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Oct 18, 2016 - The Differences Between Planetary and Spur Gear Motors

For industrial use, the two most common kinds of gear motors are planetary gear motors and spur gear motors. Choosing the right type of motor is important to ensure maximum efficiency in your application; if you're not familiar with these types of motors, it can be frustrating trying to pick the right one.

If you’re looking for top quality planetary gear motors, take a look at our options from Bonfiglioli today. Gordon Russell sells other Bonfiglioli products from our location in BC.  Keep reading for a quick overview of both, and the differences between them, and make your decision process easier.  

What are Planetary and Spur Gear Motors?

Planetary Gear Motor: A planetary gear motor shares the torsional load over several planet gears, so it works well when a higher torque is required. Torque is a twisting force that causes rotation in objects, or in this case, gears. In terms of solid mechanics, torsion is the twisting of an object due to an applied torque. More torque is often needed in automobiles or railcar movers, where there are multiple gears working at the same time.

A planetary gear motor mimics a planetary rotation system; the input shaft drives the central gear, also known as the sun gear, which then turns the surrounding  gears, also known as planet gears.

This system lets each of the planet gears to deliver enough torque in perfect synchronization with each other, which takes the pressure off of each individual gear, resulting in lower chances of the machine breaking down, and also leads to greater output capacity.

Spur Gear Motor: A spur gear motor is simpler in design and tends to be less expensive than a planetary gear motor. Spur gear motors work better for lower torque applications.  Torque is limited in spur motor gears since each gear bears the whole load.

Differences And Similarities

Both planetary and spur motor gears are made from different kinds of metals; these include steel, nickel-steel, and brass. Some planetary gear motors use plastic, though this isn’t seen often. Most experts will agree that steel cut gears are the most durable; this makes them much more ideal for applications that require more torque. Nickel-steel gears, on the other hand, tend to be more absorptive and are better at holding lubricant than other materials.

Lubrication is important no matter what material the gear is made of, and is especially essential when the machine is working at high speeds or has heavy loads. Planetary gears are better than spur gears when it comes to retaining lubrication. This is due to the planet gears being able to recapture any oil that gets removed from the sun gear. This also helps the planet gears operate at faster speeds. Spur gear motors work better at lower speeds because the oil tends to fly off the gears. The inadequate lubrication makes working at higher speed more difficult for spur gears, as they will to burn out faster.

Planetary Gear Motors are cylindrical in shape, and come in many power levels and sizes. Planetary gear motors are usually made of steel or brass, and sometimes plastic. This type of motor has several gears and teeth sharing the work, so there is less worry about wear and stress, which makes it easier to attain large amounts of power transfer without harming the gears. Planetary gear motors are also more expensive to produce because they require more parts. This includes the sun gear, an outer gear, several planet gears, and a moveable arm to hold the planet gears. While this system results in higher efficiency and lower gear noise, it is also more complex and parts can be hard to get to or inaccessible, making repairs difficult.

Spur gear motors are commonly made from either brass or steel. Spur gear motors are most often cylindrical in shape, and the gears can be noisy, especially if there is not enough lubrication. The gears are straight-toothed and connect to parallel shafts, which delivers high torque at lower speeds. Important design factors for spur gears are the size of the gears and the number of teeth on each gears. The size and number of teeth will determine the gear ratios for output torque and the shaft speed. Inadequate lubrication can damage the teeth, which can lead to gear stress or slippage and even break the gear motor. Spur gear motors tend to be less expensive to produce than planetary gear motors, due to the fact that they use fewer gears and are much simpler to manufacture.

Looking for top quality and efficient gear motors? Check out the 300 - Planetary Gear Motor from Bonfiglioli today! Call us at (604) 940-1627 for inquiries in BC.