In the datasheet of a harmonic gearbox, in addition to the commonly specified rated torque, there are two other torque-related parameters, as shown below:
Many customers do not fully understand what these parameters mean. Here is an explanation:
Moment Permissible Torque
The maximum torque that the harmonic gearbox can withstand for a short period. It is specifically designed to handle unexpected impacts, emergency stops, or sudden mechanical jams. The allowable duration is usually extremely short. For a single occurrence, it is recommended to keep the duration within a few milliseconds to several tens of milliseconds to avoid exceeding the torsional limit of the flexspline inside the gearbox.
Peak Start-Stop Torque
When the motor starts rotating (accelerating) or suddenly stops (decelerating), the impact force caused by inertia can be much greater than the force during normal steady operation. This parameter represents the maximum torque limit that the gearbox can withstand during the instant of starting or stopping.
This parameter determines how quickly the equipment can accelerate and decelerate. If this peak value is exceeded frequently, the flexspline of the harmonic gear is highly likely to experience fatigue fracture or slipping.