A planetary gearbox, also known as an epicyclic gearbox, is a type of gear system that uses a central sun gear, multiple planet gears, and an outer ring gear to transmit torque and speed. The planet gears rotate around the sun gear and are mounted on a planet carrier, which can also rotate, creating multiple gear ratios within a compact design.
A typical planetary gearbox consists of three main components:
Sun Gear – The central gear connected to the input shaft.
Planet Gears – Multiple smaller gears that rotate around the sun gear.
Ring Gear – An outer gear with internal teeth that mesh with the planet gears.
Carrier – Holds the planet gears in position and transfers torque to the output shaft.
This configuration enables the gearbox to deliver high torque output, compact design, and excellent efficiency — all within a small package.
When the input shaft drives the sun gear, the planet gears rotate around it while simultaneously meshing with the ring gear. The carrier that holds the planet gears transfers this motion to the output shaft.
By fixing different components (ring, carrier, or sun), different speed and torque ratios can be achieved, allowing the same gearbox to serve various motion control applications.
High Torque Density: Multiple planet gears share the load, enabling compact yet powerful transmissions.
Efficiency: Up to 95–98% efficiency per stage.
Compact Size: Inline configuration saves space compared to traditional gearboxes.
Low Backlash: Ideal for servo systems and precision automation.
Durability: Uniform load distribution reduces wear and extends service life.
Planetary gearboxes are widely used in applications that require precise motion control and high torque within limited space, such as:
Robotics and automation systems
Electric vehicles and AGVs
CNC machinery and packaging equipment
Industrial conveyors and material handling systems
Wind turbines and renewable energy systems
At PJM Automation, we design and manufacture custom planetary gearboxes optimized for your specific needs.
Whether you require a high-torque gearbox for heavy-duty machinery, a low-backlash servo planetary gearbox, or a compact drive solution for robotics, our engineering team tailors each gearbox for precision, durability, and global compatibility.
Explore our Custom Planetary Gearbox Solutions to learn how we can enhance your motion control systems with reliable, high-performance planetary gear technology.
Planetary gears offer several key advantages that make them the preferred choice for high-performance motion control and power transmission systems. Their unique configuration provides superior strength, precision, and efficiency compared to conventional gear designs.
Planetary gears distribute load evenly among multiple planet gears, allowing the system to handle significantly higher torque without increasing the gearbox size. This design enables a compact yet powerful transmission — ideal for applications where space is limited but torque demand is high.
With continuous contact between the gears and balanced torque distribution, planetary gearboxes can achieve up to 98% efficiency per stage. This means less energy is lost during transmission, improving overall system performance and reducing heat generation.
Unlike traditional parallel shaft gearboxes, planetary gearboxes are inline — meaning the input and output shafts are on the same axis. This configuration minimizes installation space and supports integration into compact machines like robots, CNC systems, and automated equipment.
Planetary gears are designed for tight tolerances, minimizing backlash and ensuring precise motion control. This feature makes them ideal for servo motors, positioning systems, and other automation applications requiring accuracy and repeatability.
Because multiple planet gears share the load simultaneously, stress on individual gears is significantly reduced. This uniform load distribution enhances durability, shock resistance, and service life, even under heavy or fluctuating loads.
By fixing different components (the sun, carrier, or ring gear), planetary gearboxes can provide a wide range of speed reduction ratios and torque outputs. This flexibility allows engineers to customize planetary gearboxes for various industrial applications — from electric vehicles to wind turbines and industrial automation.
The symmetrical design and multiple points of gear contact contribute to smooth, quiet operation, minimizing vibration and noise. This is especially important for medical devices, robotics, and precision instruments.
Thanks to their robust design and efficient torque transmission, planetary gear systems offer long operational life with minimal maintenance requirements — making them a cost-effective and reliable solution for continuous-duty applications.
In summary, planetary gears combine power density, precision, and reliability in a compact form. These benefits make them indispensable in modern industries that demand efficient and high-performance mechanical drives.
If you’re looking for a custom planetary gearbox engineered to match your exact requirements, explore PJM Automation’s tailored gearbox solutions — designed to deliver maximum torque, accuracy, and efficiency for your system.
