Precision servo and permanent-magnet synchronous motors use NdFeB arc segments, bread-loaf profiles, or multipole rings to control the air-gap field and torque ripple. Mainrich supplies the rotor magnets, low-deviation encoder targets, or a finished rotor assembly, with grade and tolerance selected from the complete duty cycle.
Variations in radius, thickness, chord width, pole strength, and concentricity disturb the air-gap field. Servo programs therefore need matched dimensional and magnetic release criteria, not a generic magnet tolerance.
| Rotor topologies | SPM / IPM / multipole ring |
|---|---|
| Magnet profiles | Arc / bread-loaf / block / ring |
| Standard finishing | ±0.05 mm class |
| Precision grinding | ±0.02 mm class where supported |
| Flux matching | ±2% maximum per pole where specified |
| Temperature classes | SH / UH / EH for continuous duty |
| Encoder feedback | <±3° deviation, 100% inspected |
| Assembly option | Bonded, magnetized, mapped, and balanced |
Mainrich confirms ±0.02 mm class capability against the actual radius, thickness, width, coating, and measurement datum. Finished rotor delivery moves the bond gap, hub fit, magnetization, and balance into the same release plan. Mainrich engineers and quality-controls that release through a four-site production network in which it holds equity stakes.
Review finished rotor assembliesCompare broader DC and BLDC motor magnet paths, select from the N30 to N58 NdFeB production range, or review industrial automation applications.
Arc segments, bread-loaf profiles, and multipole rings solve different air-gap, tooling, cogging, and assembly problems. Mainrich reviews the rotor cross-section before the profile is released.
Precision-ground inner and outer radii control fit and air gap. Arc segments support prototype changes and a broad range of rotor diameters without committing the program to a one-piece ring tool.
A flat mounting face and curved pole face vary magnet thickness across the segment. That profile can move the air-gap field toward a more sinusoidal distribution and reduce cogging without a skewed stator.
A multipole ring replaces a bonded segment set and removes segment gaps from the rotor. It can simplify automated assembly where pole placement, concentricity, and repeatable field waveform justify the tooling path.
Continuous servo duty combines heat soak with peak-current demagnetizing fields. Grade selection follows the worst-case magnet temperature and load line, then adds margin below the material-class ceiling.
Dimensional fit, pole-to-pole flux, encoder field angle, and final rotor output are released against one control plan.
Supported geometries can be precision-ground to the ±0.02 mm class. Inspection follows the drawing datums for radius, thickness, chord width, and concentric features.
Rotor sets can be binned to a per-pole flux criterion. Sensor-grade encoder rings or discs with deviation below ±3° are 100% inspected after magnetization.
Coating and adhesive are selected together, then magnets are bonded to the hub or shaft. Magnetization, flux mapping, and dynamic balancing can be completed before shipment.
Review the finished assembly pathThese questions usually determine the final shape, grade, tolerance, feedback target, and assembly scope.
Arc segments are a flexible path for prototypes and medium-volume surface-mounted PMSM rotors. Bread-loaf profiles use a flat base and curved pole face to shape the air-gap field. Multipole rings improve concentricity and remove segment-bonding work, which can suit compact, higher-volume designs. The final choice follows the rotor geometry, cogging target, tooling plan, and annual volume.
Precision grinding to the ±0.02 mm class is supported on suitable geometries and dimensions. Standard finishing is typically ±0.05 mm. Critical radii, thickness, chord width, concentricity, and measurement method should be identified on the drawing so capability can be confirmed before tooling.
Select the class from peak magnet temperature, continuous duty cycle, peak-current demagnetizing field, cooling, and the motor load line. SH, UH, and EH classes have nominal ceilings of 150°C, 180°C, and 200°C, but those ceilings are not target rotor temperatures. The working design needs margin below the class limit.
Yes. Mainrich can supply sensor-grade ring, disc, or multipole target magnets for encoder feedback. Deviation below ±3 degrees is available with 100% post-magnetization inspection, provided the pole pattern, air gap, sensor position, and target field are defined.
Yes. Arc segments or a ring magnet can be bonded to the customer hub or shaft, with coating and adhesive selected together. Magnetization, flux mapping, dimensional release, and dynamic balancing can be included in the assembly control plan.
Send the rotor cross-section, peak temperature, duty cycle, pole count, tolerance targets, and annual volume. A human responds within 1 business day. Pricing follows within 2 business days.