Planetary Gearboxes
The Planetary Gearbox product lines offer the precision required, at prices that make them an affordable choice! Planetary Gearbox products are available in sizes from 40 mm to 120mm, which is ideal for motors ranging from NEMA 17 to larger than NEMA 42. The Planetary Gearbox is built with the design goal of offering a cost-effective product without sacrificing quality. Prices appear on this web site, with all the information required to select the perfect Planetary Gearbox product for your application.
Spur Gearboxes
The Spur Gearbox product lines offer the precision required, at prices that make them an affordable choice! Spur Gearbox products are available in sizes from 60 mm to 90mm.The Spur Gearbox is built with the design goal of offering a cost-effective product without sacrificing quality. We have a wide range of ratios to fit your application. Prices appear on this web site, with all the information required to select the perfect Planetary Gearbox product for your application.
  • What is a Planetary Gearbox?
  • How Much do Planetary Gearboxes Cost?
  • How Does a Planetary Gearbox Work?
  • Planetary Gearbox Advantages
  • Planetary Gearbox Selection

A Planetary Gearbox is a set of gears, shafts, and bearings that are enclosed in a housing and are arranged in a way that resemble a solar system, (thus the name planetary) with one or more planet gears orbiting around a sun gear. They convert input speed (typically provided by an electric motor) into a lower output speed while correspondingly creating higher torque. In other words, gear-boxes reduce RPM, turning it into power for use in low-RPM high-torque applications. Gearboxes come in different arrangements including planetary, bevel, cycloid, helical, harmonic, spur, and worm. Our focus here is on the planetary type of gear system.
Planetary gearboxes come in many sizes and torque capacities, and vary in speed ratios depending upon configuration. The gearboxes pictured to the right are approximately 60 mm to 2.4 inches in size, and produce output torque ranging roughly from 2,000 to 36,000 ounces per square inch.

Much larger planetary gearboxes exist for industrial processes, providing output torque in excess of 6,000,000 pounds per square inch. The focus of this website, however, is on these smaller planetary gearboxes.

The input power to these small planetary gearboxes comes from small electric motors (either a stepper motor, DC motor, or servo motor). Small motors are found in many household devices such as fans, clocks, timers, cassette players, printers, computer disc drives, etc.

The price of planetary gearboxes varies based on many factors. For backlash in the 30 arc-minute range, the cost for a gearbox might be as low as $100. For low backlash gearboxes under 5 arc-minutes they will cost quite a bit more. Below is a listing of planetary gearboxes products offered by Anaheim Automation - they list comprehensive specs and prices on their website with web discounts.

Model Cost Size Backlash  Ratio Range
gear motor $30.00 under 40 mm varies 3 to 512
GBPH-060 $195.00 60 mm square (Fits NEMA 23) 10 arc-min 3 to 512
GBPH-090 $295.00 90 mm square (Fits NEMA 34) 8 arc-min 3 to 1000
GBPN-120 $457.00 120 mm square (Fits NEMA 42) 9 arc-min 3 to 512


The planetary system has 3 main components: a central sun gear, a planet carrier (carrying one or more planet gears),and an annulus (an outer ring). The central sun gear is orbited by planet gears (of the same size) that are mounted to the planet carrier. The planet gears are meshed with the sun gear. An outer ring (the annulus) has teeth facing inward that also mesh with the planet gears.

The planetary gearbox is driven with the help of a center shaft, connected to a carrier plate carrying the three smaller gear wheels. These gear wheels run inside a toothed outer ring and drive the central gear cut around the central output shaft. This leads to the load being divided among many contact points around each gear, thus ensuring less friction and finally an increased efficiency on the planetary gearbox. The planet wheels in these gearboxes are generally set 120 degrees apart, leading to 'load equilibrium' and thus resulting in a balanced or 'zero force' within the geared components. The effect on the planetary gearbox results in very low wear and high shock loading capacity.

There are several configurations for planetary systems. Typical configurations require that out of the 3 components: one is the input, one is the output, and one is stationary.

For example, one configuration is where the sun gear is the input , the annulus is the output, and the planet carrier is stationary. In this configuration, the input shaft rotates the sun gear. The planet gears rotate on their own axes, simultaneously applying a torque to the rotating planet carrier, that in turn applies torque to the output shaft (which in this case is the annulus).

The rate at which the gears rotate (gear ratio) is determined by the number of teeth in each gear. The torque (power output) is determined by both the number of teeth and by which component in the planetary system is stationary.

The planetary gearbox arrangement is an ingenious engineering design that offers many advantages over traditional gearbox arrangements. One advantage is its unique combination of both compactness and outstanding power transmission efficiencies. Typical efficiency losses in a planetary gearbox arrangement is only 3% per stage. This type of efficiency ensures that a high proportion of the energy being input into the gearbox is multiplied and transmitted into torque, rather than being wasted on mechanical losses inside the gearbox. This creates a higher torque to weight ratio on the planetary gearbox.

Another advantage of the planetary gearbox arrangement is load distribution. Because the load being transmitted is shared between multiple planets, torque capability is greatly increased. The more planets in the system, the greater load ability and the higher the torque density. In addition because of the load distribution and the multiple planets, another advantage the planetary gearbox has is its low backlash.

If you are trying to be space efficient, then the planetary gearbox also is compact in size and less weight compared to other gear boxes.

The planetary gearbox arrangement also creates greater stability (it's a balanced system) and increased rotational stiffness. Disadvantages to the planetary arrangement include design complexity and accessibility issues.

It's important to know certain performance specifications when selecting a Planetary Gearbox, such as: input speed (this determines the gear ratio), output speed, and output torque required.

The table below contains specifications and pricings of available Planetary Gearboxes from the high-quality, low-cost supplier: AnaheimAutomation.com. Anaheim Automation carries the only brand of planetary gearboxes that have honed gears. Honed gears have many benefits including reduced noise, higher input speeds, increased surface durability and load-ability, and improved gear efficiency. Gear honing requires the use of dedicated, specialized tools and machines for their production. Find out more about the benefits of honed gears in the Literature Links section below.

Click to Purchase Planetary Gearboxes or to get More Specification Details available from Anaheim Automation.

Gear Backlash    • Lost Motion    • Torsional Stiffness & Elasticity    • Gear Precision    • Gear Honing

Partner Links

Motion Control Products
Linear Motion can be created by the use of a linear guide, linear rails, and linear guide blocks.

AC Motor
Here is a site dedicated to providing educational material on AC Motor technologies.

if you would like to exchange links, please email links@planetarygearbox.net