How to determine the appropriate reduction ratio when selecting FBR series planetary reducer

To select the appropriate reduction ratio for the FBR series planetary gearbox, a systematic calculation and verification process needs to be followed. The core lies in balancing the speed and torque requirements of the load, and ensuring a perfect match with the motor.

The following are the four core steps to determine the appropriate reduction ratio:

Step 1: Clarify the speed requirement of the load

Firstly, you need to determine the actual operating speed (n ₂) required at the load end of the equipment (i.e. the output end of the gearbox). This is usually determined by your production process or equipment design requirements.

For example, a conveyor belt drum needs to reach 955 revolutions per minute, or a worktable driven by a screw needs to reach 3000 revolutions per minute. This value is the basis for calculating the reduction ratio.

Step 2: Determine the rated speed of the motor

Next, confirm the rated speed (n ₁) of the servo motor or stepper motor you plan to match. When calculating, the rated speed of the motor should be used instead of the maximum speed.

Common motor speed reference:

1. Servo motor: usually 3000 rpm

2. Three phase asynchronous motor (4-pole): typically 1450 rpm

3. Stepper motor: usually in the range of 600-1500 rpm

Step 3: Calculate the theoretical reduction ratio

After determining the load speed (n ₂) and motor speed (n ₁), the theoretical reduction ratio (i) can be calculated.

1. Calculation formula:

Reduction ratio (i)=rated motor speed (n ₁)/required load speed (n ₂)

2. Calculation example:

If your servo motor has a rated speed of 3000 rpm and the required speed at the load end is 100 rpm, then the theoretical reduction ratio is:

i = 3000 / 100 = 30

This means you need to choose a gearbox with a speed ratio of 30.

Step 4: Verify torque matching (crucial!)

Merely meeting the speed requirements is not enough, it is necessary to verify whether the output torque of the gearbox can meet the load demand at this reduction ratio. This is a key step to avoid the equipment being "powerless" or the motor being overloaded and burned out.

1. Calculate theoretical output torque:

The theoretical output torque (Toutput) of the reducer is determined by the rated torque of the motor (Tmotor), the reduction ratio (i), and the transmission efficiency of the reducer (η, usually taken as 0.95-0.98).

Theoretical output torque (Toutput)=motor rated torque (Tmotor) × reduction ratio (i) × transmission efficiency (η)

2. Verify safety margin:

The calculated theoretical output torque must be greater than the actual torque required by the load (T-load), with sufficient safety margin. Usually, we require:

Theoretical output torque (Toutput) ≥ load torque (Tload) × safety factor

Safety factor: It is recommended to take 1.2-1.5 under general working conditions; For heavy load conditions with frequent start stop and impact, the safety factor should be taken as 2.0 or higher.