Harmonic Drive

The strain wave gear: heart of a precision joint

Harmonic Drive has been tied to the history of the strain wave gear from the start: the company's website links the technology to the invention of C. Walton Musser. The German company Harmonic Drive SE is based in Limburg an der Lahn, and the group also operates in Japan and the USA. Its range is split into three lines: Harmonic Drive gears, mechatronics (integrated motor–gearbox units) and planetary gears. The company lists these industries: robotics and automation, medical technology, aerospace and defense, and general machinery.

How it works and what the catalog shows

A flexible, thin-walled cup-shaped toothed sleeve (the flexspline) has a slightly smaller pitch diameter than the rigid circular spline and is deformed by a wave generator. The mechanism is described in “Actuators in Humanoid Robots”. The CSG/CSF catalog shows that the CSF series is the standard version and the CSG is a higher-torque version: the manufacturer cites a 30 percent increase in torque capacity and L10 life extended from 7,000 to 10,000 hours. A 30:1 ratio was added to the CSF line. Rated torque is defined in the catalog as the permissible continuous load at 2000 rpm input speed, with separate limits given for repeated peak, average and momentary peak torque — exactly the entries to look for when you check “How to Read a Robot Datasheet” before buying.

The materials cover dozens of documents: the CSF and CSG series and their mini and supermini versions, SHF/SHG with a hollow shaft, differential gears, rack-and-pinion units, FHA, RSF, PMA, SHA and LA actuators, HPN planetary gears and motors. The catalogs also show actuators with integrated gearing, motor and encoder, which the manufacturer offers as ready-made joint modules. In 2024–2025 the company announced, among other things, gearboxes with an integrated torque sensor.

In which robots

Strain wave gears are a classic choice in industrial arms and cobots, where zero backlash and torsional stiffness matter; see also “What Is a Cobot and How Does It Differ from an Industrial Robot”. In humanoids they work in joints that need precision at moderate load and where weight matters, for example the shoulder and wrist of humanoid robots. We do not assign specific robot models to specific gearboxes, because manufacturers rarely disclose parts lists. The main competitor in this class is Nabtesco, and related motion components are offered by, among others, Spinea and IKO. A somewhat different path — quasi-direct drive without such a gearbox — is represented by CubeMars.

Cost and Poland

A strain wave gear is usually an expensive part of a joint: precision machining of the thin sleeve drives up the price, as discussed in “How Much Does a Humanoid Robot Cost in 2026”. We give no prices because we have no price list. According to the distributor's own information, the Warsaw company Ultra Robotics, active since 2007, is an official distributor of Harmonic Drive and of Elmo Motion Control drives; it is worth verifying at the source. For domestic integrators and machine builders, from factories to laboratories, that is a natural entry point.