A Quick Guide to Planetary Gearbox

Posted on Feb 3, 2021

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Planetary Gearbox

With excellent speed control capability and relatively high torque output, the planetary gearboxes are a popular choice for machinists. Today, planetary gearboxes are widely used for medical, construction equipment as well as a broad range of metalworking production like automatic welding, vending, material handling machines and conveyor systems or food processing equipment such as automatic mixers, and many more.

What Is a Planetary Gearbox Used for?

A planetary gearbox is one type of gear reducer with the input and the output shafts aligned, reducing the input speed and providing the largest torque density in a compact configuration. The speed reducer which is widely utilized for electric motors is also called planetary gear reducer or inline planetary gearbox reducer. 

In addition to the planetary gearbox, there is a large range of other types of speed reducer. The most common ones are the gearbox form. The universal goals of these gear reducers are to primarily control and decrease the input speed of the motor and offer the precise, proper output speed through the speed reduction process. This output speed can determine the operational rate, effectiveness, and available jobs of the moving parts in the motorized machines. Second, with the gear mechanisms, the gearboxes multiply the torques to optimize the performance of the fixed mechanisms of the machines. With a planetary gearbox, the motor speed can be ideally controlled even when applied to applications with high rotational speed.
 

Construction of a Planetary Gearbox

The planetary gearbox reducer design basically consists of a central “sun gear”, an outer ring, the planetary gears, and also a carrier. The outer ring is also known as the internal gear since the gear teeth face inward. In this planet-wheel mechanism, the planetary gears mesh with the central sun gear. These planetary gears also mesh with the stationary ring. The arrangement allows the planetary gears, which are set the spacing and held by the carrier, to revolve around the sun gear at the center.

The input power rotates the sun gear, as a result, the planetary gears around also rotate on the axes. The carrier spins with the gears, incorporating the output shaft. The difference in the amount of the gear teeth among the working gears makes the output gear run slower, completing the speed reduction as well as providing ideal torque. The appropriate amount of the torque the planetary gearbox reducer should generate should be critically identified and calculated, and this also significantly affects whether the type of speed reducer is best suited for the application. In some complex motorized works, many physical factors should be aware of when calculating, for instance, friction, resistance, gravity, inertia, and many more. These factors should be accommodated and resisted by enough torque to ensure the equipment run smoothly. 

In the compact design of planetary gear reducers, the rolling and sliding surfaces of the moving components should be always lubricated by oil, grease, or synthetic gel. The gearbox reducer contains one of these lubricants to not only keep the gears from wear but also reduce the noise, vibration, and the risks for excessive heat, ensuring smooth function.
 

:: Read More: The Beauty of Planetary Gearbox For Servo Motor

Where Are Planetary Gearboxes Used?

With excellent speed control capability and relatively high torque output, the planetary gearboxes are a popular choice for machinists. Today, planetary gearboxes are widely used for medical, construction equipment as well as a broad range of metalworking production like automatic welding, vending, material handling machines and conveyor systems or food processing equipment such as automatic mixers, and many more. 

Planetary gearboxes are also commonly used in automatic transmission systems. For instance, using them to increase the torque in the robot, to reduce the speed of the rolls in a press, position the items precisely, and other 3D printing and modern transport applications. The ideal speed control ability of an electric motor which consistently supplies correct output speeds with minimal backlash makes the planetary gearbox becoming an essential investment for the motion control systems.
 

Advantages of Planetary Gearboxes

Planetary gearboxes are the ideal choice that typically meets all the designs of servo motor applications. The speed reducer has a much more compact construction when compared to other gear types, which offer longer lifespans and low maintenance requirements. Therefore, the type is ideal for space-constrained applications.

Also, the type of gear reducers provides great torque transmission with ideal stiffness but creates less noise in the operations. When it comes to torque density, planetary gearboxes are a popular choice for machinists since they have the highest nominal torque. Nominal torque refers to the maximum permissible consistent torque that may act on the output shaft in the system, which is defined by either the constant power of the motor or by the constant load of the gearbox system. 

In the planet-wheel design of planetary gearbox, many gear teeth are engaged at once, achieving such a high-performance speed reduction with relatively small and compact construction. Within the process, there is low inertia that is reflected back to the servo motor. These teeth mentioned here easily share the load, permitting the gear reducer to transport higher torque and supply large speed reduction for different servo applications.
 

Disadvantages of Planetary Gearboxes

The critical and precise manufacturing and assembly of the complex planetary gearbox design make the product a less economical speed reduction solution. The high precision production of this gear reducer is extremely vital to prevent any imbalance. For instance, mounting single planetary gear too close to the central sun gear than the other planetary gears, the imbalances happening in the arrangement may cause significant premature wear as well as operational failure.

Another drawback of using the planetary gearbox is heat dissipation. The compact design makes the planetary more challenging to dissipate the heat, therefore, a cooling element like lubricating oil is required especially when using for tasks that consistently work at a high speed.

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