Sintered NDF,as a high-performance permanent magnet material, relies heavily on the optimized design of its magnetic circuit structure to fully realize its magnetic properties. Magnetic circuit design must revolve around core objectives such as magnetic field distribution, leakage flux control, and increased magnetic flux density. Through structural innovation and matching material properties, efficient utilization of magnetic energy can be achieved. The following analysis focuses on key dimensions of magnetic circuit structure design.
Basic Magnetic Circuit Construction: The construction of the basic magnetic circuit must focus on the precise control of the magnetic field direction and flux path. The strong magnetism of sintered ndfeb requires the magnetic circuit design to first clearly define the magnetic field direction. For example, in motor applications, a rotating multi-pole magnetic field must be formed on the rotor or stator surface through the arrangement of the poles of tile-shaped or arc-shaped magnets. This design uses magnetically conductive materials (such as silicon steel sheets) to construct a low-resistivity path, efficiently guiding the magnetic flux to the working air gap and reducing energy loss in the magnetic circuit. The core of the basic magnetic circuit lies in establishing a stable magnetic flux transmission channel, ensuring that the interaction force between the magnetic field direction and moving parts is maximized, thereby improving torque output or linear motion efficiency.
Multi-pole Magnetic Circuit Design:Multi-pole magnetic circuit design enhances local magnetic properties through the magnetic field concentration effect. Multi-pole magnetic circuits utilize the property of magnetic field lines preferentially selecting the nearest opposite pole to form a loop, concentrating the magnetic field on the magnet surface. For example, in sensor applications, multi-pole magnetization of a single magnet or a combination of multiple single-pole magnets can create a dense distribution of magnetic field lines on the surface, significantly enhancing the magnetic field gradient. This design excels in micro-pitch adsorption scenarios, such as in the VCM motor of a mobile phone camera, where ultra-thin ring magnets combined with radial magnetic guiding structures can achieve focusing control with an accuracy of ±50μm, while reducing interference from magnetic leakage to surrounding electronic components.
Haylbeck arrays achieve magnetic field enhancement through a self-shielding effect. A Haylbeck array is a near-ideal magnetic circuit structure; its special arrangement allows the magnetic field loop to circulate within the magnet, significantly reducing the magnetic field strength in non-working areas while enhancing the magnetic field in working areas. For example, a ring-shaped Haylbeck magnetic circuit design can achieve near 100% magnetic field shielding in non-working areas while increasing the magnetic flux density in the working area to more than 1.5 times that of traditional magnetic circuits. This structure offers significant advantages in scenarios requiring a strong, single-sided magnetic field, such as the impeller drive of a magnetically coupled pump. The magnetic field penetrates the sealed casing to drive the impeller's rotation, preventing liquid from seeping into the motor unit and reducing the risk of motor burnout.
Focused magnetic circuit design achieves localized magnetic field enhancement through a specific orientation. By optimizing the shape of the magnetic material or magnet, the focused magnetic circuit concentrates the magnetic field in a specific area. For example, in hard disk drive head drive systems, radially magnetized arc-shaped magnets combined with high-precision magnetic yokes can control the magnetic track positioning error within 0.01μm, ensuring data read/write stability. The core of focused magnetic circuits lies in precisely controlling the magnetic circuit orientation to improve the uniformity and intensity of the local magnetic field, meeting high-precision sensing or positioning requirements.
The application of magnetically permeable materials guides the magnetic field distribution through magnetoresistance optimization. Magnetically permeable materials (such as SUS430 and DT4) have low magnetoresistance characteristics, guiding magnetic flux flow along a predetermined path. In magnetic circuit design, embedding magnetically permeable materials between the magnet and the working area reduces magnetic leakage and enhances the magnetic flux density in the working air gap. For example, in permanent magnet motors, the stator core uses a laminated silicon steel sheet structure, which reduces eddy current losses and improves motor efficiency by guiding magnetic flux transmission efficiently through high permeability. The selection of magnetic materials must consider permeability, saturation flux density, and mechanical strength to meet the needs of different application scenarios.
Single-sided magnetic design achieves unidirectional magnetic field enhancement through shielding technology. Single-sided magnets concentrate the magnetic field on one side by adding a magnetic shielding layer to one side of the magnet. For example, in magnetic door locks, countersunk magnets or can-shaped magnets, through shielding design, increase the magnetic field strength on the adsorption surface by more than 50%, while preventing interference from the magnetic field on the other side to electronic equipment. The core of single-sided magnets lies in achieving unidirectional magnetic field concentration through the synergistic effect of the shielding layer and the magnet, meeting the special requirements of adsorption, fixation, and other scenarios.
Comprehensive optimization of magnetic circuit design requires balancing performance, cost, and reliability. In practical applications, magnetic circuit design must comprehensively consider material costs, processing difficulty, and the operating environment. For example, in marine environments, salvage magnets require IP68-rated encapsulation and nickel-copper-nickel plating to resist seawater corrosion; in polar cryogenic environments, UH-grade magnets with epoxy resin encapsulation are necessary to ensure stable performance at -40°C. Furthermore, introducing heavy rare earth elements (such as dysprosium and terbium) through grain boundary diffusion technology can increase coercivity by more than 40% without significantly reducing remanence, extending the magnet's lifespan in high-temperature environments. The ultimate goal of magnetic circuit design is to achieve optimal expression of the magnetic properties of sintered ndfeb through the integration of structural innovation and materials science.
