Material System
Magnet Geometry
Ring
Ring magnets are specified by outside diameter, bore diameter and axial height. A ring describes the geometry; axial, diametrical, radial and multipole describe magnetic requirements. The selected grade, orientation and tooling determine which pattern is feasible.
One geometry, four magnetic decisions
A ring is specified by three dimensions — outside diameter, bore diameter and height — and then by how it is magnetized, which is a separate decision with its own drawing consequences. The three dimensions describe the geometry. Axial, diametric, radial and multipole describe what the part has to do. A ring drawing that carries the dimensions and not the magnetic direction is half a specification, because the magnetizing fixture is built from the second half.
The radial wall is where the flux crosses
The wall is the material between the outside diameter and the bore, and on a radially magnetized ring it is the dimension the flux crosses. State it directly, or let it be read as OD minus ID over two — but state it, because a thin wall on a large diameter and a thick wall on a small one are not the same proposition for the same outside diameter. The wall is also what has to survive pressing, so it is read before the route is chosen rather than after.
One piece, or closed from segments
A circumference can be pressed as one ring, or closed from separate arc segments. Which one applies is a drawing and an assembly question: a segmented circumference carries joints, and each joint has to be positioned and retained in the assembly. The arc segment page covers the segment itself; on a ring the first question is whether the part arrives as one piece at all.
Magnetization: axial, radial or multipole
Axial puts one pole on each end face, so the flux runs along the axis and the working faces are the flat ends. Radial puts one pole on the outside diameter and the other at the bore, so the flux crosses the wall and the working surfaces are the two cylindrical ones. Multipole patterns put alternating N and S sectors around the end face, around the outside diameter, around the bore, or around both, and are the arrangement used in sensor rotors and small motor rotors.
Each pattern is a fixture, and every pattern beyond a single two-pole pair also needs a datum: the pole positions are dimensioned from something, and that something belongs on the drawing. The pressed orientation is a separate commitment. For an anisotropic grade, the direction established while the part is formed has to serve the magnetization the circuit needs, so orientation and magnetization are settled together rather than one after the other. The magnetization directions and what sets each one are laid out separately.
Tolerances are agreed against the drawing
There is no single tolerance band for “ring”. What a part holds follows its own dimensions — the two diameters, the wall, the height — and the route it is made on. A thin-walled ring and a thick one on the same diameter do not hold the same band, so the band is agreed against the dimensions on the drawing rather than quoted for the shape. That is also why the drawing has to carry real dimensions and name the datum they are taken from.
Retention and delivery state
A permanent magnet is brittle, so how the ring is held in the assembly is part of the specification rather than an afterthought. A part that is bonded or potted, one that is clamped, and one that is retained by the fit alone are loaded differently, and the wall has to suit the way it is retained. Delivery state belongs here too: magnetized or supplied unmagnetized settles how the ring is handled on the line, and whether the field is applied with the assembly in place.
Material systems and routes
The material systems tooled in this geometry are listed further down this page, each with the routes it runs through. A route that is not listed for a shape says the route is not confirmed for it — not that the ring cannot be made. Ferrite rings are normally supplied uncoated; an NdFeB ring needs surface protection, and the exposure of the position decides which one.
What to send for a ring review
- Outside diameter, bore diameter and height, with the datum the dimensions are taken from.
- The magnetization — axial, diametric, radial or multipole — with N and S, and the pole count and pitch where the pattern is multipole.
- What the pole pattern is dimensioned from, when the pattern is multipole.
- How the ring is retained in the assembly, and the temperature it sees in service.
- Magnetized, or supplied unmagnetized.
Specification
What the Drawing Has to State
The dimensions a drawing has to settle before this part can be quoted, and what each one decides.
| Parameter | What the drawing states | What it decides |
|---|---|---|
| Outside diameter (OD) | Outside diameter, dimensioned from the datum the drawing names. | Sets the fit in the housing and the air gap to the surrounding pole piece. |
| Bore diameter (ID) | Bore diameter. | Sets the clearance to the shaft or core, and with the OD the radial wall. |
| Radial wall | The wall stated directly, or read as OD minus ID over two. | Carries the radial flux; a thin wall limits what the ring can give. |
| Height (axial) | Height along the axis. | Sets the pole area where the field crosses radially. |
| Multipole arrangement | End face, outer circumference or inner circumference, with the pole count and pitch. | Decides the fixture, and which surface is dimensioned. |
| Magnetic orientation | The direction established while the part is formed. | For an anisotropic grade, the pressed orientation has to serve the magnetization the circuit needs. |
| Delivery state | Magnetized, or supplied unmagnetized. | Settles handling, and whether the field is applied with the assembly in place. |
Tolerance is agreed against the dimensions on the drawing. A ring that carries a multipole pattern adds the fixture datum to the drawing, because the pole positions are dimensioned from it.
Material Systems
Materials Offering This Shape
Material systems tooled in this geometry, each with its own grade range and manufacturing route.
Material System
Neodymium (NdFeB) Rare Earth Magnets
Manufacturing Routes
How This Shape Is Made
The production routes this geometry is confirmed in. Only the routes confirmed for the shape are listed here, and a shape with none listed is not a statement that it cannot be made.
Applications
Explore Applications for the Related Materials
Explore application guidance for the materials listed above. Suitability of this geometry is evaluated against the specific assembly and operating requirements.
Project Evidence
Case Studies
Documented project records that reference the materials offering this shape.
Magnetization
Multipole Ring Configurations
A multipole ring can have alternating north and south poles on an end face, around the outer circumference or around the inner circumference. Ring describes the geometry; the working surface, pole count, pole pitch and field requirement define the magnetic configuration. Feasibility depends on the material grade, forming orientation, geometry and magnetizing fixture, and is confirmed for the project.
Multipole on an End Face
Principle illustrationAlternating north and south poles on an end face, the arrangement used in sensor rotors and small motor rotors.
Pattern details
- Direction
- Set by the pole pattern and the magnetizing fixture
- Pole pattern
- Multipole on an end face (four poles shown as an example)
- Poles sit on
- End face
Boundaries: The pole count and the pole pitch follow the tooling and the magnetic circuit; four poles are shown as an example, not as a range that is offered.
Multipole around the Outer Circumference
Principle illustrationAlternating north and south poles around the outer circumference of a ring or a cylinder.
Pattern details
- Direction
- Set by the pole pattern and the magnetizing fixture
- Pole pattern
- Multipole around the outer circumference (four poles shown as an example)
- Poles sit on
- Outer circumference
Boundaries: The pole count and the pole pitch follow the tooling and the magnetic circuit; four poles are shown as an example, not as a range that is offered.
Multipole around the Inner Circumference
Principle illustrationAlternating north and south poles around the inner circumference, at the bore of a ring.
Pattern details
- Direction
- Set by the pole pattern and the magnetizing fixture
- Pole pattern
- Multipole around the inner circumference (four poles shown as an example)
- Poles sit on
- Inner circumference
Boundaries: The pole count and the pole pitch follow the tooling and the magnetic circuit; four poles are shown as an example, not as a range that is offered.
Magnetization feasibility depends on the material, the manufacturing process, the geometry and the required pole pattern. Send us your drawing, sample or magnetization diagram for evaluation. For an assessment, send the ring dimensions, working surface, pole count and pole pattern, together with the required field or flux and the measurement position. If these are not yet defined, a drawing or sample is enough to begin the discussion.
Custom Tooling
Need a Custom Ring Magnet?
Send the 2D/3D drawing or the dimensional specification for this geometry. Tooling feasibility is assessed against the material system you intend to use, and we reply typically within 3 business days; the assessment itself takes as long as the drawing and the project require.