shaft of the motor. If the radial force exceeds the maximum radial load that the input end of the reducer can withstand, the input end of the reducer will deform or even break, or the supporting bearings at the input end will be damaged. So ensuring concentricity during assembly is very important! Through analysis of the assembly process, it was found that if the drive motor shaft is concentric with the input end of the reducer, the surface of the drive motor shaft and the hole surface of the input end of the reducer are at the same height, and the contact surfaces of the two are closely connected without radial force and deformation space. If the assembly is not concentric, there will be no overlap or gap between the contact surfaces, resulting in radial force and deformation space. Similarly, the output shaft of the reducer may also break or bend due to the same reasons as the motor drive shaft. However, the output of the reducer is the result of multiplying the output of the driving motor with the reduction ratio. Due to the larger output of the reducer compared to the electric motor, the output shaft of the planetary gearbox is more prone to breakage. So, when using a reducer, users should pay more attention to ensuring concentricity when installing the output end!