What is the selection criteria for choosing a gear reducer?

Posted on Aug 7, 2020

Gear Reducers

The gear reducers increase the torque of a motor and thus allow the pick-up member to rotate under the influence of the new torque. 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.

What Are Gear Reducers?

The gear reducers are used to adapt the characteristics (torque and speed) of the input and output axes of a mechanism, usually a motor or an engine. Torque describes the force translated from a linear axis to a rotational one. By changing the force/speed output, the operation of a machine can be precisely controlled and better results attained.

A Brief on Torque and Speed

The gear reducers increase the torque of a motor and thus allow 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, Nm) 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.

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

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 planetary gear instead of bevel gear.

The Main Types of Gear Reducers

• planetary gearboxes
• worm gear reducers
• bevel gear reducers

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

When Should You Use a Planetary Gearbox?

One of the main features of planetary gears is the coaxial assembly. This type of mounting reduces the setup of such a gear unit to a significant extent. Besides the compact size, the other advantages of planetary gear units are high efficiency, low ground clearance, and high torque-to-weight ratio. On the other hand, their complex and expensive construction require specialized 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.

What Is good about Spur Gears?

Gear reducers featuring a spur gear set are considered the most common type and are suitable for general applications. The tooth traces of the spur gears are straight and each trace is parallel to the rotational axis. The simplicity of its design makes it easy and cost-effective to manufacture, which is why the spur gear reducers are preferable across industries.

The main advantage of a spur gear reducer set is that it provides up to 50% more torque than planetary gearboxes with equivalent spur gears. The torque and speed transmission is straightforward and therefore efficient, which makes the unit ideal for high-speed applications, usually increasing speed. However, the straight gear traces inevitably cause louder noises when the gears shift and engage.

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. You can improve the performance by combining the worm reducer with other gearboxes and transmissions. Worm gear reducers are ideal for conveyors, winches, and handling.

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 and sturdy. Such a unit 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, 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 a 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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