Bonded magnet appeared around the 1970s, when the SmCo magnets have reached the commercialization. The market situation of sintered permanent magnet is very good, but it is difficult to be machined into special shape, and also prone to cracking and breakage, in the process of falling edge off angle and other issues,  also not easy to be assembled, thus the applications were limited. In order to solve this problem, the permanent magnet is crushed, mixed with plastic, and pressed in the magnetic field. This is probably the most original method of manufacturing bonded magnets.

Bonded NdFeB, consisting of Nd2Fe14B, is a kind of synthetic magnet. Bonded NdFeB magnets（also called as bonded neodymium magnets） are widely used because of their low cost, high dimensional accuracy, large form freedom, good mechanical strength and light weight. The annual growth rate is 35%. Since the emergence of NdFeB permanent magnet powder, the flexible bonded magnets have been developed rapidly due to their high magnetic properties.

Bonded NdFeB magnets processed by composing of magnetic powder, mixing, granulating, pressing, curing, finishing, coating, magnetic and packaging production process.The bonded NdFeB magnets can be made in diameter to multipole, radial, multi angle oblique filling, magnetizing axial multipolar etc. And can be machined into various complex shaped products, fine, super Pu, one-time high control precision. The energy product is three times of sintered ferrite magnets, coercivity and high magnetic properties, stability, consistency and good performance. The performance fluctuation in the range of 5%, the maximum working temperature can reach 150 degrees. The product surface coated with epoxy resin and parylene coating, corrosion resistance good, smooth, no bubbles, cracks, spalling Fly away, side, grain and other phenomena.

The advantages of bonded NdFeB magnets: high remanence, high coercivity, high magnetic energy products, high-performance price ratio, easy processing of various sizes and tiny size. Compared with sintered NdFeB magnets, it can be formed at one time without the second processing. It can be made into a magnet of various shapes, which is not comparable to a sintered magnet. By using bonded NdFeB magnets, the volume and weight of the motor can be greatly reduced.

PRODUCTION CAPABILITIES OF INJECTION MOLDED -BONDED MAGNETS

Bonded vs. sintered

Bonded

• Excellent geometric tolerances with minimal or no secondary operations
• Good mechanical properties
• Complex shapes
• Insert/overmolding of sub assemblies
• Higher electrical resistivity
• Multipole magnetization
• Tailored flux output for given size/shape magnet

Sintered

• Highest flux output
• Higher operating temperature

Bonded Magnets, (Polymer bonded magnets, Compression Bonded Neodymium Magnets, Injection Molded Ndfeb or Ferrite Magnets

Bonded Magnet (Polymer bonded magnets) is 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.

Bonded NdFeB magnet is composed with compression NdFeB magnet, injection NdFeB magnet and flexible NdFeB magnet. Since its birth in the middle of 1980’s, the demand of bonded NdFeB magnet has been dramatically increasing for the industries of automatic control, automobile, 3C products (computer, communication & consumer electronics) and household electric appliance with virtues as follows:

• Offering new and cost-effective solutions for design and manufacture with availabilities of typical toughness of plastic, diverse and complex geometry, preferred magnetizing pattern, as well as more assembling methods.
• Extensive choice of property range 1.0—11.5 MGOe.
• Much better resistance of corrosion than sintered NdFeB magnet.
• Free-machining by direct molding with net shape and close-tolerance
• Minimizing figure and weight of application due to its comparatively stronger magnetic property and lower density.

Bonded magnet materials can be made from Ceramic, NdFeB, or SmCo powders which are combined with a variety of plastic binders (Matrix). They can be either Injection Molded or Compression Bonded into complex magnet shapes with finished dimensions. Bonded magnet materials have a moderate resistance to corrosion and a low tolerance to heat because of the binder material. Bonded magnet materials are commonly used in automotive parts because they lend themselves to large production quantities and complex shape can be produced at a low cost.

Injection molded magnets can be formed into complex shapes and be insert molded directly onto other components to produce assembly parts. Compression bonded magnets offer higher magnetic output than injection-molded magnets, but are limited to more simple geometries.

Forming methods of Bonded Magnets

Bonded Magnets are formed by either injection molding or compression molding.

Injection molding provides flexible shapes and compression molding provides higher magnetic properties.

Injection Molded:

• Binder Types / Nylon / PPS / Polyamide.
• Temperature Range -40c – 180c
• Very Tight tolerances off tool ( 0.002 -0.003 Typical )
• Very good mechanical strength

Compression Bonded:

• Higher Magnetic Strength due to higher magnetic particle density.
• Epoxy Binder / Resistant to normal industrial solvents and automotive fluids
• Epoxy Coat after manufacturing to prevent oxidation
• Temperature Range -40c – 165c
• “Tight” tolerances off tool
• Good mechanical strength

Typical Bonded Magnet Applications:

• Sensors
• Brushless DC Motors

General Bonded Magnet Applications:

• Materials are isotropic and can be magnetized in any direction
• Wide range of existing tool sizes are available in rings, discs and rectangles
• Exsisting Multipole magnetizing fixtures for quick prototyping
• Easily machined
• Existing Multipole rings simplify assembly verse arc sepments

Surface Treatment:

In blending process, NdFeB alloy powder is embedded in epoxy resin or other thermal plastics what are solvent resistant against normal industrial and automotive fluids. Therefore bonded NdFeB magnet is more stable than sintered NdFeB magnet. However if the magnet is working in hot, moist and other corrosive environment, then coating is very necessary. Normally compression NdFeB magnet should have surface treated for protection purpose, meanwhile injection and calender bonded NdFeB magnet are no need to be coated due to high volume fraction of binder.

Temperature Character:

Both magnet remanence and coercive force will be decreased when the temperature on bonded NdFeB magnet is increased. Irreversible and reversible flux loss will take place at the same time. Temperature change will also obviously take effect on swelling, shrinkage, hardness, strength etc physical characters of bonded NdFeB magnet. As a composite, the maximum working temperature of bonded NdFeB magnet is not merely determined by the type of NdFeB alloy powder but also influenced by the used binder. The recommended working temperature of nylon 12 (PA12), nylon 6 (PA6), epoxy resin and PPS are respectively up to 100℃, 120℃, 180℃, 200℃ for continuously working.

The mix of carbon with metal powder and a binder is treated through multiple stages of kneading, pulverizing, sieving, mixing, moulding, heat treatment, graphitizing and finishing, to yield a high-quality hard carbon brush.

 TAS (Torque & Angle Sensor),

SAS(Steering Angle Sensor),

Seat adjustment  Motor,

ACV (Air Control Valve),

EGR (Exhaust Gas Recirculation)

Valve, VSAV (Variable Swirl Control Actuator),

Seat Belt Sensor,

Robot Position Sensor

Motor for home appliances, power tools and other industial applications

Our injection-molded magnets offer tremendous design versatility allowing engineers to add unique features to the magnet or magnet assembly that cannot be easily obtained using ceramic or sintered magnets. Injection-molded magnets are far less brittle, offer tighter tolerances, and meet magnetic requirements to a tighter tolerance. The injection-molding process can hold tolerances down to +/- .0005″ (.01mm). With this in mind, you can easily see that tighter air gaps, precision press fits, and intricate details can be achieved with great success.

Design features may be assembly keys, mechanical features, reduced part weight and size, inserts, and unique magnet geometry. You may also utilize the option to add a second or even third injection molding process to capture multiple design requirements in one magnetic solution!

Our experience incorporating two or three components in one molded assembly can represent tremendous cost savings. Using fabricated steel inserts is a cost-effective way of eliminating steps in the manufacturing process. Incorporating inserts in bonded-magnet design produces a product that has exceptional uniformity and functionality. Engineered thermoplastics are also an excellent choice as an alternative to steel inserts, offering the opportunity to add structural ribs, fine threads, and color-coding. Many binder systems can be used when injection molding magnets. Typically a nylon 6 or nylon 12 is used. Other options include PPS, EEA, or heat-resistant polyamides. When optimizing a second or third operation in the molding process, there is a very wide range of thermoplastics available to meet specific requirements.

It is a mixture of resin (PA6, PA 12, PSS) & the Ferrite magnetic powder, after mix together wit the additive, injective produced the magnet is called the Injection Ferrite magnet.

The magnetic power of the Injection Ferrite Magnet is comparatively lower than the Injection NdFeB Magnet, but the price is comparatively lower, this is best fits for the sensor magnetic rings, the micro motor that have complex shape and comparatively lower speed requirements.

Bonded permanent magnets: press molding, injection molding and heat pressing are the main manufacturing processes by which bonding.

• Bonded Ferrite magnets
• Bonded NdFeB magnets
• Bonded SmCo magnets

Our wide range of Injection Bonded Ferrite Magnets is known for its high durability and utility. We also offer customized solutions for these injection molded ferrite magnets to our customer’s benefit.