Multi Pole Neodymium Ring Magnets

Short Product Description

We are a professional permanent magnet manufacturer with over 30 years of experience in rare earth magnet production. Unlike standard ring magnets that carry a single north-south pole pair, this multi-pole neodymium ring magnet has multiple alternating N/S poles arranged uniformly around its circumference, producing a continuous cyclic magnetic field pattern during rotation. This configuration is essential for brushless DC (BLDC) motor rotors, magnetic encoders, and precision motion control systems where a single pole pair per revolution cannot provide sufficient resolution or smoothness. Available in pole counts from 4 to 72+ (custom to 192), with grades N35 to N48. Sintered and bonded NdFeB options available. Custom pole counts, magnetization directions, and tight tolerances offered upon request.

Technical Specifications

Parameter | Specification

Material | Sintered NdFeB / Bonded NdFeB
Grade Range | N35 / N38 / N40 / N42 / N45 / N48
Pole Count | 4 / 6 / 8 / 12 / 16 / 24 / 32 / 48 / 64 / 72; custom to 192+
Outer Diameter (OD) | 10mm to 100mm standard; custom available
Inner Diameter (ID) | Customizable to fit shaft or mounting hub
Thickness | 2mm to 30mm standard; custom available
Tolerance | ±0.1mm standard; ±0.05mm available for encoder-grade rings
Magnetization Direction | Radial (poles on OD surface), Axial (poles on end faces), or Custom
Pole Transition | Sharp or sinusoidal, depending on magnetization fixture design
Coating | Ni-Cu-Ni (standard), Zinc, Epoxy, Gold, Passivation
Max Working Temperature | N grade: 80°C; M: 100°C; H: 120°C; SH: 150°C
Remanence (Br) | 1.18–1.42 T (N35–N48, sintered)
Density | 7.5 g/cm³ (sintered); 5.0–6.0 g/cm³ (bonded)

Product Features and Advantages

Multiple Pole Pairs Per Revolution – A multi-pole ring replaces a complex assembly of individual arc magnets with a single monolithic component. An 8-pole ring produces four complete N-S field cycles per revolution, generating a higher-resolution position signal than a standard single-pair ring and enabling smoother electronic commutation in BLDC motors.

Uniform Field Distribution Around Circumference – Because the poles are magnetized into a single continuous ring, pole spacing and alignment are inherently more consistent than assembling separate segments. This uniformity reduces torque ripple and improves encoder signal linearity.

Radial vs. Axial Multi-Pole Magnetization – Radial multi-pole magnetization places alternating poles on the outer cylindrical surface, the standard choice for BLDC motor rotors and side-reading encoders. Axial multi-pole magnetization places poles on the flat end face, preferred for compact axial-flux sensors and thin encoder discs. Specifying the wrong direction is the most common error; our engineering team confirms the correct pattern based on your sensor or stator geometry.

Two-Pulse Magnetization for Sharp Pole Edges – For high-performance BLDC rotors, we use a two-pulse magnetization process that achieves higher magnetization steepness at pole edges, resulting in higher overall rotor magnetization and reduced torque ripple compared to single-pulse magnetization.

Sintered vs. Bonded Material Selection – Sintered NdFeB multi-pole rings offer maximum magnetic strength and are the preferred choice for high-torque motors and high-resolution encoders. Bonded NdFeB rings provide higher dimensional precision, better pole-width consistency, and lower tooling cost, making them suitable for cost-sensitive applications such as fan motors, toy motors, and high-pole-count encoder rings where dimensional accuracy matters more than absolute magnetic strength.

Not a Standard Ring Magnet – A standard ring magnet has one N pole on one face and one S pole on the opposite face (axial) or one N and one S on opposite sides (diametrical). A multi-pole ring magnet has multiple alternating poles around a single surface. The two are not interchangeable. If your design requires a cyclic signal per revolution, a standard ring will not work. This distinction is critical for correct specification.

Application Scenarios

Brushless DC (BLDC) Motor Rotors – Multi-pole NdFeB rings are the core component of BLDC motor rotors in electric vehicle drive motors, e-bike hub motors, power tools, and industrial servo motors. The alternating pole pattern on the rotor surface interacts with the stator windings to produce smooth rotation with reduced cogging torque.

Magnetic Encoders – Incremental and absolute magnetic encoders use multi-pole rings to generate a high-resolution position signal. An encoder ring with 64 or 128 poles provides angular resolution far beyond what a single-pole-pair magnet can achieve. Typical encoder rings use bonded ferrite or bonded NdFeB with pole counts from 32 to 192, mounted on a shaft with a magnetic sensor IC positioned radially.

Automotive Auxiliary Motors – Electric seat adjusters, air conditioning compressor motors, and electric power steering (EPS) rotors increasingly use multi-pole ring magnets for their compact size, high torque density, and ability to withstand under-hood temperatures.

Industrial Automation & Robotics – CNC machine tool servo motors and robotic arm joint motors rely on multi-pole ring magnets for precise position feedback and stable torque output. The uniform pole distribution contributes directly to the sub-millimeter positioning accuracy required in automated production lines.

Water Pump & Fan Motors – Radial multi-pole rings are widely used in water pump rotors and cooling fan motors where a compact, integrated rotor magnet simplifies assembly and improves magnetic circuit efficiency.

Quality Assurance and Certifications

Certifications include IATF 16949 (automotive quality management), ISO 9001, ISO 14001, and ISO 45001. Compliance with RoHS, REACH, and CP65. 100% inspection on dimensions, magnetic properties, and coating adhesion. For multi-pole rings, we offer pole position verification to confirm pole count, pole spacing uniformity, and magnetization direction against specification. Full traceability from raw material to finished product. Packaging uses anti-magnetic shielding, foam protection, and export-grade cartons. For high-pole-count rings, we recommend protective fixtures during transit to prevent pole damage.

Customization Services

We offer full customization on Pole Count – 4 to 192 poles, with pole pairs calculated as total poles divided by two. Magnetization Direction – Radial (OD surface poles), Axial (end face poles), or custom. Material – Sintered NdFeB (N35–N48) for maximum strength, or Bonded NdFeB for higher dimensional precision and lower tooling cost. Size – OD, ID, and thickness tailored to your shaft and housing. Pole Transition – Sharp or sinusoidal, optimized for your sensor type. Coating – Ni-Cu-Ni, Zinc, Epoxy, Gold, or Passivation. Tolerance – ±0.1mm standard; ±0.05mm for encoder-grade rings.

Critical Design Note: Multi-pole magnetization requires a dedicated magnetizing fixture with one pole head per pole position. Fixture cost increases significantly with pole count and ring diameter. For sintered rings, the fixture must be designed for the specific ring dimensions and pole pattern; for bonded rings, the magnetization can often be performed after molding with a reusable ring-type multi-pole coil. This tooling cost should be factored into new project development and is non-recurring once the fixture is built.

Sample Policy: Sintered custom samples available within 10–15 working days. Bonded samples available within 5–7 working days. Free samples for qualified motor and encoder projects.

Why Choose Us

We have over 30 years of experience in rare earth magnet production. Our engineering team understands the practical difference between radial and axial multi-pole magnetization, and can recommend the correct pattern based on your motor topology or sensor mounting position. We offer both sintered and bonded material options, allowing you to balance magnetic strength against dimensional precision and tooling cost. For high-performance BLDC rotors, we apply two-pulse magnetization to achieve sharp pole edges and high magnetization uniformity. Long-term supplier to Fortune 500 companies including General Motors, Ford, Samsung, and Xiaomi. 24-hour quote and technical support.

Frequently Asked Questions

How do I choose between radial and axial multi-pole magnetization? Radial (poles on the outer cylindrical surface) is the standard choice for BLDC motor rotors and encoders where the sensor reads from the side. Axial (poles on the flat end face) is used for compact axial-flux sensors and thin encoder discs. The choice depends entirely on where your sensor or stator is positioned relative to the ring.

What pole count should I specify for a BLDC motor rotor? Pole count depends on your motor design and target speed. Lower pole counts (4–8) are common for high-speed motors; higher pole counts (12–24) suit low-speed, high-torque applications. Your motor designer will typically specify the required pole count based on stator slot count and desired electrical frequency.

What is the difference between multi-pole ring and standard ring magnet? A standard ring has one N and one S pole. A multi-pole ring has multiple alternating N/S poles around its circumference, producing multiple field cycles per revolution. They are not interchangeable.

Can you produce sintered and bonded multi-pole rings? Yes. Sintered offers maximum magnetic strength. Bonded offers higher dimensional precision, better pole-width consistency, and lower tooling cost. We recommend bonded for high-pole-count encoder rings and cost-sensitive motor applications.

What is the maximum pole count available? Standard production supports up to 72 poles for sintered rings. Bonded rings can be magnetized with up to several hundred poles, limited by the resolution of the magnetization fixture.

Is the magnetization fixture cost included in the unit price? No. Multi-pole magnetization requires a dedicated fixture. The fixture is a one-time tooling cost charged separately and is non-recurring. Once built, the fixture is reused for all subsequent orders of the same ring dimensions and pole pattern.

What is the delivery time? Bonded standard samples: 5–7 working days. Sintered custom samples: 10–15 working days. Production orders: 15–25 working days depending on pole count and material.

What is the minimum order quantity? MOQ varies by size, material, and pole count. Contact us for details.

Contact Us

Get a Quote Today! Email: zb16@magnets-world.com. Phone/WhatsApp: +86 18119636123. Address: Room 201, No.15, Longxinli, Siming District, Xiamen, Fujian, China. We reply within 24 hours.