Circular Spline: Positional Accuracy ≤30 arc-sec

Component Specifications

Definition

The Circular Spline is a thin-walled, flexible cylindrical gear component in Harmonic Drive gear systems that engages with the Wave Generator and Flexspline to create controlled elastic deformation, enabling high reduction ratios (typically 50:1 to 320:1) with zero-backlash, high torque capacity, and exceptional positional accuracy through harmonic motion principles.

Working Principle

The Circular Spline remains stationary as the fixed outer gear. The Wave Generator (elliptical cam) deforms the Flexspline, causing its teeth to engage progressively with the Circular Spline's internal teeth. This creates a relative rotational motion between components through elastic deformation rather than conventional sliding contact, resulting in smooth, precise motion transmission with minimal wear.

Materials

High-strength alloy steel (SCM415, SCM420, SNCM220) with carburizing or nitriding surface hardening (HRC 58-62), stainless steel (SUS304, SUS630) for corrosion resistance, or special alloys for extreme environments. Surface finish: Ra 0.8μm or better.

Technical Parameters

Parameter	Typical range	Notes & selection driver
Module	0.2-2.0
Backlash	≤1 arc-min (often zero)
Lubrication	Grease (Molykote, Kluber) or oil bath
Reduction Ratio	50:1 to 320:1
Positional Accuracy	≤30 arc-sec
Torsional Stiffness	5-50 Nm/arc-min
Operating Temperature	-40°C to +120°C

Ranges are indicative industry figures for RFQ preparation, not a supplier commitment. Confirm every value and standard with the legal manufacturer before ordering.

Standards

ISO 1328-1, DIN 3960, JIS B 1702, AGMA 2000

Parent Products

This component is used in the following industrial products

Harmonic Drive Gears

High-precision gear reduction system using elastic deformation for motion transmission

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Engineering Analysis

Risks & Mitigation

Fatigue failure from cyclic stress concentration
Tooth wear from improper alignment
Corrosion in harsh environments
Thermal expansion mismatch
Lubrication degradation

FMEA Triads

Trigger: Excessive cyclic loading beyond fatigue limits
Failure: Crack initiation and propagation in tooth root
Mitigation: Implement load monitoring, use S-N curve based design, apply shot peening to compressive stress layer

Trigger: Misalignment during assembly
Failure: Uneven tooth contact leading to premature wear
Mitigation: Use precision alignment fixtures, laser alignment verification, thermal compensation design

Trigger: Inadequate lubrication or contamination
Failure: Increased friction, overheating, and surface degradation
Mitigation: Sealed housing design, scheduled lubrication maintenance, particle filtration systems

Industrial Ecosystem

Compatible With

Typical Suppliers & Equivalents

Compliance & Inspection

Tolerance

Tooth profile tolerance: IT4-IT5, Concentricity: ≤0.01mm, Surface roughness: Ra ≤0.8μm

Test Method

Coordinate measuring machine (CMM) verification, backlash measurement with torque application, fatigue testing per ISO 6336, thermal cycling validation

Procurement Evaluation Criteria

A practical evidence checklist for RFQ preparation and supplier evaluation.

Technical documentation

Request current drawings, revision history, and a signed specification sheet.

Manufacturing capability

Verify equipment lists, process limits, capacity, and representative production evidence.

Inspection readiness

Confirm test methods, calibrated equipment, sampling plans, and traceable reports.

Supplier transparency

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Manufacturers of Circular Spline

Manufacturer profiles associated with Circular Spline.

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Frequently Asked Questions

What is the main advantage of Circular Spline in Harmonic Drives?

It enables zero-backlash operation through elastic deformation rather than sliding contact, providing exceptional positional accuracy and repeatability unmatched by conventional gears.

How does tooth engagement differ from traditional gears?

Approximately 30% of teeth engage simultaneously (vs 1-2 in spur gears), distributing load evenly across multiple teeth for higher torque capacity and smoother operation.

What maintenance is required for Circular Splines?

Minimal maintenance: periodic lubrication every 5,000-10,000 hours with specified grease, contamination protection, and avoidance of shock loads exceeding rated capacity.

Data Basis

Editorial classification, named public sources where available, and source-reviewed manufacturer records. See the editorial policy.

Preliminary Technical Classification

This page supports structured research, RFQ preparation, and supplier evaluation. It does not replace buyer-led supplier qualification, standards review, or technical approval.

Circular Spline