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Strain Wave Gears
High-Precision zero Backlash Technology

Ring Gear

a cylindrical ring with internal gear teeth


a cylindrical, flexible, thin-walled steel component with external gear teeth

Wave Generator

a plug with an elliptical outer contour on which a radially flexible special ball bearing is mounted

Strain Wave Gears

Strain wave gears comprise only three components: wave generator, flexspline and circular spline. The main character of the gears is the power transmission by means of a flexible element, the flexspline. It is a cylindrical steel component with external gear teeth, which takes on an elliptical form when the wave generator is inserted. In combination with the continuous multiple engagement of the flexible ring and the ring gear, this design achieves absolutely zero backlash, outstanding transmission accuracy and high torsional stiffness.

Strain wave gears are available in two versions: 

  • Hat type gear (HTG)
  • Cup type gear (CTG)

These versions differ only in the design of the flexspline.
The main advantage of the hat type gear is the larger hollow shaft.


The wave generator is generally the drive element of the gearbox. It is inserted into the flexspline so that the gear teeth of the flexible ring and ring gear engage. Either the flexspline or the circular  spline can be used for the gear output. The reduction ratio results from the external gearing of the flexspline having two less teeth than the internal gearing of the ring gear.

How it works

The elliptical wave generator deforms the flexspline by means of the ball bearing. The flexspline in turn engages with the internal gear teeth of the cicular spline in the areas opposite the large elliptical axis. The rotary motion of the wave generator causes displacement of the large elliptical axis and therefore the area where the teeth engage. Since the flexspline has two teeth less than the circular spline, after a half revolution of the wave generator there is a relative motion of one tooth between the flexspline and the circular spline, and a motion of two teeth after one full revolution.

Advantages of Strain Wave Gears:

The design of strain wave gears is simple yet very effective. Due to the numerous advantages of strain wave gears they are used in all areas of drive technology.

Product advantages:

  • Zero backlash throughout the service life
  • Outstanding transmission accuracy and repeatability
  • Small, lightweight design
  • High torque capacity
  • High reduction ratios in one stage
  • High efficiency
  • High torsional stiffness
  • Central hollow shaft is possible
  • Maintenance-free



Whether the requirement is for single components or complete systems:
We also develop and industrialize custom mechatronic drive systems in series applications. 

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