NdFeB Ring Magnets

What Are Neodymium Ring Magnets?

Neodymium ring magnets are ring-shaped NdFeB permanent magnets with a center hole. They are one of the strongest rare earth permanent magnets available today. Due to their unique hollow ring structure, NdFeB ring magnets can provide a stable and uniform magnetic field distribution while direct installation onto shafts, screws, and other mechanical components.This design makes them ideal for rotating assemblies, axial stacked components, and applications that require both precise center positioning and strong magnetic holding force.

Neodymium Ring Magnet Specifications

Ring magnets have stricter requirements for dimensional accuracy. Selecting the appropriate outer diameter (OD), inner diameter (ID), and thickness is essential for ensuring reliable magnetic performance and precise assembly. The following aspects can serve as a reference for your customization choices:

Size Range:

Outer Diameter (OD): Ø1mm – Ø100mm
Inner Diameter (ID): Ø0.5 mm – Ø90 mm
Thickness (Height): 0.5 mm – 40 mm

Note: When customizing ndfeb ring magnets, it is recommended to keep the ID/OD ratio within 0.9. This is particularly important for radially magnetized ring magnets—when the ratio approaches or exceeds 0.7, the risk of cracking during machining and magnetization increases significantly.

Magnet Grades:

To ensure stable magnetic performance across different operating temperature environments, we offer a variety of NdFeB magnet grades:
Standard Grades: N35-N52
High Temperature Grades: 30M-50M, 30H-48H, 30SH-44SH, 30UH-40UH, 30EH-38EH, 30AH

Magnetization Direction：

Depending on different application requirements,neodymium ring magnets typically offer the following magnetization directions:

Axial Magnetization: Magnetic poles are distributed on the top and bottom end faces of the ring magnet. This is the most common magnetization method.

Radial Magnetization: Magnetic poles are distributed on the inner and outer circumferential surfaces of the ring magnet.

Diametrical Magnetization: The magnetization direction is perpendicular to the central axis, with an N pole on one side and an S pole on the other.

Multi-Pole Magnetization: Depending on motor design requirements, multiple pairs of magnetic poles can be magnetized circumferentially on the ring to meet the special application requirements of multi-pole motors, servo systems, and similar applications.

For customers with other special magnetization direction requirements, custom development can also be provided based on specific application scenarios.

Surface Treatment：

Depending on the operating environment, TOPMAG offers a variety of plating options, including nickel-copper-nickel, epoxy resin, zinc, gold, and silver coatings, to meet different requirements such as corrosion resistance, wear resistance, or specific aesthetic needs.

Dimensional Tolerance：

Normally, custom ndfeb ring magnets are manufactured according to the dimensional tolerances specified by the customer. If such specifications are unavailable, our engineering team will evaluate the specific application scenario and recommend appropriate tolerance grades.

The following table provides reference tolerances for different precision grades:

Tolerance Level	Manufacturing Process	OD / ID / Thickness Tolerance	Concentricity Tolerance	Typical Applications
Standard Tolerance	Conventional Machining	±0.05 mm – ±0.10 mm	Approximately ±0.05 mm	General assembly applications
Precision Tolerance	Precision Grinding	±0.01 mm – ±0.03 mm	±0.01 mm – ±0.02 mm	High-precision assemblies requiring excellent dimensional consistency

Applications of Neodymium Ring Magnets

Neodymium ring magnets are widely used in motors, sensors, magnetic couplings, automation equipment, medical devices, and consumer electronics. They provide strong, stable magnetic performance and precise shaft mounting for compact assemblies.

Other Types of Ring Magnets

In addition to NdFeB ring magnets, TOPMAG also supplies ring magnets made from other magnetic materials to meet different performance and cost requirements.

• Ferrite Ring Magnets——Ferrite ring magnets are an economical solution with excellent corrosion resistance, making them suitable for outdoor environments and high-volume applications where ultra-high magnetic strength is not required.

• SmCo Ring Magnets——SmCo ring magnets provide excellent high-temperature resistance and outstanding resistance to demagnetization, making them ideal for demanding high-temperature environments.

• Alnico Ring Magnets——Alnico ring magnets offer excellent temperature stability, although their magnetic strength is relatively lower than NdFeB magnets. They are suitable for applications requiring highly stable magnetic performance over a wide temperature range.

Frequently Asked Questions (FAQ)

Is there any limitation on the inner-to-outer diameter ratio of ndfeb ring magnets?

Yes. The feasible ID/OD ratio depends on the magnet size, material strength, and manufacturing process. Our engineering team can recommend the optimal design based on your application and performance requirements.

How many pole pairs can a multipole ring magnet have?

It depends on the outer diameter. Four to eight pole pairs are common, while higher pole counts require engineering evaluation based on your drawings.

What is the maximum operating temperature of NdFeB ring magnets?

Depending on the NdFeB magnet grade, the maximum operating temperature ranges from 80°C to 220°C.

How are ring magnets mounted on shafts? Is additional fixation required?

Ring magnets are commonly installed using press fitting, adhesive bonding, or mechanical fixtures. The appropriate installation method depends on the operating conditions and application requirements.

What are the lead time and MOQ for custom ndfeb ring magnets?

The MOQ and lead time depend on the product drawings, dimensions, and customization requirements. Contact TOPMAG with your specifications for an accurate technical evaluation and quotation.

Ferrite Magnets