Strain-wave (harmonic) gear
Laifual Drive FSD (FS ultra-thin) strain-wave (harmonic) gear
Flat, short-length cup-type strain-wave gear in sizes 14 to 32 with ratios 50–100, rated 3.7–96 Nm and up to 420 Nm momentary, backlash 20 arcsec or less; listed as the CSD-equivalent type.
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Key specifications
| Rated torque | 3.7–96 Nm |
|---|---|
| Ratio | 50–100:1 |
| Backlash (max) | 0.33 arcmin |
| Sizes | 14, 17, 20, 25, 32 |
| Rated life | 10,000 h |
| Momentary torque max | 420 |
| Max input | 8,500 |
| Backlash | ≤20 arcsec |
Summarised in our own words from Zhejiang Laifual Harmonic Drive Co., Ltd. (HKEX: 03952)'s published data; series maxima, individual models vary. Last checked 2026-10-30. Source 1
Notes on this data
Start/stop peak torque column could not be read reliably, so omitted. Life 9,000 h at ratio 50.
Specify Motion is not affiliated with Zhejiang Laifual Harmonic Drive Co., Ltd. (HKEX: 03952). Laifual Drive and FSD (FS ultra-thin) are used only to identify the product. Comparisons use published figures; always confirm against the current datasheet.
Laifual Drive FSD (FS ultra-thin) replacement and alternative options
Use these supply-network options as a starting point for an engineering check. We can also help source the original Laifual Drive part. Published series figures do not establish an exact-model or drop-in replacement: confirm ratings, fit, interfaces and approvals for your application.
Ultra-flat cup-type strain-wave gear with a very short axial length, light weight and high stiffness for its size.
| Published maximum | FSD (FS ultra-thin) | LCD |
|---|---|---|
| Rated torque | 96 Nm | — |
| Ratio (max) | 100:1 | 500:1 meets or exceeds |
| Backlash (lower is better) | 0.33 arcmin | — |
Cup-type strain-wave gear component sets for building your own joint; the LCSG high-torque version lifts capacity by around 30% over the standard LCS.
| Published maximum | FSD (FS ultra-thin) | LCS / LCSG |
|---|---|---|
| Rated torque | 96 Nm | — |
| Ratio (max) | 100:1 | 500:1 meets or exceeds |
| Backlash (lower is better) | 0.33 arcmin | — |
Ultra-flat hollow-shaft strain-wave gear, combining a very low axial height with a through-bore for wiring.
| Published maximum | FSD (FS ultra-thin) | LHD |
|---|---|---|
| Rated torque | 96 Nm | — |
| Ratio (max) | 100:1 | 500:1 meets or exceeds |
| Backlash (lower is better) | 0.33 arcmin | — |
Figures are the highest published for each series and are not always measured the same way. A higher figure is not automatically a better choice: mounting, duty cycle, feedback, connectors and approvals matter too. An engineer will check the fit against your application before recommending anything.
Typical applications
What a strain-wave (harmonic) gear is
A strain-wave gear, often called a harmonic gear, reduces speed using three parts: an elliptical wave generator, a thin flexible toothed cup or hat called the flexspline, and a rigid circular spline with internal teeth. The wave generator deforms the flexspline so its teeth engage the circular spline at two points. Because the flexspline has typically two fewer teeth, each input turn advances it slightly, giving ratios of about 30:1 to 160:1 in one stage, with near-zero backlash.
When engineers choose a strain-wave (harmonic) gear
Choose a strain-wave gear for compact, lightweight, high-ratio reduction with near-zero backlash, such as robot joints, cobots, medical robots, aerospace and optics. Hollow versions allow cables through the centre. The trade-offs are torsional stiffness at low load, which is lower than some alternatives, limited input speed and the risk of tooth ratcheting under overload. For shock loads and heavy base joints, cycloidal reducers are often preferred.
How to specify the Laifual Drive FSD (FS ultra-thin)
Send these with your enquiry and an engineer can confirm the right FSD (FS ultra-thin) variant or an equivalent:
- Ratio (:1)
- Rated, peak and momentary torque (Nm)
- Input speed limits (rpm)
- Torsional stiffness (Nm/arcmin)
- Hysteresis and accuracy (arcmin)
- Component set or housed unit
- Hollow shaft diameter and output bearing loads
Common mistakes to avoid
- Exceeding momentary torque and ratcheting the teeth
- Ignoring low-load stiffness in precision control
- Poor housing tolerances for component sets
- Using the wrong lubricant or quantity
Laifual Drive FSD (FS ultra-thin): frequently asked questions
Can you help replace Laifual Drive FSD (FS ultra-thin) or source the original?
Send the full model code, quantity and required date. Our engineers can check original-part availability and assess suitable alternatives, including Motion Control Products options where appropriate. We confirm compatibility and any changes needed before recommending a replacement.
What is the Laifual Drive FSD (FS ultra-thin)?
Flat, short-length cup-type strain-wave gear in sizes 14 to 32 with ratios 50–100, rated 3.7–96 Nm and up to 420 Nm momentary, backlash 20 arcsec or less; listed as the CSD-equivalent type. Published series figures include rated torque 3.7 Nm, rated torque 96 Nm, ratio 50:1, ratio 100:1. It is made by Zhejiang Laifual Harmonic Drive Co., Ltd. (HKEX: 03952); Specify Motion can help source it or propose an equivalent.
Who makes the Laifual Drive FSD (FS ultra-thin)?
The Laifual Drive FSD (FS ultra-thin) is made by Laifual Drive (Zhejiang Laifual Harmonic Drive Co., Ltd. (HKEX: 03952)) and is listed here for engineers comparing options. Specify Motion is not affiliated with Zhejiang Laifual Harmonic Drive Co., Ltd. (HKEX: 03952); brand names are used only to identify the product.
What is the rated torque of the Laifual Drive FSD (FS ultra-thin)?
The published series minimum rated torque is 3.7 Nm. Individual models and sizes in the FSD (FS ultra-thin) range vary, so check the exact variant against your duty cycle, mounting and environment, or ask our engineers to confirm the right size for you.
Is there an alternative to the Laifual Drive FSD (FS ultra-thin)?
We can assess suitable replacement options. On published figures, LeaderDrive LCD and LeaderDrive LCS / LCSG are options to assess from our supply network. An engineer confirms the fit against your application before recommending anything.
Why do strain-wave gears have near-zero backlash?
The flexspline teeth are preloaded into the circular spline teeth by the elliptical wave generator, and many teeth engage at once. There is no clearance between teeth at the engagement zones, so backlash is close to zero. Lost motion comes mainly from elastic deflection.
What is the difference between a strain-wave component set and a housed unit?
A component set is the wave generator, flexspline and circular spline, which the machine builder mounts in its own housing with bearings. A housed unit adds a housing, output bearing and seals. Component sets save weight and space; housed units are easier to integrate.
Further reading: Harmonic vs planetary vs cycloidal · How to select a gearbox · Gearboxes and harmonic drives
Other strain-wave (harmonic) gear series
Engineer support
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