Cycloidal gears or wave gears: when is which the better choice?

Cycloidal gears and wave gears: two precision gears, two design concepts, two solutions tailored to various requirements. That's why they complement each other perfectly and together create the perfect team in the field of automation. We explain the key differences, highlight their strengths and provide an overview of the most important features.

Both technologies meet the highest standards for precision, torque and torque density, making them ideal for applications where maximum accuracy is required. While cycloidal gears, thanks to their exceptional stiffness, specialize in transmitting higher torques, backlash-free wave gears perform primarily in the lower torque range and are used wherever high efficiency is required and the available installation space is limited.

Size is not always the deciding factor

In most cases, geometric size is the decisive criterion for or against choosing one of these two technologies. However, there is an area where both gear types can be used - namely for external diameters from 100 to 150 mm and/or torques from 250 to 450 Nm. Which technology is the better choice depends largely on the requirements of the specific application. When high torques are in the foreground, precision cycloidal gears show their advantages. If the most important thing is the lack of backlash, wave gears (developed and manufactured at the Ovalo GmbH plant in Limburg am Lahn) have the advantage.

The most important features at a glance:

Principle of operation

In cycloidal gears, power is transmitted via cam discs and rollers. In wave gears, this function is performed by a cylindrical, elastically deformable steel element with external teeth, known as the flexspline. The appropriate operating principle is the basis for the characteristic properties of both technologies.

Torque

Our wave gears provide torques ranging from 4.5 to 382 Nm. This torque range is largely due to the use of the flexspline as a flexible transmission element and the elliptical deformation of the generator shaft bearing, as both of these would lead to significantly greater mechanical stress and therefore reduced service life at very high torques. Our cycloidal gears cover a torque range up to 70,000 Nm. The almost complete contact and even distribution of forces in the gearbox ensure high stiffness, thus enabling the transmission of very high torques.

Precision / Looseness

Gear accuracy depends largely on backlash and hysteresis losses. The lower the value, the more precise the gear works. The wave gears are completely backlash-free, which means the backlash is zero. Our cycloidal gears feature reduced or virtually zero backlash of just 0.1-0.2 arcminutes. Hysteresis losses for both technologies are a maximum of 1 arcminute. For comparison: conventional reduced backlash planetary gears typically have a backlash of around 3 arc minutes, while standard planetary gears can have as much as 7 arc minutes.

Moment stiffness

Due to their design, cycloidal gears are much more resistant to tilting than wave gears. This is particularly beneficial in the case of long lever arms, where high torque stiffness acts on the transmission. High moment stiffness helps minimize elastic deformation and maintain accuracy even under load.

Torsional stiffness

Cycloidal gears are characterized by higher torsional stiffness. They are therefore more resistant to torsion around the longitudinal axis, which results in smaller elastic deformations under the influence of torsional stresses. This has a positive effect on precision. Wave gears also achieve high values, but are designed more for completely backlash-free operation and compact dimensions.

Permissible load

For very heavy loads, cycloidal gears are the best choice. With a rated torque of 28,000 Nm and a maximum dynamic torque of 70,000 Nm, our RV-2800N transmission is the world's largest precision transmission and can effortlessly move entire vehicles. Our rotary tables are also designed with heavy loads in mind: the RS-900A, for example, positions axial loads of up to 9 t with high precision.

Resistance to overload

Both technologies provide significant safety reserves. The emergency stop torque is up to 500% of the rated torque, and in the case of cycloidal gears, optionally up to 800%. This provides high protection against overloads and increases reliability even in difficult conditions.

Installation location and weight

When it comes to installation space and weight, wave gears have the advantage. They are more compact and lighter than cycloidal precision gears, making them particularly suitable for applications where mounting space is limited. This makes them particularly attractive for small axes that require high precision and dynamics despite their compact dimensions.

Direct comparison of properties

Typical applications

Automation Dream Team

Virtually every application, machine or system has major and minor axes. If the larger axes are equipped with cycloidal gears and the smaller ones in the end effector area with wave gears, the highest possible precision can be achieved thanks to the overall coordination of all axes. A true automation dream team.

Selecting the right transmission is crucial for the efficiency and durability of the entire system. If you want to compare cycloidal and wave gears for a specific application, please contact WObit - the official Nabtesco distributor in Poland. Our advisors will help you choose a solution tailored to your technical requirements and working conditions.

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