A gearbox, also known as a reduction gearbox, is a device commonly used in mechanical transmission systems. Its function is to convert the input speed and torque from a motor or other power source into an output speed and torque suitable for a specific application.
By using different gear combinations, a gearbox can achieve various speed ratios and torque outputs, making it an essential component of mechanical transmission systems. Its primary role is to reduce speed and increase torque.
NOTE: Gearboxes do not generate torque; they only transmit it.
The rated torque of a gearbox refers to the maximum continuous torque it is designed to withstand. Exceeding this torque may cause damage or failure. The instantaneous allowable torque refers to the maximum torque the gearbox can withstand for a short duration, typically a few seconds or less. This value depends on the gearbox's design, material selection, and the load and operating conditions it must endure.
Under normal operating conditions, the output torque should remain below the rated torque to ensure reliable operation and adequate service life.
The actual output torque of a geared motor is the torque delivered at the gearbox output shaft after the motor is coupled to the gearbox. It can be calculated using the following formula:
Gearbox Output Torque = Motor Torque × Reduction Ratio × Gearbox Efficiency
Take the 17HS15-1584S-MG10 as an example. This product pairs a 17HS15-1584S stepper motor with an MG17-G10 gearbox.
The torque values before and after the gearbox is installed are shown in the table below:
| Motor Speed (RPM) | Motor Torque (Nm) | Gearbox Output Speed (RPM) | Geared Motor Torque (Nm) | Calculated Torque (Motor Torque × Gear Ratio × Efficiency) |
|---|---|---|---|---|
| 10 | 0.3259 | 100 | 2.49 | 2.9331 |
| 15 | 0.31 | 150 | 2.62 | 2.79 |
| 20 | 0.31 | 200 | 2.8 | 2.79 |
| 25 | 0.29 | 250 | 2.53 | 2.61 |
| 30 | 0.26 | 300 | 2.23 | 2.34 |
| 35 | 0.24 | 350 | 1.98 | 2.16 |
| 40 | 0.19 | 400 | 1.73 | 1.71 |
| 45 | 0.19 | 450 | 1.49 | 1.71 |
| 50 | 0.15 | 500 | 1.54 | 1.35 |
As shown, the actual output torque of the geared motor is generally consistent with the calculated values. Therefore, when high torque is required, you can flexibly select different motor and gearbox combinations with appropriate reduction ratios.
Does a larger reduction ratio always mean greater output torque?
The answer is no. When selecting a gearbox, a higher reduction ratio does not automatically result in greater usable output torque. The theoretical value calculated by the formula must not exceed the rated torque of the gearbox; otherwise, it will reduce the service life and may even cause permanent damage.