Planetary Gearbox

Planetary Gearboxes are a form of the gearbox where the output and input both have the same center of turning. This means that the center of the input gear rotates around the center of the output section, and the output and input shafts are aligned.


Planetary Gearbox Guarantees Flexible & Reliable Power Transmission System


Wide Speed Ratio with a Long Service Lifespan


Compact Size & Lightweight


Unique Design for High Power Density


High Accuracy

Transmission structural components of planetary gearboxes

A planetary gearbox is a mechanical device consisting of sun gear, the planet gears, the planet gears’ carrier, and the ring gear. Sun gear located at the centre that transmits torque to planet gears orbiting around the sun gear. Planet and the sun gear are located inside the ring gear.

Sun Gear

The sun gear drives the surrounding planetary gears which are fixed to a carrier in order to avoid slipping during operation. As the sun gear is driven, the planetary gears rotate the ring gear (also known as outer gear).

Planet Gears

Usually, the planetary gear has two gears, one planet gear meshes with the sun gear, while the other meshes with the planetary ring gear. These are used as speed reducers. They are used to slow down motor gearboxes and increase torque.


Planet Carrier

The planet carrier holds the planet gear which rotates around itself with a rotation that is the opposite of the planet carrier. It usually connects the centers of two gears and provides support for them to roll without slipping.

Ring Gear

The load from the sun gear is distributed to several planet gears that are used to drive either the outer ring, shaft, or spindle. The ring gear rotates in the same direction as the sun gear, thus providing a reverse direction.

Advantages of using planetary gearboxes

The planetary gear reducers can withstand higher torque than other types of speed reducers under the same volume.


High torque density


Wide range of reduction ratio


High precision


High efficiency and Low noise

How to choose a planetary gearbox?

There are many brands and models of planetary gearboxes, and each of them has its own unique features and applications. It is easy to buy a good product, but picking up the one that fits is difficult. Mainly consider the following factors.


Frame sizes

The frame number is the size and dimension of a gearbox mounting flange that specifically addresses the requirements of the application. Comparing the gearbox spec catalog according to the machine designer’s calculation to determine the appropriate frame size.
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Gear Ratio and Models

The gear ratio corresponds to the speed reduction and output torque needed by the application. It depends on how the machinery designer optimizes. The specifications of the planetary gearbox are determined according to the currently applied machinery and usage conditions.
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The backlash represents the precision of a planetary gear reducer, and it’s one of the important performance indicators of a planetary gearbox. It is also the main reason why the machinery designers choose the planetary gearboxes. The lowest backlash is not necessarily the best choice, the required backlash must be evaluated based on the components used in the actual application.
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Other factors

Some requirements such as where the gearboxes are used precisely. In certain applications, the gearboxes may be exposed to high temperature, high humidity, dust or low-temperature environment, limited space available for installation, etc. Some special requirements are corrosion resistance, special dimensions, ultra-high rigidity, and stiffness, etc.
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Hot Planetary Gearbox

Planetary gearboxes are divided into three main types according to their performance, including output shaft type, flange type, and right angle type.


Lubricants in planetary gearboxes

Even with how precisely the planetary gearbox is manufactured and assembled, there are constantly rolling or sliding surfaces inside. Each gearbox contains a lubricant – whether oil, grease, or a synthetic gel – to ensure the gears function well and prevent wear. In addition, the fat often also provides cooling and reduces noise or vibration.

Application of planetary gearbox

Due to the features and advantages of planetary gearboxes are often used when space and weight are limited, but a high reduction ratio and high output torque are needed.


In a robot to increase the torque.


In a printing press to reduce the speed of the rollers.


For precise positioning.


In a packaging machine for a reproducible products.

Types of Planetary Gearbox

“The input shaft (sun gear) and output shaft (planetary arm carrier) are parallel configured. The output shafts are available with some options like key shaft, smooth shaft or spline shaft, on which belt pulleys, gears and sprockets, etc. can be installed and mounted to machinery.”

Output shaft type

“The mounting flange of a planetary gearbox is designed according to ISO9409 specification. The flange type planetary gearboxes can be combined with various pinions and pulleys that provide high torque output in gears and racks applications.”

Flange type

“The mounting of the servo motor is rotated 90° by a right-angle housing, which saves space and makes the overall design of the equipment more compact.”

Right angle type

Frequently Asked Questions

Why is it Named a Planetary Gearbox?
The internal structure of the planetary gearbox is an epicyclic gear train (also known as a planetary gear set) mainly constructed of four major parts: a sun gear, planetary gears, a ring gear and a planetary arm carrier. In this gear train, the ring gear is fixed while the sun gear (input shaft) driven by the motor is located in the center. The sun gear is driven and moves the planetary gears which are fixed on the planetary arm carrier. Every planetary gear rotates on its own axis while revolves around the sun gear. The planetary arm carrier is the output shaft of the gearbox that transmits the power of the motor when planetary gears rotate and orbit. The operation of such gear set looks similar to our planetary solar system and that is how it is named, a planetary gearbox.
How Does a Planetary Gearbox Work?
In planetary gearboxes, maximum teethes of the gears rotate simultaneously. This motion delivers the high-speed deceleration, which obtains via relatively small gears and the low inertia reflected by the system. The teethes of the gears distribute the load and enable planetary components to deliver high torque. These gearboxes are most commonly used in airplanes, motorcycles, cars, and other vehicles. The grouping of high torque transmission, compact size, and speed reduction makes the planetary gearbox the best choice for applications where space is limited.
How do Planetary Gears Work?
Planetary gears can rotate around their axis and under the axes of sun and ring gears. Planet gears are constantly meshing with sun gears and ring gears to transmit torque.
What is a Planetary Gear Set?

A simple planetary gear set is constructed of three basic parts:

  • The sun gear is located in the center (central part)
  • Several planet gears
  • The ring gear (outer component)

The three parts devise a stage across a planetary gearbox. We can offer double or triple stages for greater ratios. Planetary gearboxes can be energized by either hydraulic motors, electric motors or diesel or petrol combustion engines. 

How to Choose a Planetary Gearbox?

The choice of a good planetary gearbox is very hard. Follow the below-given tips to choose the best planetary gearbox.

  1. Features required: First of all, you need to consider the ratio, backlash, torque, etc., to select your gearbox.
  2. Space: Multiple sizes of planetary gearboxes are available in the market. If you have low space, select a gearbox that has a small size so that you can install it easily.
  3. Environment: In some environments, moisture, dirt, or dust; may cause corrosion of the gearbox. Therefore, you must consider this factor for the selection of the gearbox and choose a gearbox that has a corrosion-resistant body.
What are the Drawbacks of Using a Planetary Gearbox?
Planetary gearboxes have many advantages and disadvantages. These gearboxes have complex modeling and manufacturing, making them more expansive than other types of gearboxes.

The planetary gearbox requires very precise construction. If one planet gear is closer to the sun gear than others, it can lead to the imbalance of the planet gear, which can lead to increased wear and failure. Furthermore, the compact size of the planetary gear ensures a high level of heat dissipation, which may require cooling in applications that operate very quickly or have continuous power.

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Our continuous R&D and experience of more than two decades have enabled us to Cater the growing needs and requirements of various industrial applications by offering a wide series of modular design planetary gearboxes, with different Mountings (foot, flange, shaft) and different input and output configurations (Solid, Hollow, Splined, shrink disc etc.). High flexibility and customization to suit various mountings for particular applications, high efficiency, high torque to weight ratio (compact) and wide range of gear ratios have helped us to carve out our name as “Prominent Manufacturers of planetary gearboxes”.


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