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Bonded Magnets


Allstar Magnetics has available Neodymium (NdFeB) Bonded Magnets. Bonded magnets are one of the most important magnetic materials. It opened a new world of application possibilities. Thermo-elastomer and thermo-plastic resins can be blended together with a variety of magnetic powders to form injection molded, compression and flexible magnets.

The bonded Ceramic materials are typically anisotropic and manufactured by using "binders" such as epoxy resins to hold the powder in place, rather than "sintering" the alloy. Energy products of the bonded neo magnet range from 5 MGOe to 15.1 MGOe. 

Bonded neo powder is produced by processing specific combination of elements that result in distinct magnetic and physical characteristics. These powders are the primary material used in the manufacture of bonded rare earth permanent magnets, which, in turn, are used in motors and sensors utilized in a wide variety of products for consumer and industrial end markets. Neodymium metal, one of the rare earth elements, is the primary raw material in neo powder. It is alloyed with iron and boron, occasionally along with other elements in small quantities (such as cobalt). The alloy is melted and then rapidly solidified by melt spinning to produce neo powders with the desired characteristics for the manufacture of bonded neo magnets.


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Bonded Magnets by Allstar Magnetics


Nd-Fe-B powder is combined with synthetic resin or polymer to form the bonded magnets. An important way of manufacturing these magnets is through the process of injection molding. The Nd-Fe-B alloy used for the production process is formed by a rapid quenching method. The hot molten Nd-Fe-B alloy is forced through a tiny nozzle unto a water cooling drum that is rotating at a very high speed to form thin crystalline Nd-Fe-B alloy ribbons that will be crushed into powder. The powder is further subjected to heat treatment to improve its coercive force and then mixed with the synthetic resin. The resulting mixture is kneaded, pelletized and then sent to the injection molding process. A mold which will form the desired shape of the magnet is first custom designed from a metal and the pellets are fed into the mold and melted at high pressure. Mechanical or hydraulic pressure is applied to the mixture so as to ensure that all cavities within the mold are filled. An external magnetic field (for anisotropic magnets) is also applied on the magnet during the injection molding process. It is then allowed to cool and removed with ejecting pins. Excess materials on the finished magnet is trimmed off and recycled. The finished magnet is inspected and packed up.


Bonded neo powder is incorporated into numerous end market applications that utilize bonded neo magnets. These products are primarily motors and sensors used in a range of products, including computer and office equipment (e.g., hard disk drives and optical disk drive motors and fax, copier and printer stepper motors), consumer electronics (e.g., personal video recorders and mp3 music players), automotive and industrial applications (e.g., instrument panel motors, seat motors and air bag sensors) and home ventilation systems (e.g., ceiling fans).


● MQP products are isotropic magnetic powders that are used in the manufacture of bonded magnets. No alignment field is necessary during the magnet manufacturing process for MQP-based magnets.
● MQP powder properties range:
     Br = 730 mT - 1000mT (7.30kG -10.00kG)
    (BH)max = 97kJ/m3 - 140kJ/m3 (12.2MGOe to 17.6 MGOe)
     Hci = 525kA/m - 1350kA/m (6.5kOe - 17.0kOe)
● MQA are anisotropic magnetic powders that are used in the manufacture of bonded magnets. An alignment field is necessary during the magnet manufacturing process to provide the anisotropy that yields higher magnetic properties.
● MQFP technology, applicable to all MQP grades, reduces the mean powder particle size from 160 to 5 micrometres.
● MQU are the highest-performing isotropic powders to be used in the production of MQ2-type magnets, which are fully dense isotropic magnets.


Injection molded magnets are available using ferrite, neodymium-iron-boron, or blends of magnetic materials to achieve an extensive range of properties. Binder types include Nylon 6 and 12, PPS, and Polyamide. The binders and magnetic alloys are capable of a wide range of application temperatures from below -40°C to above 180°C. The Injection molding process is particularly well suited to molding very intricate shapes and thin walled parts. The finished parts can be either very simple or complex in geometry. Magnetic materials can be insert injection molded directly inside or against an existing component to produce assembly pieces. Injection molded magnets dimensionally conform to mold cavities, which are precisely machined, resulting in finished products which usually do not require further finishing operations. This eliminates subsequent operations and reduces total cost.


Compression bonded magnets are available using many isotropic neodymium iron boron material grades as well as crushed & powdered samarium cobalt materials. Combinations of different material grades may also be used to create specific magnetic characteristics. Compression bonded magnets offers higher magnetic strength than injection molded magnets due to their higher magnetic particle density, but are limited to simpler geometries. The epoxy binder used is resistant to normal industrial solvent and automotive fluids. To reduce corrosion of the rare earth magnetic materials, they are further coated with epoxy after shaping. The normal application temperatures range from below -40°C to above 165°C. Compression bonding is most appropriate for relatively simple geometries due to limitations of the compaction process. The tooling costs for compression bonding is comparatively low, making it a better choice than injection molding where volumes are small. However, with modest automation, compression bonding can also be adopted for high volume manufacturing, with volumes upto millions of pieces per year.