Key Questions to Ask When Ordering Strain Wave Gear

12 May.,2025

 

Product Installation Considerations - Harmonic Drive

Our servo actuator, gearhead, and gearing component products are high performance and are easy to use. Application notes provide an in-depth understanding of key areas.
In addition to the technical data on products found on our product pages we think it is important to communicate the technical information we have produced to help you better understand the strain wave gearing technology, as well as how to size and select the best gear for your application.

ARCSEC DRIVE supply professional and honest service.

Below is some helpful information about our Component Sets and Gear Units.

Component Sets

The following information is directed toward technicians or personnel, who are involved in the assembly or installation of Harmonic Drive® gears.
Refer to recommended housing tolerances and component set drawing for proper installation specifications.

Lubrication

*It is extremely important to closely follow the lubrication requirements provided for your specific model. Most of our manuals can be downloaded here.

Use the recommended lubricants and proper quantity. Replace the lubricant at the recommended service interval.

There are four areas within the gear that require lubrication.

A) Wave Generator Bearing
B) Oldham Coupling (if one is included)
C) Gear Teeth
D) Inner diameter of Flexspline

Proper seals, gaskets, or sealants must be used to contain the small amount of oil that may separate from the grease.
The Component Set has been coated with a rust preventative oil for storage purposes, and must be thoroughly cleaned prior to use.
There are three types of component sets: Cup-Style, Pancake-Style and Silk Hat-Style.

The Cup-Style Gear has a Flexspline that is shaped like a cup.

The Pancake-Style Gear has a Flexspline that is a thin sleeve with gear teeth on the outside diameter. It is basically a cup without the bottom. The Pancake-Style has an additional item called a Dynamic Spline, which appears to be similar to the Circular Spline. The Dynamic Spline has larger chamfers than the Circular Spline. These two items are not interchangeable.

The Silk Hat style features a brim-like mounting surface and large through hole.

Assembly

*It is extremely important to closely follow the assembly instructions provided for your specific model. Most of our manuals can be downloaded here.

The relative perpendicularity and concentricity of the three basic Harmonic Drive® elements have an important influence on accuracy and service life. Misalignments will adversely affect performance and reliability. Compliance with recommended assembly tolerances is essential in order for the advantages of Harmonic Drive® gearing to be fully realized.

Proper lubrication is essential for high performance and reliability. Harmonic Drive® component sets are shipped with a rust- preventative oil. The characteristics of the lubricating grease and oil types approved by Harmonic Drive are not changed by mixing with the preservation oil. It is therefore not necessary to remove the preservation oil completely from the gear components. However, the mating surfaces must be degreased before the assembly.

The Wave Generator must be securely fastened to the input hub to prevent axial movement along the input shaft. The Wave Generator must be assembled concentrically with the Circular Spline to prevent an improper assembly. Refer to the "Dedoidal" section in our full Reducer Catalog.


The surface to which the Circular Spline is clamped, must be clean, flat, and free of debris or burrs. Tighten screws using a torque wrench and use no other locking hardware except the suitable grade LOCTITE sealant or equivalent.

Contact us to discuss your requirements of rv reducer. Our experienced sales team can help you identify the options that best suit your needs.

Model Number

The part numbering method is as follows (space permitting).

SS XX JJJJJJ Q
SS: Size
XX: Ratio
JJJJJJ: Serial Number
Q: Set Number

In order to obtain the published performance specifications, it is essential that the component set remains as a matched set. Note: The three basic components of the gear - the Flexspline, Wave Generator and Circular Spline - are matched and serialized in the factory. Each component within the component set must have the same part number, including the set number. The above number may be required for ordering replacement drives.

Gear Units

The following information is directed toward technicians or personnel, who are involved in the assembly or installation of Harmonic Drive® gears.
Refer to recommended housing tolerances and drawings for proper installation specifications.

  1. Refer to the motor mounting tolerances and gearhead drawing for proper installation specifications.
  2. Wave Generator must be securely fastened to the input hub to prevent axial movement along the input shaft.
  3. Wave Generator must be assembled concentrically with the Circular Spline to prevent an improper assembly. Refer to the "Dedoidal" section in our catalog for more information.
  4. Proper seals, gaskets, or sealants must be used to contain the small amount of oil that may separate from the grease.
  5. Only the specific Wave Generator supplied with each gearhead may be used with that gearhead. These are shipped as a matched set.

For peak performance of the gear, it is essential that the following tolerances be observed when assembly is complete. Pay careful attention to the following points and maintain the recommended assembly tolerances to avoid grease leakage.

  • Warping and deformation on the mounting surface
  • Contamination due to foreign matter
  • Burrs, raised surfaces and location around the tap area of the mounting holes
  • Insufficient chamfering on the mounting pilot joint
  • Insufficient radii on the mounting pilot joint

Modifications

Almost every product from Harmonic Drive is made to order. In fact, more than 70% of our manufactured products are specials.

Some of the most common mechanical modifications are made to the Wave Generator, the Circular Spline or the Flexspline. Our engineering and manufacturing teams also have extensive experience with a variety of materials.

Common performance customizations occur to the accuracy, starting torque and stiffness specifications. Let us know your parameters, and we will work with you to provide the best matched solution.

The Secret of the Strain Wave Gear - New Drive

Clarence Walton Musser was a contemporary man who incorporated both the past and the future into his thinking and inventive ways. His genius and technical understanding resulted in well over 200 patents that were not concentrated or even limited to Musser's special field, mechanical engineering. Whether in the areas of physics, chemistry or biology - the US-American distinguished himself through his wide-ranging interests, with his completely restless mind and analytical abilities.

Equal to Musser's patriotism were ethics and honesty. His intellectual abilities were as legendary as his sense of humour - and so a day with Walt, as friends and acquaintances called him, was always like an adventure. To recognise his genius, it was enough to listen to him. Equally strong in character was his choice of friends. He avoided aloof people and rather had close contact with those he truly liked, regardless of their position in society.

After Musser had devoted himself to aviation in the late s and early s, which resulted in the invention of the ejection seat and the canopy for jet aircraft, among other things, his attention fell on elastic bodies. So he then began his study and research in this field and, in doing so, he sometimes relied on controlled bending and deflection. Later, he applied these to new mechanical designs, structures and concepts - and finally developed the functional principle of the strain wave gear.

Even today, the features of Harmonic Drive® Gears presented above are largely based on the interaction of their simple design, but above all on the unique principle of elastic deformation of gears and the Flexspline respectively. The latter is a high strength, torsionally stiff, yet flexible component that reliably transmits high loads.

The Harmonic Drive® Gear is based on three components. The basis is embodied by the Wave Generator, an elliptical steel disc at the heart of the gear. It has a centric hub and a thin, elliptically deformable special ball bearing. The Wave Generator uses the ball bearing to deform the Flexspline, a deformable cylindrical steel sleeve with teeth arranged radially around the outside. As a rigid and cylindrical outer ring, it is the Circular Spline, which is the third component surrounding both Wave Generator and Flexspline and is equipped with internal teeth.

As the Wave Generator rotates, the large elliptical axis shifts and with it the gear meshing area. The number of teeth themselves is of great importance - the external teeth of the Flexspline have exactly 2 teeth less than the internal teeth of the Circular Spline. Accordingly, during a half rotation of the elliptical Wave Generator, there is a relative movement of one tooth between the Flexspline and the Circular Spline; during a full rotation, there are already two teeth.