Block Sintered Hard Ferrite ceramic Block Bar Shape Magnets Y30bh

Wet Anisotropic, Dry Isotropic & Dry Anisotropic Hard Ferrite magnet

The molding of Ferrite Block Magnet is mostly by a press machine equipped with coil what can generate an external magnetic field for getting anisotropic magnet. The material for making anisotropic Hard Ferrite magnet is usually at wet slurry status so that molecules can be perfectly aligned in molding process. So we call magnets made by such kind process as wet anisotropic Hard Ferrite magnets what only can be magnetized along pre-orientation. The (BH)max of anisotropic Hard Ferrite is several times stronger than of isotropic Hard Ferrite magnet.

The raw material for making isotropic Ferrite Block Magnet is generally at dry powder status. The molding is by a punch machine what could not apply an external magnetic field on magnet. Thus the subsequently attained magnets are called dry isotropic Hard Ferrite magnets. Magnetization on isotropic Ferrite Block Magnet could be done with any preferred orientation and pattern depending on magnetizing yoke.

There is also one type Ferrite Block Magnet called dry anisotropic Hard Ferrite magnet. It is made of dry material powder but being oriented by an external magnetic field. The magnetic property of dry anisotropic Hard Ferrite magnet is lower than wet anisotropic one. Usually the dry and anisotropic process is used to mold magnet with complex structure but higher property than isotropic one.

Shape and Dimensional Tolerance

Ferrite Block Magnet can be economically molded with ring, arc segment, rectangular, disc, cylinder, trapezium or 2 combined geometries in one piece. Depending on these basic geometries, sphere, olivary shape, and other irregular geometry are available by further machining process. Slotting in Hard Ferrite magnet is practicable by pre-design in tooling or diamond grinding process. Hard Ferrite magnets with 3S (super-small, super-big and super-thin) structure are also producible by wet molding process.

The dimensional deviation of Hard Ferrite magnet is controlled within +/-2% before being machined, and could be controlled within +/-0.10mm after being simply ground by diamond tool. Customs tolerance or precise control even +/-0.015mm is achievable, but should be negotiated. In most circumstance, wet anisotropic Ferrite Block Magnet is supplied with surfaces which parallel to anisotropic orientation un-ground and other surfaces ground. Definitions on tolerance of concentricity, roundness, squareness, perpendicularity and others please refer to MMPA standard No. 0100-00 or DIN17410 or ISO2768.

Tooling of Hard Ferrite Magnet

The economic process for manufacturing Ferrite Block Magnet at big quantity is by molding with tooling. The tooling for making anisotropic Hard Ferrite magnet is considerably expensive, but for making isotropic Hard Ferrite magnet it is cheap. If the required magnet is with same diameter, or same length and width when it is block type, as the current tooling, then we can utilize the ready tooling to mold different thickness/height magnets within permissible range.

In practice, sometimes we slice big block, grind bigger diameter ring/disc and machine arc segment type of close dimension into the required one. This process is helpful to get precise dimension, to save tooling cost when the order quantity is not so big (particularly at prototype phase), and to homogenize weight and flux of each piece product. The shortage of making magnet by machine is very expensive cost.

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Typical Magnetic Performance for Hard Ferrite magnet

Physical property of Hard Ferrite magnets

USA Standard - Permanent Ferrite / Ceramic magnet

The Standard of International Electronics Committee (IEC404-8-1)