FB Series Component-Type Strain Wave Gear

The FB Series takes a fundamentally different approach compared to our enclosed FS and FH units. Instead of providing a pre-sealed gearbox, we supply this series as a four-piece component set consisting of a Wave Generator, a Flexspline, and two Circular Splines.

This format gives equipment designers the freedom to mount the gearing directly inside their own structural housings. Integrating the parts this way strips away unnecessary adapter flanges and extra bearing supports. The immediate result is a remarkably thin axial profile that standard packaged reducers simply cannot match.

Beyond saving space, the FB architecture significantly amplifies torque output. We utilize a dual circular spline configuration that effectively doubles the total area of tooth engagement.

To handle these heavier payloads, we widened the gear teeth on both the flexspline and circular splines to distribute physical stress more evenly. We also equipped the Wave Generator with a reinforced deep groove ball bearing designed specifically to absorb the resulting high radial forces.

Component-Type Architecture

Choosing Between Unit and Component Architectures

While the FS Series arrives as a fully sealed gearbox ready to bolt directly onto an existing robotic arm, the FB Series is built for deep mechanical integration. Instead of adding external bulk, the FB elements embed straight into your custom design.

The circular splines secure into machined pockets within your joint housing. The flexspline fastens to your bespoke output flange. The wave generator presses directly onto the motor shaft.

Option for the FB Series component set over a standard unit type when your engineering priorities include:

Custom Joint Geometry: You are designing a mechanism from the ground up and dictate the exact internal housing dimensions.
Strict Axial Limits: Depth is your primary constraint. Shedding the factory enclosure typically saves 30% to 40% in axial length compared to packaged reducers of equal torque.
Optimized Bearing Layouts: Your larger assembly already features independent bearing supports, rendering any built-in reducer bearings completely redundant.
High-Stiffness Applications: Your positioning tasks demand the specific structural rigidity gains provided by a dual circular spline configuration.

Component-Type Architecture FB Series — Product Overview

FBS‑C‑I Type

Component set (4 parts)
Wider size and ratio range
Withstands extreme pressure
Without grease failure
General integration projects
Custom robot joints
High‑pressure environments

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FBS-U-ⅠType

Component set (4 parts)
Multi‑segment tooth profile
Fatigue pitting area reduced by >30%
Lower friction
Extended service life applications
High‑precision positioning
Continuous‑duty cycles

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Double Circular Spline Design

The defining structural feature of the FB Series is the dual circular spline configuration. A standard cup-type strain wave gear uses one circular spline meshing with the flexspline. The FB adds a second circular spline (S and D) on the opposite side of the flexspline, creating two simultaneous meshing zones.

This doubles the number of teeth in contact at any instant, which:

Increases torsional rigidity without increasing housing diameter
Distributes load across twice the tooth contact area, reducing per-tooth stress
Provides a secondary load path — if one spline experiences momentary overload, the other maintains positional hold
Allows widened tooth profiles on both the Circular Splines and Flexspline, further increasing load capacity

The trade-off is integration complexity: the customer must align two splines during assembly rather than one. Laifual provides alignment fixtures and assembly documentation with every component set.

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Applications

Custom Robot Joints

OEM robot builders integrating strain wave gears into proprietary joint housings. The FB component set eliminates redundant housings and bearings, reducing parts count, assembly labor, and joint mass.

Performance Characteristics

Torsional Rigidity

The dual circular spline configuration provides enhanced torsional stiffness compared with conventional single-spline strain wave gears of the same size. Two meshing zones share torque transmission, improving resistance to torsional deformation and maintaining angular positioning accuracy under fluctuating external loads. This makes the FB Series suitable for precision applications such as metrology rotation stages, antenna positioners, and high-accuracy indexing tables.

Ultra-Flat Profile

By eliminating the factory housing, output bearing, and mounting flange that add depth to a unit-type reducer, the FB component set achieves a profile 30% to 40% thinner than an equivalent-torque FS unit. For robot wrists, gimbal axes, and rotary stages where axial space is measured in single-digit millimeters, this depth reduction is the FB Series’ primary selection criterion.

Integration Flexibility

As a component-type strain wave gear, the FB Series allows integrators to customize housing design, bearing arrangements, sealing solutions, and lubrication systems. This flexibility enables optimized integration for demanding applications, including vacuum equipment, cleanroom systems, and high-temperature environments.

Spec Overview Table

Parameter	FBS‑C‑I Type	FBS‑U‑I Type
Type	Component set (4 parts)	Component set (4 parts)
Circular Splines	Double (S + D)	Double (S + D)
Tooth Profile	Standard multi‑segment	Optimized multi‑segment (fatigue area ‑30%)
Profile	Ultra‑flat	Ultra‑flat
Integration	Customer housing	Customer housing
Application	General automation, custom joints	High‑precision, continuous‑duty

Note: Complete specifications, including size range, reduction ratios, and torque ratings on individual sub-model pages.

Frequently Asked Questions

What is the difference between component type FB and unit type FS strain wave gears?

A unit type FS Series strain wave gear ships as a complete and sealed gearbox equipped with its own housing, output bearing, and mounting flange. It arrives ready to mount immediately. Conversely, a component type FB Series strain wave gear ships as four individual precision parts including the Wave Generator, Flexspline, and two Circular Splines. The customer integrates these components directly into their own housing or mechanism. Select the FB Series when you are building a custom joint from scratch and want to eliminate redundant housings for a thinner and lighter assembly. Opt for the FS Series when you require a gearbox that is fully prepared for instant installation.

What does the double circular spline configuration achieve?

A standard strain wave gear utilizes a single circular spline. The FB Series introduces a second circular spline on the opposite side of the flexspline to completely double the tooth engagement area. This architecture increases torsional rigidity, distributes the mechanical load across significantly more teeth, and provides a secondary load path for enhanced failure redundancy. The only trade off is a more complex assembly process since both splines must be precisely aligned during integration.

When should I choose FBS-U-I over BS-C-I?

Select the FBS-C-I for general integration projects where a wide size and ratio selection matters most. Opt for the FBS-U-I when service life and precision are your absolute top priorities. Its optimized multi segment tooth profile reduces the fatigue pitting area by over thirty percent and lowers sliding friction to significantly extend continuous service intervals.

Do I need special tooling to integrate FB Series components?

Laifual provides alignment fixtures, assembly documentation, and recommended housing tolerance drawings with every FB component set. Standard machine shop capabilities such as CNC milling and cylindrical grinding for bearing seats are entirely sufficient. For first time integrators, the Laifual engineering team offers comprehensive assembly review and on site support for the initial build.

Can the FB Series handle the same torque as the FS Series?

At equivalent size points, the FB Series typically delivers higher torsional rigidity alongside comparable or even higher torque capacity. This is achieved through the double circular spline configuration and widened tooth profiles. However, the ultra flat profile of the FB Series means it is highly optimized for applications where axial depth serves as the primary constraint rather than absolute peak torque. We recommend comparing the published torque ratings on the FBS-C-I and FBS-U-I specification tables directly against your chosen FS reference model.

What is the minimum order quantity for FB Series component sets?

Standard sizes and ratios ship starting from a single unit for prototyping and evaluation purposes. Custom tooth profiles, non standard Circular Spline bore diameters, or modified Wave Generator interfaces are available with minimum order quantities starting at fifty units. Please contact our sales team for a thorough feasibility review and an accurate lead time estimate.