Key takeaways
- Radial orientation is established during manufacture; magnetization defines the pole pattern and skew.
- The documented 10-pole N45SH radial specimen has a trapezoidal OD surface trace. The separate integrated Halbach sample has a sinusoidal trace.
- The November 2025 comparison used 10-pole Ø36.6 × Ø29.8 × 17 mm specimens: N45SH radial and integrated Halbach, and N50SH segmented. KCS-906A OD surface scans are historical sample evidence; probe standoff and uncertainty were not recorded, and the analyser result was marked not judged.
- OD probe scans do not establish air-gap field, motor torque ripple, efficiency or production-lot variation.
Overview
Overview
Radial rings remove adhesive joints between magnetic segments, but the ring still needs mounting, retention and inspection. Segmented designs have separate pole pieces and assembly joints. Neither construction guarantees a waveform or motor outcome; compare the full rotor, stator and control conditions.
Side-by-side
Side-by-Side Comparison
Reference properties and design questions. A count of comparison points does not establish a material or supplier recommendation.
| Criterion | Radial Multi-pole Ring | Arc Segment Assembly |
|---|---|---|
| Construction | One radially oriented sintered magnetic body | Separate magnets assembled around the rotor |
| Documented waveform | Trapezoidal OD scan on the 10-pole N45SH sample | Separate historical N50SH specimen; keep its test identity |
| Motor torque and efficiency | Requires matched motor tests | Requires matched motor tests |
| Production consistency | Requires a defined inspection plan and lot data | Requires a defined inspection plan and lot data |
| Assembly | No joints between magnetic segments; rotor mounting still required | Segment positioning, joints and retention required |
| Pole pattern | Confirm orientation and magnetization fixture | Confirm segment orientation and arrangement |
| Tooling and unit cost | Quote for the geometry and volume | Quote for the geometry and volume |
Confirm source conditions and the actual part requirements before using reference values as acceptance limits.
Use cases
Conditions for considering each option
When Radial Multi-pole Ring wins
- The specified one-piece ring meets the waveform and rotor fit requirements.
- Removing segment assembly joints benefits the validated production process.
When Arc Segment Assembly wins
- Separate pole pieces suit the rotor geometry or development changes.
- The qualified segment assembly meets performance and cost requirements.
How to choose
Decision Framework
Decision framework
Start with the required field waveform and rotor geometry. Compare complete motor results under matched conditions, then assess tooling, assembly, retention and inspection cost. There is no established universal torque-ripple percentage or monthly-volume crossover between these constructions.
Specs
Related NdFeB Grades
N42SH
150°C classN42SH reference: 40–43 MGOe at 20°C, with a nominal 150°C temperature class.
Reference; drawing review required
N45SH
150°C classN45SH reference: 43–46 MGOe at 20°C, with a nominal 150°C temperature class.
Reference; drawing review required
N48SH
150°C classN48SH reference: 45–48 MGOe at 20°C, with a nominal 150°C temperature class.
Reference; drawing review required
Industries
Related Applications
Robotics
NdFeB design inputs for robot joint motors, compact actuators and servo drives.
EV Motors
NdFeB magnet design inputs for permanent-magnet traction motors, auxiliary drives and e-axles.
Industrial Automation
NdFeB magnets for stepper motors, servo drives, linear actuators, magnetic couplings, and factory automation equipment across European and North American manufacturing.
Questions
Frequently Asked Questions
When should I use a radial ring instead of segments?
+
When the qualified ring and rotor assembly meet the motor requirements and production plan. The documented radial sample has a trapezoidal surface trace; choosing a radial ring does not guarantee sinusoidal air-gap flux or low torque ripple.
How much higher is torque ripple with arc segments?
+
The supplied surface scans do not measure torque ripple. Compare matched motors with defined stator, air gap, speed, load and controller settings before assigning a percentage difference.
Are radial rings more expensive than segments?
+
Compare quotes for tooling, magnet production, assembly and inspection at the intended volume. A one-piece ring removes joints between segments but still needs rotor assembly. No universal cost crossover is established.
Need help deciding?
Share your drawing, operating conditions and acceptance requirements for review. Human response within 1 business day.