DC Gear Motors: Planetary vs. Spur Gearheads

When it comes to DC Gear Motors, the two most popular options are Planetary and Spur gear motors. Learn which is the best fit for your next project.

Planetary and Spur gear motors are the two most common types of gear motors used in industrial applications. When trying to decide which gear motor is best suited for your application, there are a few key aspects to keep in mind. Both gear heads have their own unique advantages and disadvantages, based on the intended usage and requirements.


Planetary Gear Head Construction

The gears inside of a planetary gear head have a unique method of meshing together. They have an internal gear, called the sun gear. The sun gear drives multiple outer gears known as planetary/satellite gears. The planetary/satellite gears mesh with an outer ring to guide and hold them in place. The outer ring is fixed and incorporated in the motor housing. 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. Due to their versatility, planetary gear motors are also excellent choices for less demanding applications like articulating television mounts.

Spur Gear Head Construction

A spur gear head's construction consists of larger gears that mesh with smaller gears. The gears are mounted on parallel shafts but offset from one another. The meshing of the smaller gears with the larger gears reduces rpm transforming it into torque. The tooth pitch of the gears is critical in determining the final output speed and torque of the gear motor.

Adding multiple gear stages within the gear head produces larger reduction ratios resulting in even lower output speed and higher output torque. Spur gear-heads have a single contact point at any time. This means that any load is held entirely by a single point of contact between two gears.

A spur gear motor is a cost effective solution, suited for low torque and low rpm applications such as an automated paper towel dispenser.

Torque & Speed

The two main parameters that are commonly associated with gear motors are torque and speed. When it comes to torque and speed, a planetary gear motor is more effective in high speed, high torque applications. As mentioned above, the multiple contact points between the gears of a planetary gear-head are the reason for its effectiveness in these conditions.

The less complex construction of a spur gear head results in them not being able to hold as much of a load as their planetary counterpart. As the spur gear motor's speed increases, it will produce a fair amount of noise without the proper internal lubrication. The ability to add multiple stages and have high gear reduction ratios allows spur gear motors to handle higher loads if needed.

In planetary gear systems the gear lubrication tends to stay within the teeth of the gears whereas, with spur gear systems, the lubrication tends to disperse from the gears at higher speeds.

Applications

Planetary gear motors are most commonly used in robotic and industrial automation applications. They can be found in applications like label printing machines, articulating tv mounts, tactical robots, vinyl cutting machines, and laser measuring apparatuses. The high precision and efficiency of these motors ensure that all types of applications operate at the highest level.

Low speed applications that benefit from spur gear motors are automated paper towel dispensers, telescope positioning equipment and electro-mechanical door locks. Higher speed applications where spur gear motors are used include small appliances, such as blenders and food processors.

Choosing the Right Gear Motor for Your Application

Choosing the proper gear motor configuration depends on the specifications required and the given application.

Although spur gear motors work best in low speed, low torque situations, with the right reduction ratios, spur gear motors can be produced with more torque while still offering excellent efficiency. The simplicity and cost-effectiveness of spur gear motors are the main selling points.

Planetary gear motors are alternative solutions that are capable of handling heavier loads. In addition to their durability, planetary gear motors also provide a higher efficiency over spur gear motors.

Due to the construction of a planetary gear head, the length of a planetary gear motor is usually longer and narrower than spur gear motors. If you have certain size constraints within your application, please keep those in mind when deciding on your next gear motor.

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