Ring Gear (Internal Gear): Module Range 1-10 mm

Component Specifications

Definition

The ring gear, also known as an internal gear, is a stationary or rotating annular gear with teeth cut on its inner circumference. In planetary gear reducers, it serves as the outer gear that meshes with multiple planet gears orbiting around a central sun gear. This configuration provides high torque density, compact design, and multiple gear reduction ratios within a single stage. The ring gear's internal teeth engage with the planet gears' external teeth to transfer rotational motion and torque while maintaining precise alignment and load distribution across the gear system.

Working Principle

The ring gear operates on the principle of epicyclic gearing, where it either remains stationary (in fixed carrier designs) or rotates (in rotating carrier designs) while engaging with planet gears. As the sun gear drives the planet gears, they rotate and orbit within the ring gear's internal teeth, creating torque multiplication and speed reduction. The gear ratio depends on the number of teeth on the ring gear relative to the sun gear, following the formula: Reduction Ratio = (Ring Gear Teeth / Sun Gear Teeth) + 1.

Materials

Typically manufactured from case-hardened alloy steels (e.g., AISI 8620, 20MnCr5) or through-hardened steels (e.g., AISI 4140, 4340) with surface hardness of 58-62 HRC. High-precision applications may use carburized or nitrided steels. Alternative materials include ductile iron for cost-sensitive applications or specialized alloys for corrosive environments.

Technical Parameters

Parameter	Typical range	Notes & selection driver
Backlash	0.05-0.20 mm (adjustable based on application)
Module Range	1-10 mm
Tooth Profile	Involute (standard), cycloidal (special)
Accuracy Grade	ISO 1328 Class 5-8, AGMA Q10-Q13
Heat Treatment	Case hardening, induction hardening, or through hardening
Pressure Angle	20° (standard), 14.5° or 25° (special)
Surface Finish	Ra 0.8-3.2 μm

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, DIN 3960, AGMA 2000, JIS B 1702

Parent Products

This component is used in the following industrial products

Planetary Gear Reducer

A compact, high-torque gear reduction mechanism that transmits and reduces rotational speed within a slewing unit.

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Engineering Analysis

Risks & Mitigation

Tooth fatigue failure
Pitting and spalling
Misalignment wear
Inadequate lubrication
Thermal expansion issues
Backlash increase over time

FMEA Triads

Trigger: Insufficient lubrication or contaminated lubricant
Failure: Accelerated tooth wear, scoring, and premature failure
Mitigation: Implement scheduled lubrication maintenance, use filtration systems, monitor oil quality regularly

Trigger: Misalignment during assembly or operation
Failure: Uneven load distribution, localized tooth wear, reduced efficiency
Mitigation: Precision alignment during installation, use of alignment tools, regular inspection of mounting surfaces

Trigger: Excessive torque or shock loads
Failure: Tooth bending fatigue, cracking, or complete tooth breakage
Mitigation: Proper torque calculation during design, installation of overload protection devices, regular load monitoring

Industrial Ecosystem

Compatible With

Typical Suppliers & Equivalents

Compliance & Inspection

Tolerance

Tooth profile tolerance: ±0.01-0.03 mm, Runout tolerance: 0.02-0.05 mm, Tooth spacing error: ≤0.015 mm

Test Method

Coordinate measuring machine (CMM) inspection, gear rolling test, hardness testing (Rockwell C), surface roughness measurement, ultrasonic testing for internal defects

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 Ring Gear (Internal Gear)

Manufacturer profiles associated with Ring Gear (Internal Gear).

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Compiled and source-reviewed by the CNFX editorial team. Each manufacturer above links to the page on that company's own website where the product is listed, with the date we checked it. How we source and review

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Frequently Asked Questions

What is the difference between a ring gear and an internal gear?

In planetary gear systems, 'ring gear' and 'internal gear' are often used interchangeably, but technically, the ring gear refers specifically to the internal gear component within planetary arrangements, while internal gear can describe any gear with teeth on the inner circumference in various applications.

How do you calculate the reduction ratio with a ring gear?

The reduction ratio in a planetary gear system with a fixed ring gear is calculated as: (Number of ring gear teeth / Number of sun gear teeth) + 1. For example, with 100 ring gear teeth and 20 sun gear teeth: (100/20) + 1 = 6:1 reduction ratio.

What maintenance does a ring gear require?

Regular inspection for tooth wear, pitting, or scoring; proper lubrication with EP gear oils; monitoring of backlash and alignment; and periodic cleaning to remove contaminants. Replacement is typically required when tooth wear exceeds 10% of tooth thickness or when surface damage affects meshing performance.

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.

Ring Gear (Internal Gear)