We supply custom 8-pole Neodymium ring magnets with alternating North and South zones instead of a single N/S pair. The poles can be arranged on the flat face (axial multi-pole). Or around the circumference (radial multi-pole), depending on your application. Axial multi-pole rings are used in rotary encoders and position sensors. As the ring rotates past a Hall sensor or magnetoresistive sensor, each pole creates a signal pulse. More poles = higher resolution per revolution. Common configurations are available: 4-pole, 8-pole, 12-pole, 16-pole. Radial multi-pole rings are used in brushless motors and magnetic couplings. Alternating poles around the outer or inner diameter interact with stator coils or a mating ring. Provide smoother torque transmission than 2-pole configurations and enabling compact motor designs. We produce these by assembling pre-magnetized wedge segments into a bonded ring assembly. For production volumes, we can magnetize a single sintered ring using a multi-pole magnetizing fixture. Provide your OD, ID, thickness, pole count, and orientation (axial or radial). Why 8 Poles? (The Performance Advantage) This section highlights why the customer wants this specific feature. 1. Enhanced Sensor Resolution: For rotary encoders and speed sensors, a standard 2-pole magnet only provides one wave cycle per revolution. The 8-Pole Benefit: – Generates 4 complete sine-wave cycles per revolution. – This allows Hall Effect sensors to detect speed and position with 4x the resolution of a standard magnet. 2. Concentrated Holding Force: The 8-Pole Benefit: – By alternating the poles on a single face, the magnetic flux path is shortened. – It travels from N to S closely across the surface). – This creates a “shallow but intense” magnetic field. – Ideal for holding firmly against thin steel sheets where standard magnets would bleed through. 3. Torque Transmission: The 8-Pole Benefit: – In magnetic couplings, an 8-pole driver allows for higher torque transfer and “stiffer” locking compared to a 2-pole system. Magnetization Patterns You must distinguish between the two types of 8-pole patterns. They are not interchangeable. Type A: Axial 8-Pole (Face Magnetized) Pattern: The flat circular face is divided into 8 “pizza slice” segments. Appearance: Looks like a standard ring, but a viewing film reveals the 8 sectors. Application: Rotary encoders, thin-wall holding, magnetic levitation stabilization. Type B: Radial 8-Pole (OD/ID Magnetized) Pattern: The poles are located on the Outer Diameter (OD) or Inner Diameter (ID). Application: Brushless DC Motors (rotors), magnetic pump couplings. Production Note: – True radial multi-pole sintering is expensive. – For cost-efficiency, we can also supply this as a “Bonded Neodymium” ring (isotropic) or an “Assembly of 8 Arc Segments”. Manufacturing Methods Producing an 8-pole pattern on Sintered Neodymium requires high-voltage pulse magnetization. Monolithic (Single Piece): – Use a specialized copper fixture to pulse the 8-pole pattern onto a solid ring. – Best for high volume. Segmented Assembly: – For large rings (e.g., >50mm), glue 8 separate arc segments onto a steel carrier. – Best for large prototypes or motors. Applications Rotary Encoders: Speed and direction sensing in robotics. Micro-Motors: Stepper motor rotors requiring specific step angles. Magnetic Catches: – Low-profile latches for tablets/cases. – Axial 8-pole holds strongly to the matching metal plate without damaging internal electronics. Couplings: Hermetically sealed pump drives. Ordering Guide: Critical Data To quote an 8-Pole ring, we need to know: 1). Dimensions: OD x ID x Thickness. 2). Orientation: Is the 8-pole pattern on the Face (Axial) or the Edge (Radial)? 3). Sensor Type: Are you using a latching Hall sensor (requires square wave) or a linear Hall sensor (requires sine wave)? 4). Reference Mark: Do you need a physical mark on the “Pole 1” start point?