Injection Molded Magnets

Injection molded magnets, as a unique method of manufacturing permanent magnets, offer diverse magnet options for various fields and play an increasingly important role in modern industry.

Definition of Injection Molded Magnets

Injection molded magnets are produced by mixing magnetic powder, binders (such as PA6, PA12, PPS, etc.), and additives, and then using a specialized injection molding machine to manufacture the magnets through the injection molding process. This method combines the high magnetic properties of the magnetic powder with the excellent mechanical performance of the binder, providing a variety of features and advantages that can be tailored to meet customer specifications for magnetic, mechanical, and environmental requirements.

The performance of injection molded magnets mainly depends on the type of magnetic powder used, the binders, the filling ratio of the magnetic powder, and the molding process. The technical indicators for evaluating magnetic plastic include remanence, coercivity, intrinsic coercivity, and maximum magnetic energy product.

Types of Magnetic Powders Used in Injection Molded Magnets

| Neodymium Iron Boron (NdFeB) Powder: This type of magnetic powder has high residual magnetism, high coercivity, and high energy density, widely used in injection molded magnets requiring high performance.

| Samarium Cobalt (SmCo) Powder: Known for its excellent temperature stability and corrosion resistance, this powder is suitable for applications that require maintaining magnetic properties in high-temperature or corrosive environments.

| Ferrite Powder: Although this magnetic powder has average magnetic properties, it is commonly used due to its low cost.

Types of Binders for Injection Molded Magnets

| PA6: Provides high fluidity, moderate magnetic performance, and low cost.

| PA12: Offers high fluidity and moderate magnetic performance.

| PPS: Known for high heat resistance, high fluidity, and high magnetic performance.

Magnetization of Injection Molded Magnets

Based on whether an oriented magnetic field is applied during the manufacturing process, injection molded magnets can be categorized into isotropic and anisotropic types. Various magnetization methods can be employed, such as radial, axial, radial, multipolar, or localized magnetization.

Advantages of Injection Molded Magnets

| High Magnetic Performance: Utilizing high-performance rare earth magnetic powders allows injection-molded magnets to generate a strong magnetic field in a compact volume.

| Good Mechanical Properties: The addition of thermoplastics enhances the mechanical strength and toughness of injection-molded magnets, enabling them to withstand certain impacts and vibrations.

| High Customizability: The injection molding process allows for the easy creation of various complex shapes, and magnetic and physical properties can be tailored according to specific requirements for different applications.

| Wide Temperature Range: The binders and magnetic powders used can meet application temperatures from -40℃ to 180℃, ensuring stable performance across a wide range of temperature environments, suitable for various industrial and civilian sectors.

| Corrosion Resistance: The high content of polymer binders in injection molded magnets endows them with strong corrosion resistance, allowing for long-term use in harsh environments such as humidity and salt fog without damage.

Tech. Control of Injection Molded Magnets

| Injection Temperature: The injection temperature should be determined based on the nature of the binder, typically ranging from 150 to 250℃, ensuring the binder flows adequately for the uniform distribution of the magnetic powder and to avoid surface defects such as flow marks and bubbles.

| Injection Pressure: The injection pressure and speed should be moderate to prevent overflow or internal stress caused by excessive pressure or speed, which can affect the surface quality of the magnet.

| Dimensional Control: The dimensions of injection molded products align closely with the injection mold cavity, allowing for high dimensional accuracy. Additionally, the binder’s shrinkage during cooling results in dimension changes, which depend on the product’s thickness and shape.

How to Choose the Right Injection Molded Magnets

| Operating Temperature: The temperature range of the application environment is also a factor in choosing plastic magnets. The maximum operating temperature of injection molded magnets depends on the magnetic powder and binder used, for example, ferrite powder combined with nylon6 or PPS can withstand tests at 180℃, while nylon12 melts above 170℃.

| Magnetic Performance: This is a crucial indicator of magnet performance, including magnetic permeability, coercivity, and residual magnetism. Different applications require different magnetic performance levels, so it is essential to determine the required magnetic parameters based on specific needs.

| Cost: Cost is a factor that should be taken into account when selecting injection molded magnets. Different materials for injection molded magnets have different price points, so it is necessary to consider budget constraints when choosing materials.

Main Applications of Injection Molded Magnets

| Injection Molded Magnetic Tiles: They offer high magnetic efficiency, are not easily shattered, and can achieve low voltage start-up for micro motors requiring start-up voltage.

| Rotor Magnets: Mainly used in the rotors of DC brushless motors, such as those in air conditioners, household appliances, and synchronous motors, as well as magnetic couplers and other fields. These can be integrally molded with the shaft.