Zhejiang Sankai Mechanical and Electrical Co., Ltd

Planetary Gearbox

What is Planetary Gearbox



A planetary gear is a type of epicyclic gear system comprised of spur gears. In planetary gearing (also known as epicyclic gearing), a center gear, called a sun gear, serves as the input and driver of the set. Three or more “driven” gears (referred to as planets) rotate around the sun gear within a planetary gearbox. Finally, the planets engage with a ring gear from the inside, which makes an internal spur gear design. Because the planet gears are evenly distributed around the sun gear, planetary gear trains are known to be extremely rugged designs.


Advantages of Planetary Gearbox

High efficiency: Planetary gearboxes provide high efficiency due to their design, resulting in less power loss and more energy savings.


Compact size: Planetary gearboxes are compact in size and offer high power density, making them ideal for applications where space is limited.


High torque capacity: Planetary gearboxes provide high torque capacity due to their design, making them suitable for heavy-duty industrial applications.


Quiet operation: Planetary gearboxes operate quietly due to the even distribution of forces and the use of multiple gears, reducing noise pollution in the workplace.


Flexibility: Planetary gearboxes offer flexibility in terms of speed and torque ratios, making them adaptable to various industrial applications.


Long service life: Due to their robust design and high-quality materials, planetary gearboxes have a long service life, resulting in reduced maintenance costs and downtime.


Why Choose US



Our Factory
Zhejiang Sankai Machine and Electric Co.,Ltd is an integrative and professional manufacturer of power transmission device, which specialize in scientific research, production and marketing.


Adopting advanced detecting equipment and means, company establishes a quality control system that is in accordance with 1S0900 I: 2015. Products are sold all over the country, exporting to Southeast Asia, Europe, America and other regions. Sankai will continue, as we always do, to strive to become a leader of power transmission industry.


Our Products
Our company specialize in High Precision Planetary Gearbox, NMRV series Worm Gearbox, UDL series Stepless Speed Variator, SRC series Helical Gearbox, SKM series Helical-Hypoid Gearbox, Precision Gearbox for Robot Arm and PC Helical Gear Unit.


Quality services
Sincerely Sankai determine to provide service of better quality, in-time and fast reply to our clients. And Sankai is looking forward to cooperating with domestic and foreign friends and grow together with our hard work and professionalism.


Types of Planetary Gearbox

Multi-stage planetary gearbox
A multi-stage planetary gearbox is a type of gearbox that uses multiple sets of planetary gears. To achieve a desired output speed or torque. Unlike a single-stage planetary gearbox. Which has only one set of gears. Multi-stage has two or more sets of gears arranged in series to achieve higher gear ratios.


In-line planetary gearbox
An in-line planetary gearbox is a types of planetary gearboxes . Where the input and output shafts arranged in a straight line. The gearbox consists of a central sun gear, several planet gears, and an outer ring gear. The planet gears mounted on a carrier and rotate around the central sun gear. While also rotating around their own axis.

Offset planetary gearbox

An offset planetary gearbox, also known as a parallel shaft planetary gearbox. That is a type of planetary gearbox where the input and output shafts arranged in an offset or parallel configuration. The gearbox consists of a central sun gear, several planet gears, and an outer ring gear. The planet gears mounted on a carrier and rotate around the central sun gear. While also rotating around their own axis.

Coaxial planetary gearbox

A coaxial planetary gearbox, also known as an inline planetary gearbox. That is a form of planetary gearbox in which the input and output shafts are coaxially arranged, i.e. on the same axis. A center sun gear, several planet gears. And an outer ring gear comprise the gearbox. The planet gears mounted on a carrier and revolve around the central sun gear as well as their own axis.

Right angle planetary gearbox

A right angle planetary gearbox is a type of planetary gearbox. where the input and output shafts arranged at a 90-degree angle to each other. The gearbox consists of a central sun gear, several planet gears, and an outer ring gear. The planet gears mounted on a carrier and rotate around the central sun gear. while also rotating around their own axis.


The Steps of Choose a Planetary Gearbox for a Concrete Mixer

Select the reduction ratio
Input Speed/Output Speed can be used to compute the reduction ratio. If the output torque is unknown, the torque can be determined using the formula.


Calculate the output Torque(Nm)
Output torque = (P x 9546)/N
Where P is Power in kW (Multiply P with 0.746 if power is in HP)
N is output speed (RPM)


Find the service Factor
Assume the service factor depending on the type of application and working hours. The Top Gear catalogue mentions it.


Calculate the Rated Torque
Rated torque = Calculated output torque * service factor.


From the Catalogue, choose a Model
Determine the Gearbox's life based on operating hours and output speed (n2h)
Select the most appropriate model based on rated torque and lifespan.


Check the thermal rating
The continuous power transmitted by a gear unit with splash lubrication and a maximum oil temperature of 90° C at an ambient temperature of 25° and an input speed of 1440 RPM is referred to as the thermal rating.
Following the model selection, the thermal capacity of the reducer thermal rating must be checked (Kw)


Verification of hollow frame
If the selected planetary gearbox is required in a hollow input arrangement, the frame size must be confirmed. Check to see if the frame size for a certain model is appropriate for the motor's rated power.


Check for Overhang Load
When the output is coupled to a sprocket, pulley, timing belt, gear, or friction wheel, radial load is generated on the shaft. Which must be examined for overhang load capability at high and low speeds.


How to Choose Planetary Gearbox
Precision Servo Gearboxes
Precision Servo Gearboxes
Coaxial Gearbox
Precision Servo Gearboxes

High Torque Output:
Planetary gear systems are capable of providing high torque output relative to their size. This makes them suitable for industrial applications. where substantial force or power need required.


Compact Design:
The arrangement of gears in a planetary gearbox allows for a compact and space-efficient design. This is crucial in industrial settings where space is often limited. and a smaller footprint is advantageous.


Efficiency in Power Transmission:
The multiple gear contacts in a planetary gear system contribute to high efficiency in power transmission. This efficiency is essential in industrial applications. where minimizing energy loss is a priority.


Planetary gearboxes are versatile and adapted to various industrial applications. They find use in a wide range of industries, including manufacturing, robotics, aerospace, and automotive.


Precise Speed Control:
The design of planetary gearboxes allows for precise speed control. This is particularly important in industrial machinery. where accurate and adjustable speed outputs required for optimal performance.


Low Backlash:
Planetary gear systems typically exhibit lower backlash compared to some other gearbox types. Lower backlash ensures more precise and responsive motion control. a critical factor in industrial applications.


Durability and Longevity:
The distributed load among multiple gears in a planetary gearbox. contributes to enhanced durability and longevity. This makes them reliable for continuous operation in demanding industrial environments.


Customization Options:
Manufacturers often offer customization options for planetary gearboxes. This flexibility allows industrial users to specify gear ratios, sizes, and other parameters. to tailor the gearbox to their specific application requirements.


Handling Radial and Axial Loads:
Planetary gearboxes can effectively handle both radial and axial loads. making them suitable for applications where there are varying load conditions.


Ease of Maintenance:
The modular design of planetary gearboxes simplifies maintenance and repair. Individual components replaced or serviced without disassembling the entire gearbox, reducing downtime.


Precision Servo Gearboxes


Why Are Planetary Gears Used

Planetary gearing is used in challenging applications because the three planet gears are evenly distributed around the sun. They are more durable and power dense, allowing them to handle higher torques and reductions in a smaller, more compact package. Because of Planetgear’s unique self-aligning properties, they can also withstand higher shock loads and overhung loads. Double Row Full Complement Cylindrical Roller Bearing for Planetary gears Full complement cylindrical roller bearings with no outer ring are commonly used in planetary reducer gears. Reducers are essential devices used by a variety of machinery and equipment. To rotate and achieve long life, the bearings must meet the requirements of high speed and stability under various working conditions. Full complement cylindrical roller bearings without an outer ring, which use the inner hole of the gear as the outer ring and outer raceway of the bearing to simplify the host design and save space. The complete roller design can achieve the maximum rated load in a small area, and the average increase in effective load should be between 15% and 20%.

Planetary Gearbox Application



Conveyor Systems:
Planetary gearboxes employed in conveyor systems to control the speed and torque of conveyor belts. facilitating smooth material handling in industries such as manufacturing and logistics.


Mixers and Agitators:
In the construction and chemical industries, planetary gearboxes used in mixers and agitators. to efficiently blend and process materials.


Automotive Transmissions:
Planetary gear systems are a crucial component in automatic transmissions of vehicles. providing efficient torque conversion and enabling smooth gear shifting.


Robotic Systems:
Industrial robots use planetary gearboxes in their joints. and actuators for precise and controlled movement. making them essential in manufacturing and assembly processes.


Aerospace Applications:
In aerospace, planetary gearboxes used in various applications. including aircraft landing gear systems, where their lightweight and compact design are advantageous.


Wind Turbines:
The gearboxes in wind turbines use planetary configurations. to increase the rotational speed of the low-speed shaft. optimizing energy conversion for electricity generation.


Mining Equipment:
Heavy-duty mining equipment, such as crushers and conveyors. utilizes planetary gearboxes for reliable and efficient power transmission in demanding environments.


Printing and Packaging Machinery:
Planetary gearboxes used in printing and packaging machines to control the speed and torque of rollers. ensuring precise and consistent printing and packaging processes.


Textile Machinery:
In textile manufacturing, planetary gearboxes employed in spinning. and weaving machines for efficient control of the production process.


Steel Mills:
Rolling mills in steel production use planetary gearboxes. to achieve precise control over the rolling process, ensuring quality and consistency.


Renewable Energy Systems:
Planetary gearboxes used in solar tracking systems. to adjust the orientation of solar panels for optimal exposure to sunlight.


Marine Applications:
In marine propulsion systems, planetary gearboxes utilized to control the speed and torque of ship engines. ensuring efficient power transmission.


Food Processing Equipment:
Industrial planetary gearboxes find applications in food processing equipment. such as mixers and conveyors, providing precise control over the processing stages.


Industrial Pumps:
In pumps used for fluid transfer in various industrial processes. planetary gearboxes employed for speed control and torque management.



Working Principle of Planetary Gearbox

● Planetary gearbox includes a central sun gear, an outer ring, a carrier, and the planetary gears.
● Planetary gears are proportional to the ring part, which is fixed, causing the planetary parts to rotate around the sun gear. Input power to the sun gear creates spinning
● Carrier keeps the planetary gears in their basic form and sets their gaps. It turns with the planetary parts and incorporates the output shaft.
● Planetary gears are employed in gearboxes that energize everything from basic plant devices to cutting-edge electric systems.
● Having several teeth to share the load also permits planetary parts to transfer high levels of torque.
● Combination of large speed reduction, compact size, and high torque transmission makes planetary gearboxes a common option for space-constrained usages.

Precision Servo Gearboxes
Precision Servo Gearboxes


Construction of Planetary Gearbox

Sun Gear: Sun gear is located at the center of the assembly and meshes with the teeth of the planet gears. It receives the input for the gear set and is known as the main gear in a planetary gear set.


Planet Gear: Planet gear runs with the motion of the sun gear. Planetary gears have one or more planet gears and control the speed of the transmission of power.


Ring Gear: The outer ring of a planetary gear system is known as the ring gear. It contains teeth on its internal circumference and is smooth on its outside edge.


Carrier: The carrier is portable and rotates with respect to the sun gear. It is associated to the centers of each of the planet gears to give support. The carrier has a shaft for each of the planet gears that surround the sun gear and are surrounded by the ring gear.


Spur or Helical Gear: Construction of a planetary gear set can include spur or helical gears. The difference between the two gears is their helix angle, with spur gears having a zero-helix angle while helical gears have a helix angle of 10 to 30 degrees.


How to Maintain Your Planetary Gearbox


Maintaining planetary gearboxes is crucial to ensure their optimal performance and longevity. Here are some best ways to maintain planetary gearboxes:


Regular inspections
Inspect the gearbox regularly for signs of wear and tear, such as vibration, noise, and leaks. This can help identify any potential issues before they become significant problems.


Proper lubrication is critical to the smooth operation of a planetary gearbox. Ensure that the gearbox is adequately lubricated with the recommended oil or grease and that the oil level is maintained within the recommended range.


Temperature Control
Planetary gearboxes can generate a lot of heat during operation. Overheating can cause the lubricant to break down and result in premature wear and tear. Ensure the gearbox is adequately cooled, and the temperature is maintained within the recommended range.


Proper Installation
Ensure the gearbox is installed correctly and all connections are tight and secure. Proper alignment and load distribution can help reduce stress on the gearbox and increase its lifespan.


Regularly clean the gearbox to remove dirt and debris that can clog vents or damage the gearbox's components.
Proper maintenance of planetary gearboxes is essential to ensure their optimal performance and longevity and prevent costly repairs or replacements.



Q: What does a planetary gearbox do?

A: How are Planetary Gears used? Generally, planetary gears are used as speed reducers. They are used to slow down motors and increase the torque. Torque is the working power of the machine.

Q: What are the gearbox types planetary?

A: We offer a broad range of gear manufacturing capabilities, including the capacity to manufacture all of the individual gears that comprise a planetary gear system. Planetary gearboxes are classified into three types: wheel drive, shaft output, and spindle output.

Q: How does a planetary gear motor work?

A: The principle of a DC gear motor is that the first portion of it transforms some energy into mechanical energy, and the second portion is made to transmit the remaining mechanical energy to the output shaft to modify its speed.

Q: What is the difference between a planetary gear and a bearing?

A: Planetary transmissions could be simpler, cheaper, and more rigid. Gear bearings are conceptual mechanical components so named because they function as gears and as roller and/or thrust bearings. Gear bearings will be essential components of the next generation of compact, large-mechanical- advantage gear drives.

Q: Why do we need planetary gears?

A: Planetary gears – Function and construction. The task of gears is to transmit torques and to change the speed of rotation or the torque between the input and the output. When it is necessary to increase torque, planetary gears are often employed, particularly in the automobile industry.

Q: Is planetary gearbox self locking?

A: Planetary gearheads with 4-5 stages are typically rated as "functionally self-locking" within the permissible torque level unless there is some special back-drivable design present. A spur gearhead is always back-drivable. Even with more than 3 stages.

Q: What is the difference between a gearbox and a planetary gearbox?

A: Compared to traditional industrial gears, planetary gearboxes are more light-weighted. The torque transmitting capacity can be increased by adding the number of planet gears. It can use multiple gears to share the load for high power density and transmission efficiency.

Q: How efficient is a planetary gearbox?

A: Planetary gearboxes also have a high torque transmitting capacity due to the distribution of the load across several planets, making them stable and long-lasting. They are also highly efficient, with low power losses and transmission efficiency up to 98% for the first stage of the gearbox.

Q: Are planetary gears stronger?

A: Planetary gearboxes are often considered stronger than spur gearboxes due to their design and construction. Here are a few reasons why planetary gearboxes are typically stronger: Increased torque capacity: Planetary gearboxes are able to transmit more torque than spur gearboxes due to their multiple contact points.

Q: Do all automatics use planetary gears?

A: Most automobiles use a form of automatic transmission called a hydraulic planetary automatic transmission, which is also used in a scaled-up version in some industrial and commercial equipment and heavy-duty vehicles.

Q: How do planetary gears differ from other gears?

A: Planetary gear trains provide high power density in comparison to standard parallel axis gear trains. They provide a reduction in volume, multiple kinematic combinations, purely torsional reactions, and coaxial shafting.

Q: Do cars use planetary gears?

A: They are often used as the key components in the hydraulic planetary automatic transmission, the most frequently used type of automatic transmission. In fact, they're found in most of the automatic transmissions that modern cars are equipped with today.

Q: How many gears does a planetary gearbox have?

A: Basic planetary gearing consists of three sets of gears, each with different degrees of freedom. Planet gears rotate around axes that revolve around a sun gear which spins in place. A fixed ring gear holds the planet gears in orbit about the sun gear and meshes with both the ring and sun gears.

Q: Why are planetary gears stronger?

A: Since the internal sun gear meshes with multiple outer gears at once, planetary gear motors are able to sustain higher loads. The ability to distribute the load over multiple contact points makes planetary gear motors optimal for high torque, high RPM applications like industrial machinery.

Q: Does CVT use planetary gears?

A: Unlike other transmission types that use solid gears in one form or another to effect fixed gear ratios, CVT transmissions do not use any gears, except for a set of planetary gears and a couple of clutch packs to facilitate a reverse function.

Q: Where can I use a planetary gearbox?

A: Planetary gear transmission (PGT) is widely used in the automobiles, helicopters and marine applications. PGT is more advanced than counter-shaft drive because of its higher torque-to-weight ratio, compactness and reduced noise.

Q: What is the life expectancy of a planetary gearbox?

A: Theoretical gearing lifetime is 20,000h if your rated torque is t2n. Acceleration torque can be used 2,000 hours if it is under tmax.

Q: Can you backdrive a planetary gearbox?

A: Yes, Micron planetary gearheads are fully backdriveable. The backdrive torque is dependant on gearhead size, style, and ratio, and will vary.

Q: Are planetary gearboxes expensive?

A: Generally, planetary gearboxes are considered to be more expensive than other types of gearboxes due to their complex design and manufacturing process.

Q: Are planetary gears noisy?

A: Meshing of the gears in the planetary gear set that forms the ratio-changing mechanism of an automatic transmission produces gear noise over a wide range of driving conditions from low to high vehicle speeds. However, such gear noise often becomes a problem in the relatively low load region.

As one of the most professional planetary gearbox manufacturers and suppliers in China, we're featured by quality products and competitive price. Please rest assured to buy planetary gearbox for sale here from our factory. Contact us for quotation and free sample.

High Precision Planetary Gearboxes, Variator, Compact Planetary Gearbox