Alternatives to Harmonic Drive gears and actuators

In short:Strain-wave gear component sets, hollow-shaft gear units and harmonic servo actuators from other makers can replace many Harmonic Drive parts, provided the size, mounting interface, torque ratings, stiffness and life are checked against your duty cycle rather than the part number alone.

What Harmonic Drive makes

Harmonic Drive is the name most engineers use for strain-wave gearing, and the brand is closely associated with the technology. The group is led from Japan by Harmonic Drive Systems Inc., with Harmonic Drive SE in Limburg, Germany serving Europe and Harmonic Drive LLC in Beverly, Massachusetts serving North America. Harmonic Drive and Harmonic Planetary are registered trademarks of their owner; “strain-wave gear” is the generic term.

The range covers cup-type component sets (CSF, CSG and the flat CSD), silk-hat sets with a large hollow centre (SHF, SHG), housed gear units with integrated output bearings (CPU, SHD), Harmonic Planetary servo gearheads (HPG, HPN), and hollow-shaft servo actuators such as FHA-C, SHA-SG, SHA-CG and RSF. These parts are found in robot joints, semiconductor handling, machine tool indexers, aerospace mechanisms and medical devices.

Why engineers look for a Harmonic Drive alternative

Most enquiries are not about performance. The common reasons are:

• Lead time. A production build cannot wait on one size of one gear set.
• Second source. Many OEMs need two approved suppliers for any part that can stop a line.
• Budget. Cost-down programmes look again at every high-value component in a joint.
• Form factor. A design may need a flatter gear, a larger bore for cabling, or an actuator with the servo drive built in.
• Interface. A move to EtherCAT or a different encoder protocol can be easier with a different actuator than with a new drive.

Harmonic Drive equivalents: what to check

A strain-wave gear is only equivalent if it fits the joint and survives the duty cycle. Check these in order:

1. Construction. Cup, silk-hat or pancake; component set or unit with its own output bearing.
2. Size and ratio. Same nominal size and ratio is the starting point, not the end of the check.
3. Mounting interface. Circular spline and flexspline pilots, bolt circles, axial length, and the wave generator bore, keyway and hub style.
4. Torque ratings. Rated torque, repeated peak (acceleration) torque, momentary peak (emergency stop) torque and ratcheting torque, each against your load profile.
5. Speed. Maximum and average input speed, which drive heat and lubricant life.
6. Stiffness and accuracy. Torsional stiffness across the low, middle and high torque regions, hysteresis loss, lost motion and transmission error.
7. Output bearing. For units, moment load capacity and tilting stiffness.
8. Lubrication and life. Grease type, orientation limits, operating temperature and the rated life basis the maker uses.

For actuators, add hollow-bore diameter, motor voltage, encoder type and resolution, brake, drive compatibility and IP rating.

Strain-wave and harmonic alternatives in our supply network

For component sets, the LeaderDrive range covers the same constructions. The LCS / LCSG cup-type sets are for building your own joint, with LCSG the high-torque version; LHS / LHSG hollow-shaft units suit designs that route cables through the gear; and the ultra-flat LCD and LHD series answer the same need as short-length cup and hollow designs. All four list ratios from 30:1 to 500:1 across the range.

For complete joints, the MAH hollow-shaft harmonic actuator combines strain-wave gearing, motor, encoder and brake in six frame sizes from 48 VDC to 220 VAC. The MAT large-bore actuator increases the through-hole to 45 mm. Where the drive should sit in the joint, the MGM actuator has an integrated EtherCAT servo drive with STO, and the compact MGU robot-joint actuator adds dual 20-bit encoders and an optional torque sensor.

If the application is a servo gearhead rather than a joint, a precision planetary such as the Apex Dynamics AD / ADR (published accuracy below 1 arcmin) or the Wanshsin WSH may be the better fit. Our guides on harmonic vs planetary vs cycloidal gearing, how to select a harmonic actuator and frameless motor sizing for robot joints cover the selection in more depth.

How the comparison below works

The table under this text compares every Harmonic Drive series we hold data for with the closest product from our supply network, using published figures only. “Equivalent” means a product that meets the stated specification for your application, confirmed by one of our engineers; it does not mean the two parts are identical. Specify Motion is not affiliated with, authorised by or endorsed by Harmonic Drive, and no manufacturer logos are used. Product names appear only to identify the parts being compared.

If you send the part number and duty cycle, we will tell you plainly whether a like-for-like alternative exists or whether the original is the right part to keep.