Planetary Gearbox

The Planetary Gear Reducer Basics

A planetary gear reducer is a special transmission mechanism that aims to transmit a maximum torque in the most compact form. Simply speaking, it is a gearbox with the input shaft and output shaft aligned within it. The planetary gear reducer decreases the number of motor revolutions and ensures high torque through the speed sensor. But how exactly does it work? In this article, we first want to discuss the structure to better understand its mechanism. Later, we will take a closer look at all its different advantages and applications.


Figure 1. Planetary Gear Reducer, SunUs


The Structural Design

The main transmission structure of the planetary gear reducer contains planetary gear, sun gear, and ring gear. The sun gear driven by an external power is located in the center of the ring gear. This device is composed of a gear (sun gear) rotating around a fixed shaft and a meshing gear (planetary gear) rotating around a sun gear. The ring gear is in close contact with the internal gearbox housing. Between the sun gear and the ring gear, there is a planetary gear set, which consists of three gears equally distributed on the so-called planet carrier.

These three gears are directly supported by the output shaft, ring gear, and sun gear, which float in it. When the sun gear is driven by the input power, the planetary gear will start to rotate around the center as well as the orbit of the ring gear.
 


Figure 2. Structural Components of a Planetary Gear Reducer
 


Superior Advantages

If you want to achieve high torque while reducing the processing speed, then a planetary gear reducer might be your ideal choice. In real life, you'll find planetary gear reducers in not only small machines like electric screwdrivers but large units like bulldozers. They are better than both helical and spur gears when it comes to efficiency, durability, and horsepower.

Now, let us look at all of the advantages of a planetary gear reducer:

1. High Power Density 
On a planetary gear reducer, several planets or airplanes share the load instead of one gear. The more of these planets are incorporated into a gearbox, the better the shared load efficiency. This leads to higher power density.


2. High Efficiency
A planetary gear reducer is highly efficient due to its unique design. Although many speed gear reducer manufacturers do not disclose efficiencies in their catalog directly, there is a simple calculation you can use to obtain the value:

Input Power/Output Power = Efficiency
 
3. Compact Size and Low Weight 
Planetary gear reducers also have a very compact design compared to other speed reducers and as a result, usually weigh less than other types. With this device, you can achieve as much as a 50% size reduction while maintaining the same torque output.

4. Durability & Longer Product Life
Thanks to the torsion rigidity and better rolling properties of planetary gear reducers, they usually last longer and are not as prone to malfunctions. Bearings help reduce the damage caused by rubbing the shaft directly on the box. Therefore, higher gear efficiency and smoother operation are achieved.

5. Increased Repeatability
Higher radial and axial load speeds provide reliability and sturdiness, which results in a significantly lower risk of gear misalignment. Besides, planetary gear reducers ensure a constant and uniform transmission and greatly reduced vibration under different loads. All these result in higher precision and therefore increased repeatability.
 
6. Increased Torque transmission
As more teeth come into contact, the mechanism can transmit and withstand greater torque. Also, a planetary gear reducer transfers the power more evenly.
 
7. Maximum Versatility
The mechanism of a planetary gear reducer is installed in a cylindrical gearbox and can be installed in almost any space. On top of that, planetary stages can be stacked which allows for high customizability.


Gearboxes Offer Endless Applications

Planetary gear reducers or gearboxes have the aforementioned benefits of compact size, lightweight design, strong load capacity, high reliability, low noise, large output torque, large speed ratio range, high efficiency, and incredible versatility. Thanks to these advantages, planetary gear reducers are suitable for lifting and transportation, construction machinery, metallurgy, mining, petrochemicals, construction machinery, light industry and textile industry, medical equipment, instrumentation, automobiles, ships, weapons, aerospace, and many other industrial sectors.

Some planetary reducers are specially designed for square flanges, with simple installation in mind, which makes them especially suitable for AC/DC servo motors, stepper motors, hydraulic motors, and others.

 

 

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