STEPPERONLINE currently offers 44 models of harmonic gearboxes, divided into five series: HSS-I, HHT-I, HHT-III, HHT-IV, and HHD-I.
A harmonic gearbox consists of three primary components: the wave generator, the flexspline, and the circular spline.
Wave generator: Composed of a flexible bearing and an elliptical cam, it is typically mounted at the input end of the gearbox. The inner ring of the flexible bearing is fixed to the cam, while the outer ring is elastically deformed into an elliptical shape by the ball bearings.
Flexspline: A flexible, thin-walled elastomeric component with an external gear ring, typically mounted at the output end of the gearbox.
Circular spline: A rigid annular component with an internal gear ring, generally featuring two more teeth than the flexspline. It is usually fixed to the gearbox housing.
Features of harmonic gearboxes:
- High precision: The precision of a harmonic gearbox is measured in arcseconds (arcsec), whereas the precision of a planetary gearbox is measured in arcminutes (arcmin). The maximum backlash of our conventional EG series planetary gearbox is 20 arcmin (1,200 arcsec), while the maximum backlash of a harmonic gearbox is only 20 arcsec.
- Large transmission ratio: The transmission ratio of a single-stage harmonic gear ranges from 30 to 500, and the structure is simple. Three basic components on the same axis can achieve a high reduction ratio.
- High load-bearing capacity: In harmonic transmission, tooth meshing involves surface contact, and a relatively large number of teeth are engaged simultaneously. This results in a low load per unit area, giving harmonic gearboxes a higher load-bearing capacity than other transmission types such as planetary gearboxes.
- Compact size and light weight: Compared with conventional gear devices, harmonic gearboxes are significantly smaller and lighter, enabling miniaturization and weight reduction.
- Smooth transmission with no impact and low noise.
The following sections describe the features of each harmonic gearbox series.
HSS-I Series
Product features:
- The flexspline features a cup-shaped standard cylindrical structure with a high-rigidity full-roller crossed bearing.
- LS tooth profile design, proprietary CMP heat treatment process, and 1 µm track fine grinding deliver higher rigidity, higher precision, and higher torque capacity.
- Compact and simple structural design with zero backlash, direct motor connection, and easy installation.
- Coaxial input and output.
- Excellent positioning accuracy and rotational accuracy.
HHT-I Series
Product features:
- The wave generator adopts an integrated structure, resulting in a compact overall design.
- Supports two mounting configurations: fixing the circular spline and outputting from the flexspline, or fixing the flexspline and outputting from the circular spline.
- Direct motor connection for easy installation.
HHT-III Series
Product features:
- Features a large-diameter hollow shaft through the center of the wave generator cam.
- The gearbox incorporates an internal support bearing and a fully sealed structure for easy installation.
HHT-IV Series
Product features:
- The wave generator cam includes a dedicated input shaft, compatible with various input configurations.
- The gearbox incorporates internal support bearings and a fully sealed structure for easy installation.
HHD-I Series
The HHD series flexspline features an ultra-thin hollow flange structure. Without compromising product performance, the axial length of the HHD-I is reduced by approximately 50%. The overall design achieves an ultra-flat profile, making it compact and lightweight. It is ideally suited for applications with strict constraints on gearbox thickness. Installation note: Supports two mounting configurations — fixing the circular spline and outputting from the flexspline, or fixing the flexspline and outputting from the circular spline.
Product features:
- Ultra-thin profile
- Compact and simple design
- High torque capacity
- High rigidity
- Excellent positioning accuracy and rotational accuracy