The Secrets of Rotational Precision: Functions and Benefits of Planetary Reducers

In a previous article titled " Mastering the Power of Planetary Gear Reducers: Ten Features of Planetary Gear Reducers You Need to Know ", we discussed ten characteristics of planetary gearboxes. Among them, one significant advantage was "improved precision". This article delves deeper into why planetary gearboxes can enhance rotational precision.

 

Compared to other types of gear transmission gearboxes, planetary gearboxes exhibit superior meshing precision between gears. The gear backlash can be reduced to less than 1 arcminute (arcmin), categorizing them as high-precision gearboxes. Furthermore, due to the gear reduction ratio, the motor needs to increase its rotation angle so that the output end can reach its final angle. As the motor increases its rotation angle, it needs to increase the output pulses, which in turn improves rotational precision.

 

Servo Motor Precision:

The control precision of a servo motor is ensured by the encoder located at the rear end of the motor shaft. For every 131,072 pulses received by the driver, the motor's output shaft completes one rotation. This means the pulse equivalent is 360°/131,072=9.89, which can also be interpreted as the motor's output shaft rotating 9.89 seconds (or approximately 0.00275°) for every pulse received by the driver.

 

Pulse Count Calculation:

For simplicity, let's assume the motor produces 10 pulses per full rotation.

One full rotation of the servo motor output shaft = 10 Pulses. One full rotation of the output shaft with a 5:1 gear reducer = 10×5=50 Pulses.

(A) Motor pulse count (pulse/revolution)	(B) Terminal output revolutions	(C) Gear reducer ratio	(D) Servo motor output revolutions (B)x(C)	(E) Output shaft rotation angle (B)x360	(F) Pulses per revolution of output shaft (pulse) (A)x(D)	Precision (degree/pulse) (E) / (F)
10	1	1(Not using gearbox)	1	360	10	36
	1	3	3	360	30	12
	1	4	4	360	40	9
	1	5	5	360	50	7.2
	1	7	7	360	70	5.143
	1	10	10	360	100	3.6

 

Servo Motor Precision:

Below, six diagrams are used to visually represent the differences in rotational precision, making the variations instantly recognizable.

Conclusion:

As illustrated above, the higher the reduction ratio, the more turns the output shaft needs for the servo motor to input. This results in a greater number of pulses. Hence, the resolution of the output shaft rotating one circle increases. This allows for finer and more precise rotations, naturally enhancing accuracy.

 

If you wish to learn more about planetary gearboxes or have any questions regarding their applications and usage, please do not hesitate to contact us. You are welcome to call or email GearKo in Taiwan.