Product Descriptions
Compact Annular Power for Rotary Applications
For engineers designing rotating equipment that requires both a central shaft and high magnetic flux, the strong neodymium magnet ring offers an ideal solution. These annular sintered NdFeB magnets generate holding forces or driving torques comparable to solid discs but allow bolts, rods, or shafts to pass through the center. Typical applications include magnetic couplings (torque transmission through a sealed barrier), brushless DC motor rotors, rotary encoders, and permanent magnet grippers. Our strong neodymium magnet rings are manufactured from 100% virgin rare‑earth materials (purity ≥95%) with full vertical integration – from alloy melting to final magnetization. Grades range from N35 (economical) to N52 (maximum energy), with high‑temperature N42SH, N40UH, and N38EH options for environments up to 200°C. Precision ID/OD grinding achieves concentricity within ±0.03 mm and wall thickness uniformity of ±0.02 mm, critical for high‑speed rotation and consistent air gaps. Standard Ni‑Cu‑Ni triple plating (13‑18 μm) provides ≥72 hours salt spray resistance; epoxy or gold coatings are available for specialized needs. Custom sizes (OD from 5 mm to 150 mm, ID from 2 mm to 120 mm), multi‑pole magnetization patterns (2 to 48 poles), and axial or diametrical orientation are available for OEM projects.
Why a Ring Geometry Delivers Superior Mechanical Integration
Through‑Shaft Mounting
A strong neodymium magnet ring slides directly onto a shaft or bolt. This eliminates complex adhesive fixtures or external housings, simplifying assembly and reducing overall rotor inertia.
Multi‑Pole Magnetization
We magnetize rings with precise axial (through thickness) or diametrical patterns. Multi‑pole configurations (up to 48 poles) are available for encoder feedback and high‑resolution speed sensing.
High Torque Density
Concentrating magnetic material near the outer diameter where tangential force is highest allows a strong neodymium magnet ring to achieve excellent torque per unit weight, ideal for compact couplings and motors.
Technical Specifications – Strong Neodymium Magnet Rings
Below are typical magnetic properties and common ring geometries. Custom dimensions, grades, and magnetizations are available.
| Grade | Br (T) | Hcj (kA/m) | BHmax (kJ/m³) | Max Temp (°C) | Typical Applications |
|---|---|---|---|---|---|
| N42 (standard) | 1.30-1.32 | ≥955 (≥12 kOe) | 318-334 (40-42 MGOe) | 80 (176°F) | General magnetic couplings, motor rotors |
| N48 (high energy) | 1.38-1.42 | ≥955 (≥12 kOe) | 366-382 (46-48 MGOe) | 80 (176°F) | Compact, high‑torque designs |
| N52 (maximum energy) | 1.43-1.48 | ≥876 (≥11 kOe) | 398-414 (50-52 MGOe) | 70 (158°F) | Extreme miniaturization |
| N42SH (high temp) | 1.30-1.32 | ≥1590 (≥20 kOe) | 318-334 (40-42 MGOe) | 150 (302°F) | Automotive under‑hood, servos |
*Standard ring sizes (OD×ID×H, mm): 20×10×5, 25×12×6, 30×15×8, 40×20×10, 50×30×12, 60×40×15, 80×60×20. Custom sizes available.
Magnetic field direction
Coating / Plating
Neodymium ring shaped magnets require protective coatings to prevent corrosion. Common options include nickel plating (Ni-Cu-Ni), zinc, epoxy, and gold. These thin layers provide durability without compromising magnetic performance, ensuring longevity in various environments while maintaining the magnet's structural integrity and functional characteristics.
High-Precision Manufacturing
Neodymium magnets can maintain dimensional accuracy within ±0.05mm through advanced precision machining techniques including surface grinding and CNC cutting processes. This tight tolerance control ensures consistent performance in applications requiring precise magnetic field distribution and mechanical fit.
Magnetic Grade Parameters
Built on Vertical Integration – Consistent Quality You Can Rely On
Our factory controls every production step for strong neodymium magnet rings: vacuum induction melting using certified virgin rare earths (no recycled scrap), jet milling to fine powder, axial or radial pressing in a magnetic field, sintering in controlled‑atmosphere furnaces, solution heat treatment, precision ID/OD grinding, automated Ni‑Cu‑Ni electroplating, and final multi‑pole magnetization. Each ring is 100% inspected for magnetic flux (Helmholtz coil or Gauss array), dimensional accuracy (CMM or vision system), and coating thickness (XRF). Salt‑spray samples are tested per ASTM B117. All shipments include material test certificates with full traceability to raw material lots. Our IATF 16949 and ISO 9001 certifications guarantee consistent quality for automotive, industrial, and consumer OEMs.
Packaging & Logistics – Safe Delivery Worldwide
Each ring is placed in a dedicated foam cavity within an 8‑cell anti‑shock inner box to prevent edge chipping. Outer cartons are reinforced with corner guards and labeled "Strong Magnetic Field". Lead times: standard sizes 7‑10 days; custom rings 15‑20 days after drawing approval. Free samples available for qualified projects. Express shipping via DHL/FedEx or economical sea freight.
FAQ
Q: What defines a "strong" neodymium magnet ring compared to standard rings?
A: A strong ring typically uses grade N48–N52, with Br >1.42 T. Wall thickness is minimized to fit into compact assemblies while maintaining high flux. Strength also depends on magnetization direction: axial rings deliver higher pull force for face‑to‑face attraction than radially magnetized rings of same size.
Q: What are the two common magnetization directions for a neodymium ring magnet?
A: Axial magnetization (north on one flat face, south on the other) is standard for holding and coupling. Radial magnetization (north on OD, south on ID) is used in motors, sensors, and magnetic bearings. Radial rings require special fixtures and cost 30–50% more than axial.
Q: How do you prevent cracking when assembling a neodymium ring onto a steel shaft?
A: The strong attraction can slam the ring into the shaft, causing brittle fracture. Use a non‑magnetic pilot guide (e.g., brass or plastic), press slowly with an arbor press, or thermally shrink the ring (heat to 150°C) to expand ID before sliding onto the shaft.
Q: Why does a neodymium ring magnet have lower pull force than a disc of the same OD and thickness?
A: A ring has a hollow center, reducing the effective magnetic contact area. For axial magnetization, pull force scales roughly with the annulus area (π(OD²‑ID²)/4). A disc of the same OD can have 30–60% higher pull force, but the ring allows a shaft or cable to pass through.
Q: Can a strong neodymium ring be used as a magnetic encoder?
A: Yes, a radially magnetized multipole ring (alternating N/S poles around circumference) is common for rotary encoders. It requires precise pole pitch (e.g., 2 mm per pole‑pair) and low runout. Grades N42SH or N38EH are preferred for stable performance from –40°C to +150°C.