A planetary gearbox is a transmission device that uses a planetary gear structure to reduce speed and increase torque. Due to its compact structure, high load capacity, and high efficiency, it is widely used in robotics, AGVs, machine tools, packaging machinery, and industrial automation equipment.

Working principle of a planetary gearbox
A planetary gearbox mainly consists of a sun gear, planet gears, planet carrier, and internal ring gear. Its operating principle is similar to the way planets rotate around the sun in the solar system.

How it works
The motor drives the sun gear (center gear) to rotate. The sun gear then drives multiple planet gears. These planet gears revolve around the sun gear while being carried by the planet carrier. At the same time, the planet gears mesh with the internal ring gear. Finally, the rotational power is output through the planet carrier, achieving speed reduction and torque multiplication.

Why it can reduce speed and increase torque
When the input shaft rotates at high speed, the planet gears distribute the load evenly, allowing the system to handle higher torque. Different gear tooth ratios reduce the output speed, while torque is increased proportionally according to the reduction ratio. This is the core reason planetary gearboxes are widely used in high-performance motion systems.

Reduction ratio formula
The common single-stage planetary gearbox reduction ratio is:

i = 1 + Z_ring / Z_sun

Example:
Ring gear: 72 teeth
Sun gear: 24 teeth

i = 1 + 72 / 24 = 4

This means the reduction ratio is 4:1.

Advantages of planetary gearboxes
Compact structure – high power density in a small size
High load capacity – multiple planet gears share the load
High transmission efficiency – up to 95%–98%
High precision – low backlash
Long service life – even load distribution reduces wear
Low noise – smooth gear meshing

Typical applications
Planetary gearboxes are commonly used in robot joints, AGV drive systems, CNC machine tools, servo motor systems, and packaging automation equipment.