FS Series Cup-Type Strain Wave Gear

The FS Series is a cup-type strain wave gear with external gear teeth on the circumferential wall of the flexspline. It delivers zero backlash, high torque density, and repeatable positioning accuracy across a wide range of precision motion applications.

This cup-type design boasts the maximum torque-to-weight capacity across Laifual's entire strain wave gear range. Standard reduction ratios range from 30:1 to 160: 1, with custom options readily available upon request. All models are lifetime grease-lubricated and sealed at the factory for maintenance-free operation throughout the rated service interval.

For engineering teams working with Harmonic Drive CSF, CSG, or CSD models, the FS Series provides a directly compatible replacement path with equivalent or higher torque ratings at each size point. Laifual has invested 10+ years in strain wave gear R&D, from tooth profile optimization and flexspline fatigue analysis to in-house CNC grinding and Zeiss CMM inspection. Manufacturing is ISO 9001:2015 certified, with CE, RoHS, and REACH compliance across the standard product line.

Multi-Segment Tooth Profile

The FS Series uses a multi-segment continuous arc tooth profile, an upgrade from the conventional double-arc design. Each tooth segment follows a precise curvature that reduces sliding friction at the gear mesh interface, lowering operating temperature and slowing grease degradation.

The five-tooth simultaneous engagement distributes contact stress across a wider area, reducing peak surface pressure.

Measured performance improvements over traditional double-arc profiles:

Load capacity: 15% higher at the same size
Temperature rise: 8 to 10°C lower under continuous load
Fatigue-affected contact area: reduced by >30%
Continuous service life: exceeds 15,000 hours

These gains come from geometry, not exotic materials or coatings. The profile is precision-ground on Laifual’s in-house CNC gear grinding equipment and verified on Zeiss CMM inspection systems.

FSD

FSD Ultra-Flat Sizes 14-32
Same torque class,
FSD runs 8-10°C cooler at rated load
6-axis robot arms, SCARA, general automation

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FSN Lightweight

Sizes 5–40
50% weight reduction vs FSG;
No direct Harmonic Drive equivalent
End effectors, desktop robots
UAV gimbals, exoskeletons

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FSG

FSG High‑Torque (Sizes 14–50)
FSG delivers up to 30% higher torque at same frame size
Heavy‑duty joints
General automation
Press tending
Palletizing

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FSS

FSS Standard (Sizes3–40)
FSS extends down to size3 for micro‑robotics applications
Collaborative robots
Medical devices
Optics

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Precision Motion Control

Flexspline Deformation Control

The cup-type flexspline deforms elliptically under the wave generator, creating two opposing zones of full tooth engagement per revolution. The deformation curve is tuned to keep the engagement angle stable across the rated torque range, reducing the stress amplitude that drives fatigue crack initiation.

This control also limits torsional windup, so the output maintains angular accuracy as load fluctuates. Backlash remains at or below 20 arc seconds throughout rated life.

Ratio Selection and Stiffness

By adjusting the wave generator profile and tooth count difference, reduction ratios from 30:1 to 160:1 are available. Higher ratios increase output torque capacity proportionally while maintaining the same housing diameter.

Torsional stiffness scales with size and ratio. For example, FSD-25 at 50:1 achieves K1=2.0×10⁴ N·m/rad; at 100:1 it reaches 2.7×10⁴ N·m/rad. Full stiffness data per size and ratio is available in the technical specifications on each sub-model page.

Service Life and Reliability

Rated for 9,000 to 15,000 hours of continuous operation depending on model and load conditions. This rating assumes rated torque at 2,000 rpm input, with lifetime grease lubrication. No re-greasing or maintenance is required during the rated service interval.

Accelerated life testing at 1.5× rated torque confirms that the multi-segment tooth profile extends fatigue life beyond the rated 15,000 hours. Contact Laifual engineering for test reports specific to your load profile.

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Applications

Industrial Robots

Six-axis robots, SCARA robots, and palletizing systems. Zero-backlash eliminates positioning drift at reversal points, critical for welding, assembly, and pick-and-place.

Spec Overview Table

Parameter	FSD Ultra‑Flat	FSG High‑Torque	FSN Lightweight	FSS Standard
Benchmark Model	CSD	CSG	—	CSF
Size Range	14 to 32	14 to 50	5 to 40	3 to 40
Reduction Ratio	50:1 to 100:1	50:1 to 160:1	50:1 to 160:1	30:1 to 160:1
Rated Torque @2000rpm	3.7 to 96 Nm	7 to 529 Nm	0.4 to 294 Nm	0.06 to 294 Nm
Back Gap	≤20 arc sec	≤20 arc sec	≤60 to ≤20	≤60 to ≤20
Weight	0.37 to 2.4 kg	0.51 to 7 kg	0.025 to 4.6 kg	0.025 to 4.6 kg
Design Life	9,000~10,000h	10,000~15,000h	10,000~15,000h	10,000~15,000h

Note: The data in the table are representative values within the size range. For complete specifications, please refer to the respective sub-model pages.

Frequently Asked Questions

How do FS Series models compare to Harmonic Drive CSF, CSG, and CSD?

FSS Standard corresponds to CSD, offering balanced torque and precision for general robotics. FSG corresponds to CSG with 30% higher torque capacity. FSD Ultra-Flat corresponds to CSF, providing a thinner cross-section for space-constrained designs. FSN Lightweight offers weight reduction of up to 50% compared to standard models, designed for collaborative robots and end effectors. Mounting dimensions are designed for drop-in compatibility; contact our engineering team with your current model number for a detailed interchange check.

What is the lead time for FS Series orders?

Standard models (sizes 14 to 32, ratios 50:1 to 100:1) ship within 2 to 4 weeks from order confirmation. Custom ratios, non-standard mounting flanges, or large quantities (500+ units) require 6 to 8 weeks. Rush orders can be accommodated at shorter lead times depending on production capacity. Contact sales for current availability.

What differentiates the multi-segment tooth profile from standard double-arc designs?

The multi-segment continuous arc profile uses five teeth in simultaneous engagement instead of two to three in conventional double-arc designs. This distributes contact stress over a larger surface area, reducing peak pressure by more than 30%. The result is lower operating temperature, slower grease degradation, and 15,000+ hour continuous service life without re-lubrication.

Can Laifual customize the FS Series for my application?

Yes. Common customizations include non-standard reduction ratios, modified output flange patterns, special output shaft configurations, alternative bearing arrangements for high radial loads, and custom housing materials for vacuum or cleanroom environments. Minimum order quantities for custom variants start at 50 units. Engineering review takes 3 to 5 working days after receiving your specification.

What is the maximum input speed for FS Series reducers?

Permissible maximum input speed is model and size dependent: 10,000 rpm for sizes 5 to 20, 8,500 rpm for size 14, 7,300 rpm for size 17, 6,500 rpm for size 20, 5,600 rpm for size 25, 4,800 rpm for size 32, and 4,000 rpm for size 40. For continuous operation, we recommend operating at or below the rated average input speed (3,500 rpm for most models).

Do FS Series reducers require maintenance or re-greasing?

No. FS Series units are lifetime lubricated at the factory with a specially formulated strain wave gear grease and sealed for the rated service life. Under normal operating conditions (rated torque, rated speed, ambient temperature below 40°C), no re-greasing or maintenance is required.

What certifications does Laifual hold for the FS Series?

Laifual is ISO 9001:2015 certified. RoHS and REACH compliance are standard across the product line. dditional regional certifications are available on request. Full certification documentation is provided with each order shipment. Also, we provide test reports to help customers evaluate and verify product performance.

How do I request samples or arrange a trial order?

Trial orders of 1 to 5 units are available for evaluation. Standard models ship from stock within 2 weeks. For custom configurations, an NRE (non-recurring engineering) fee may apply depending on the scope of modification. Payment terms: 50% deposit with order, 50% before shipment. Contact sales@laifualdrive.com or WhatsApp +86 13632529084 to initiate a sample request.