Diametrically magnetized ring magnets

Unlike standard axial magnetization where poles are on the flat faces, diametrical magnetization places the North and South poles on the opposite curved sides of the ring. This is critical for applications like magnetic sensors, encoders, and brushless motors. When sourcing, you must specify the magnetic orientation clearly to avoid functional failure in your assembly.

For maximum magnetic strength, Neodymium (NdFeB) grades such as N35 to N52 are standard. However, if your application involves high temperatures, you must select grades with higher temperature resistance like SH, UH, or EH, which can withstand up to 200°C. For corrosive environments, Samarium Cobalt (SmCo) is a superior, albeit more expensive, alternative due to its excellent thermal stability and oxidation resistance.

Since Neodymium is highly prone to oxidation, a robust coating is mandatory. The industry standard is Ni-Cu-Ni (Nickel-Copper-Nickel) plating, which should pass a 24 to 48-hour Salt Spray Test. For medical or high-moisture environments, consider Epoxy coating or Parylene, as they provide a hermetic seal and better chemical resistance.

Buyers should request a Magnetic Flux Density report and a Hysteresis Curve (Demagnetization Curve). For diametrical rings used in sensors, the angle of magnetization deviation should be strictly controlled, typically within +/- 1 to 3 degrees, to ensure signal accuracy in the end product.

Magnets are classified as Dangerous Goods (Class 9) for air freight if they exceed certain magnetic field strengths. You must ensure the supplier provides Magnetic Shielding Packaging (using iron sheets) and a Non-Magnetic Inspection Report from a recognized body like DGM. Failure to do so can lead to seizure by customs or airlines.

Incorporate a Milestone Payment structure where the final 30-50% is paid only after a Pre-shipment Inspection (PSI). Use platforms like Made-in-China.com to identify Audited Suppliers who can provide ISO 9001 and IATF 16949 certifications, ensuring the factory has a rigorous Quality Management System for high-precision components.

The most common error is ambiguity in tolerances. For ring magnets, specify tolerances for Outer Diameter (OD), Inner Diameter (ID), and Thickness (e.g., +/- 0.05mm). Always provide a technical drawing indicating the magnetization direction with an arrow to prevent the supplier from producing axially magnetized rings by mistake.

Prices of NdFeB magnets are highly sensitive to Rare Earth element market fluctuations (Praseodymium-Neodymium prices). It is advisable to sign short-term price agreements or include a price adjustment clause based on a public index to mitigate the risk of sudden raw material cost spikes during long-term contracts.