When the output force of a planetary gearbox is too low, resulting in a broken shaft, there may be several reasons:

1.Overload: The planetary gearbox is subjected to a load greater than its rated capacity. If the gearbox needs to provide more torque than it is designed to handle, the shaft may break. This may be due to excessive load or torque overload due to a sudden impact of the load or unexpected circumstances.

2.Insufficient power: If the input power of the gearbox is not sufficient to provide enough torque to drive the load, then the load will produce too much resistance, resulting in shaft breakage. This may be caused by incorrect motor selection, unstable power supply voltage, or motor failure.

3.Incorrect design or manufacturing defects: There may be problems with the design or manufacture of the planetary gearbox, such as incorrect shaft size, improper material selection, or defects in the manufacturing process. These problems may cause the shaft to break during operation.

4.Improper installation or maintenance: Improper installation or maintenance can also cause shaft breakage. For example, incorrect axial alignment, loose mounting bolts, and insufficient lubrication can all cause shaft breakage

To prevent shaft breakage, the following measures can be taken:

1.Make sure the load on the planetary gearbox does not exceed its rated capacity and that the load is rated and controlled.

2.Ensure that the input power of the gearbox meets the operating requirements and make necessary motor

selection and adjustments.

3.Ensure that the design and manufacturing of the planetary gearbox are of high quality and select appropriate shaft sizes and materials.

4.Ensure the correct installation and maintenance of the gearbox, including axial alignment, regular inspection of mounting bolts, and lubrication maintenance.

Source:https://blog.aujourdhui.com/tianqiong2019/2705161/causes_of_shaft_breakage_in_planetary_gearboxes.html#non