This is a guide for advanced buyers.
Sintered NdFeB magnets are challenging to work with.
- Magnet manufacturers can’t easily shape them into special shapes.
- And they can break easily during processing.
This is particular true with the edges and corners of sintered neodymium magents.
Their defective rates can increase dramatically as the overall dimension increases.
To overcome these issues, custom magnet factories developed a method:
- They crush these magnets, mix them with glue, and then shape them using magnets.
This created bonded NdFeB magnets, which have become popular for several reasons:
- Affordability: Bonded NdFeB magnets are cost-effective.
- Precise Shapes: They can be made in custom shapes with high accuracy.
- Strength: These magnets are mechanically strong and less likely to break.
- Lightweight: They are also lightweight.
Because of these benefits, bonded NdFeB magnets are widely used in various industries.
Creating bonded NdFeB magnets involves four main molding processes:
- Calendering, injection molding, extrusion molding, and traditional molding.
Among these, calendering and injection molding are the most common methods used.
However, it’s important to note that bonded NdFeB magnets aren’t as strong as sintered NdFeB magnets when it comes to their magnetic properties.
- Because bonded NdFeB magnets typically have only about 80% of the theoretical density due to the significant amount of adhesive used in their production.
On the bright side, bonded NdFeB magnets are isotropic, meaning they have the same magnetic properties in all directions.
This characteristic makes them highly versatile, allowing for the creation of magnets with multiple poles or even countless poles across the entire magnet’s surface.
(It’s worth mentioning that bonded NdFeB can also be made into anisotropic magnets for specialized applications.)
Key Takeaways
Molding Processes: There are four main molding processes for bonded NdFeB magnets: calendering, injection molding, extrusion molding, and traditional molding. Calendering and injection molding are the most widely used methods.
Density Comparison: Bonded NdFeB magnets have a lower density compared to sintered NdFeB magnets. This is because they contain a significant amount of adhesive, which reduces their magnetic strength.
Isotropic Magnets: Bonded NdFeB magnets are isotropic, meaning they have consistent magnetic properties in all directions. This property allows for the convenient creation of magnets with multiple or even numerous poles across the entire magnet’s surface.
Anisotropic Option: While bonded NdFeB magnets are typically isotropic, they can also be produced in anisotropic forms for specialized applications where specific magnetic properties are required.
Hot-pressed NdFeB
Hot pressing NdFeB is a method to create magnets without adding heavy rare earth elements.
It can achieve similar magnetic properties to sintered NdFeB magnets. These magnets have high density, strong alignment of magnetic particles, good resistance to corrosion, and high coercivity (ability to resist demagnetization). However, they do not have strong mechanical properties.
One challenge with hot pressing NdFeB is the high processing cost due to patent restrictions, limiting mass production to just a few companies.
These magnets are typically ring-shaped due to the limitations of the manufacturing process, which somewhat restricts their applications. They are mainly used in automotive electric power steering (EPS) motors and other specific fields.
Hot pressing NdFeB magnets have impressive magnetic properties
- With a maximum radial magnetic energy product of 240~360 kJ/m3.
- They are oriented along the radial direction, ensuring uniform magnetic properties, resulting in quiet motor operation and smooth torque output.
- Additionally, they have excellent heat resistance, with an operating temperature range of 180°C to 200°C.
Key Takeaways
Alternative to Heavy Rare Earth Elements: Hot pressing NdFeB magnets offer an alternative to sintered NdFeB magnets by achieving similar magnetic properties without the need for heavy rare earth elements. This makes them more environmentally friendly.
Advantages: These magnets have several advantages, including high density, strong magnetic alignment, corrosion resistance, and high coercivity. They can perform well in demanding conditions.
Limited Production: Due to patent restrictions and high processing costs, the mass production of hot pressing NdFeB magnets is limited to only a few companies. This can affect their availability in the market.
Ring-Shaped: Hot pressing NdFeB magnets are typically ring-shaped due to manufacturing limitations. This limits their scope of application to certain fields, such as automotive electric power steering (EPS) motors.
Impressive Magnetic Properties: These magnets exhibit impressive radial magnetic energy product values, ranging from 240 to 360 kJ/m3. Their uniform radial magnetic properties contribute to quiet motor operation and smooth torque output.
High Heat Resistance: Hot pressing NdFeB magnets can withstand high temperatures, with an operational range of 180°C to 200°C. This heat resistance makes them suitable for applications where elevated temperatures are encountered.
Characteristics
1. Bonded NdFeB: These magnets are commonly used in applications like hard disk optical drive spindle motors and smaller micro motors due to their specific magnetic properties and molding process.
2. Sintered NdFeB: Sintered NdFeB magnets find their place in larger power drive motors and various other fields because of their distinct magnetic properties and manufacturing process.
3. Hot-Pressed NdFeB: These magnets are specialized and primarily used in automotive Electric Power Steering (EPS) systems, mainly due to their limited shape options.