We supply precision 8-Pole Axial Neodymium Rings (Face Multi-Pole).
The entire top face of standard ring magnets is North and the bottom is South.
But these specialized magnets feature 8 alternating poles (4N / 4S) distributed radially across the flat surface.
This “Surface Magnetization” configuration creates a dense, shallow magnetic circuit.
These loops are directly across the face of the ring.
This geometry is the industry standard for Rotary Encoders, Speed Sensors, and high-efficiency Magnetic Couplings.
Their the magnetic field must interact with a sensor or steel plate parallel to the magnet’s face.
The Engineering Logic: Why “Surface” Magnetization?
Explain the physics. Why do they want this weird pattern?
1. Sensor Resolution (4 Pulses per Rev):
The Application:
– Rotary speed detection.
The Function:
– As the ring rotates, a Hall Effect sensor placed near the surface detects 4 distinct North-South cycles per revolution.
The Benefit:
– This provides 4x the data resolution of a standard 2-pole magnet.
– Such feature allows for precise speed and position control in robotics and motor feedback systems.
2. Superior Holding on Thin Steel:
The Application:
– Magnetic latches on thin sheet metal.
The Physics:
– Standard magnets shoot their field deep into space.
– Multi-pole magnets loop their field tightly between the N and S sectors on the face.
The Benefit:
– This concentrates 100% of the magnetic energy right at the surface.
– And it provides exceptionally strong holding force on thin steel sheets (where standard magnets would “bleed” through and lose grip).
Manufacturing & Tooling
Pulse Magnetization:
– Creating this pattern on Sintered Neodymium requires a specialized High-Voltage Magnetizing Fixture (Coil).
Standard Sizes:
– We often have existing fixtures for common ODs (e.g., 20mm, 30mm), saving you tooling costs.
Custom Sizes:
– For unique dimensions, a one-time fixture fee may apply to build the custom coil.
Applications
Rotary Encoders: Volume knobs, robot joints, and control dials.
Brushless DC (BLDC) Motors: Axial flux pancake motors.
Magnetic Couplings: Driving a mixer or pump through a flat plastic wall.
Smart Accessories: Tablet case attachments (the tight field doesn’t damage internal electronics).
Ordering Guide: Critical Data
To quote this item, we need to know:
1). Dimensions: OD x ID x Thickness.
2). Sensor Match: Are you using this with a specific Hall Sensor chip? (Knowing the “Operating Gap” helps us verify the strength).
3). Reference Mark: Do you need a physical mark (laser dot or notch) to indicate the “Zero Position” (Start of Pole 1)?
4). Back-Iron: Will this be glued to a steel shaft? (This boosts the performance).
