Injection molded neodymium magnet

Injection molded neodymium magnets are a new types of composite material. It is mainly composed of neodymium-iron-boron magnetic powder,plastic (such as nylon,PPS,etc.), and a small amount of additives (such as lubricants, antioxidants, plasticizers,etc.). These materials are mixed through special processes and then molded into magnets through injection molding processes.

In the production of injection-molded neodymium magnets, the higher the content of magnetic powder, the stronger the magnetic properties of the magnets are usually. However, too high a content of magnetic powder may lead to a decrease in the mechanical properties of the magnets, making them fragile and brittle. Therefore, a balance between magnetic properties and mechanical properties is needed. Generally speaking, the content of magnetic powder may be between 70% and 90%, while the remaining part is plastic matrix and additives that account for no more than 1%.

The working temperature of injection molded neodymium magnets is relatively low, generally below 120℃. At high temperatures, the plastic substrate gradually softens, resulting in a decrease in the strength and stability of the entire magnet. Once the injection molded magnets deform due to high temperature softening, the magnetic properties of the magnets will be seriously affected.

In addition, high temperatures may also have a negative impact on the magnetic properties of neodymium iron boron magnetic powder. Although neodymium iron boron itself has a high Curie temperature, in practical applications, its working temperature range is limited due to its combination with the plastic substrate. If it is exposed to high temperatures for a long time, irreversible loss of magnetic properties will occur.

Injection molded neodymium magnets combine the high performance of NdFeB with the high efficiency and precision of injection molding. However, due to the low filler ratio of magnetic powder, the magnetic properties of injection molded neodymium magnets are usually lower than those of pressed neodymium magnet.

Advantages of injection molded neodymium magnets

Injection molded neodymium magnet
Injection molded neodymium magnets in various shapes

1. Smooth surface

A significant feature of injection molded neodymium magnets is their very smooth and delicate surface, which makes them attractive in appearance.

This not only improves the appearance quality of the product, but also reduces the need for subsequent processing. Traditional manufacturing processes often require additional polishing or plating steps to achieve the desired surface quality, while injection-molded neodymium magnets achieve this during the production process, greatly shortening the production cycle and reducing processing costs.

2. Extremely high dimensional accuracy

In addition to surface finish, injection molded neodymium magnets also have extremely high dimensional accuracy. This accuracy means that the product can meet the design specifications during production without requiring subsequent secondary processing. This is particularly important for components that require precise fit, such as micro-motors, sensors, and other high-precision devices, which have extremely tight dimensional tolerance requirements.

3. Complex shape

The advancement of injection molding technology enables magnets to achieve complex shapes, which provides engineers with unprecedented design freedom. This ability allows magnets to better adapt to specific application requirements, such as complex magnetic field distributions or special installation requirements. This design flexibility is a key factor that makes injection molded magnets stand out among many magnets.

4. Uniform magnetic field distribution

In the production process, the raw materials are evenly mixed to ensure that the magnetic powder is evenly distributed throughout the plastic matrix. After magnetization, these injection-molded neodymium magnets exhibit uniform magnetic field distribution characteristics. In precision sensors, motors, and magnetic coupling systems, a uniform magnetic field can ensure accurate control and efficient operation of the device.

5. Good corrosion resistance

The plastic substrate of injection molded neodymium magnets has good corrosion resistance and can isolate the internal magnetic powder from the external environment. Even without additional protective coatings, it has good corrosion resistance.

Manufacturing process of injection molded neodymium magnet

Manufacturing process

1.Raw material preparation: Firstly, neodymium-iron-boron magnetic powder, thermoplastic resin, and necessary additives need to be prepared. The selection and ratio of these raw materials are crucial to the magnetic and mechanical properties of the final product.

2.Premixing: Mixing neodymium-iron-boron magnetic powder, thermoplastic resin, and additives in a certain ratio. This step ensures that the magnetic powder is evenly dispersed in the resin, laying the foundation for subsequent injection molding.

3.Granulation: The mixed raw materials are made into plastic magnetic granules through a granulator. This process usually involves heating and cooling to form granular materials suitable for injection molding.

4.Injection molding: The plastic magnetic particles are injected into a pre-designed mold through an injection molding machine. The design of the mold shape usually depends on the desired final product shape. During the injection process, the molten mixture flows fully under high pressure and high temperature and comes into contact with the mold surface, which is quickly cooled through the mold’s cooling system to ensure the accuracy of the molding.

5.Cooling and demolding: Once the mixture has cooled and hardened, the mold is opened and the product is removed from the mold. This step requires precise control to avoid product deformation or breakage.

6.Magnetizing: According to customer requirements, magnetizing or maintaining a non-magnetic state is performed on the magnet after injection molding. Magnetizing is a key step in imparting specific magnetic properties to the magnet.

7.Quality inspection: The produced injection-molded neodymium-iron-boron magnets require strict quality inspection to ensure that their performance meets customer requirements. This includes testing the dimensions, shape, magnetic properties, and other aspects of the magnets.

The grade of injection molded neodymium magnet

GradeRemanence /BrCoercivity/HcbIntrinsic coercivity/HcjMaximum energy product/(BH)maxDensity
 mTGskA/mOekA/mOekJ/m3MGOeg/cm³
NB2535335302473098725911221.82.733.79
NB30L138138102563211671843124.63.094.21
NB4045545503003769697876034.74.364.52
NB5050350303254078647813241.95.264.91
NB7059259203704647681854956.77.135.34
NB8064764703844829589740165.48.225.67
NC1527627601952453679853113.61.713.52
NC2033633602352946656824119.72.483.86
NC30370370026633469431184024.53.084.07
NC30L38438402643310680854825.43.194.21
NC40H447447031239158991129534.54.344.61
NC50500500034042748771102342.15.295.02
NC60533533037246728991129049.56.215.11
HNB120a7867860461579086010800101.112.74.92
HNB140a8218210501629010031260011314.25.15

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