Harmonic Drive® Strain Wave Gear

Whether enclosed in a housing, employed as an actuator with motor and encoder, or as components in customer-specified configurations with specific materials or design elements, the flexibility of strain wave gears makes them suitable for a wide range of applications. However, there is one aspect, in particular, that has remained constant for decades, and this is the principle by which the Harmonic Drive® strain wave gear functions.

The Harmonic Drive® strain wave gear is made up of three basic components. These are first of all the so-called wave generator, an elliptical steel disc that forms the heart of the gear unit, which has a centric hub and a special thin, elliptically deformable ball bearing. The wave generator is also connected to the motor shaft. Secondly, the wave generator consists of the flexspline – a deformable, cylindrical steel bushing with teeth arranged around its outer circumference – and the circular spline. The latter surrounds both the wave generator and the flexspline as a rigid, cylindrical outer ring, with teeth along its inner circumference. What is significant is the number of teeth – the outer toothing of the flexspline has fewer teeth than the inner toothing of the circular spline. The difference in number is frequently two.

The central features and advantages of the strain wave gear compared to other, more conventional types of gear unit, are primarily due to the combination of its simple construction and the unique principle of elastic deformation found in steel gear wheels. Harmonic Drive® gears display absolute play-free performance throughout their service life and maintain a high level of torsional rigidity over the whole torque range. With smaller dimensions and a lower weight compared with conventional gear types, they are suitable for use in lighter and more compact applications and systems. Owing to their high reduction ratios and the fact that they consist of three basic components and have a coaxial orientation, strain wave gears can be easily integrated into existing applications.

Outstanding features

Zero backlash

Harmonic Drive® Gears boast no increase in backlash throughout their lifetime.

Excellent positioning accuracy and repeatability

Harmonic Drive® Gears come with excellent positioning accuracy of less than one minute of arc and a repeatability of a few arc seconds.

Small size and light weight

Harmonic Drive® Gears are much more compact and lighter than conventional gears.

Central hollow shaft

Harmonic Drive® Gears offer the possibility of a central hollow shaft. Cables, supply lines, laser beams, etc., can be easily passed through the hollow shaft.

High rations in one stage

With only three components, ratios from 30:1 to 320:1 can be achieved in one stage.

High reliability and long life

Harmonic Drive® strain wave gears reach far higher mean time between failures (MTBF) values than other gear types.

Strain Wave Gear explained

Whether on the seabed, in production halls or in the vastness of the universe: Harmonic Drive® gearboxes and actuators withstand the most diverse environmental conditions - including yours. The basis of their success is special properties which are combined by our Strain Wave Gear Principle and thus formed into an efficient unit.

Find out more about the Strain Wave Gear Principle in the video.


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