What is the selection criteria for choosing a gear reducer?

Posted on Aug 7, 2020

What is the selection criteria for choosing a gear reducer?

The gear reducer is used to adapt the characteristics (torque and speed) of the input and output axes of the mechanism. Therefore, you need to know the torque and speed of rotation.

Therefore, the first thing to ask yourself is the torque. The reducer increases the torque of the motor and thus allows the pick-up member to rotate under the influence of the new torque. Gear unit manufacturers sometimes indicate the minimum and maximum torque (expressed in Newton meters, N.m) that each of their products can handle. The torque density varies with the gear reducer. For example, planetary gears have a high torque density.

Another purpose of the gear reducer is to reduce the engine speed and we recommend taking into account the ideal gear ratio for your application. Based on the engine speed, the reduction factor is used to determine the output speed of the engine. This information is also indicated by manufacturers on the pages of their products. It is given in revolutions per minute.

Finally, you should ask yourself what type of reducer assembly is most suitable for your application. The input and output shafts of the gear reducer can be coaxial, parallel or orthogonal. It depends on the intended use.


What are the types of gear reducers?

There are four main types of reducers: planetary gears, worm gears, spur gears, and bevel gear reducers. Each reducer has its advantages and disadvantages. You will need to choose the one that best suits your intended use.

For example, if you are looking for a good level of performance, perhaps you should consider a planetary gear instead of a bevel gear.


The main types of gear reducers:

• planetary gearboxes

• worm gear reducers

• gear train gear reducers

• bevel gear reducers

• When should you use a planetary gearbox?

• Wittenstein planetary gearbox

• Wittenstein planetary gearbox


One of the main features of the planetary gear is coaxial assembly. This type of mounting means that the planetary gears are compact.

The advantages of planetary gear units are their compact size, high efficiency, low ground clearance and high torque-to-weight ratio. On the other hand, their complex and expensive construction requires specialist maintenance.

We recommend planetary gears for high acceleration applications (robotics) as well as for low speed but high torque applications (industrial rotary kilns). They are also widely used in machining centers and other machine tools as well as mobile machines used in public and agricultural works.


Main advantages

• up to 50% more torque than planetary gearboxes with equivalent spur gears

• better load distribution, which increases service life

• quieter operation

• low backlash not exceeding 2 arc-minute of play


When should you use a worm gear reducer?

Worm gear units have perpendicular input and output shafts. They are generally used for applications requiring very high gear ratios.

The mechanism of worm reducers is irreversible. This means that the snail cannot drive the worm. The advantage of this irreversible mechanism is that it provides a higher level of system security.

Worm gears are cheaper than planetary gears and are also quieter. Worm reducers do not vibrate, therefore they generate little noise and are more comfortable to use.

However, like planetary gears, worm gear units heat up quickly due to their compactness. They also have varying levels of performance. However, you can improve performance by combining the worm reducer with other gearboxes and transmissions.

We recommend that you choose this type of technology for conveyors, winches and handling.

:: Read more : How to Select a Gear reducer Box


When should a gear reducer be used?

Parallel axes gear reducers are typically used in high power applications such as conveyors

The simplicity of their technology will allow you to save on maintenance costs. Additionally, the gear reducers have a very high level of efficiency, close to 1.

They have a low reduction ratio per gear.


When should a bevel gear be used?

The main feature of bevel gear reducers is their angled bell crank which allows the user to change the machine's rotation system. This will allow you to switch from the lateral rotation system to the longitudinal rotation system.

Bevel gears are compact. They are also sturdy and can handle high power. Therefore, if you need high torque, we recommend choosing this technology. The solidity of their teeth allows them to be used with three-phase asynchronous or synchronous motors or asynchronous servomotors.

Bevel gears are quiet, which makes their use pleasant. Additionally, they offer a high level of performance and are energy efficient. However, their efficiency level remains lower than that of planetary gears. Bevel gears are also very expensive and require difficult maintenance.

Bevel gears are typically used in high-power conveyors, but also in mobile machinery used in agriculture or public works.


How to calculate the dimensions of your gear reducer?

To calculate the dimensions of the reducer, you need to select the correct shaft. There are three different shaft orientations: orthogonal, coaxial, and parallel.

If the gear unit has a perpendicular shaft orientation, the input and output shafts are perpendicular. This is often the case with bevel gear units and worm gears. Orthogonal shaft orientation is also used in industrial installations and differential bridges in cars.

If the gearbox has a coaxial shaft orientation, the input and output shafts are aligned. This is the case, for example, with planetary gearboxes or reducers used in engines and turboprop engines used in the aviation industry.

If the reducer has a parallel shaft orientation, the input and output shafts are parallel.


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