SMZR 25x175 / N52 - magnetic separator with handle

Strengths and weaknesses of rare earth magnets.

Besides their stability, neodymium magnets are valued for these benefits:

• They retain magnetic properties for almost ten years – the loss is just ~1% (based on simulations),
• Magnets very well resist against loss of magnetization caused by ambient magnetic noise,
• A magnet with a smooth nickel surface has better aesthetics,
• They feature high magnetic induction at the operating surface, which improves attraction properties,
• Due to their durability and thermal resistance, neodymium magnets are capable of operate (depending on the shape) even at high temperatures reaching 230°C or more...
• In view of the option of accurate shaping and customization to specialized requirements, magnetic components can be created in a wide range of shapes and sizes, which makes them more universal,
• Fundamental importance in high-tech industry – they are commonly used in mass storage devices, electric motors, medical devices, as well as other advanced devices.
• Compactness – despite small sizes they generate large force, making them ideal for precision applications

What to avoid - cons of neodymium magnets and proposals for their use:

• Susceptibility to cracking is one of their disadvantages. Upon strong impact they can break. We advise keeping them in a steel housing, which not only secures them against impacts but also increases their durability
• NdFeB magnets lose strength when exposed to high temperatures. After reaching 80°C, many of them experience permanent drop of strength (a factor is the shape and dimensions of the magnet). We offer magnets specially adapted to work at temperatures up to 230°C marked [AH], which are extremely resistant to heat
• Magnets exposed to a humid environment can rust. Therefore while using outdoors, we advise using waterproof magnets made of rubber, plastic or other material resistant to moisture
• Limited possibility of creating threads in the magnet and complicated shapes - recommended is cover - magnetic holder.
• Possible danger to health – tiny shards of magnets can be dangerous, when accidentally swallowed, which is particularly important in the aspect of protecting the youngest. Furthermore, tiny parts of these devices can be problematic in diagnostics medical in case of swallowing.
• Due to complex production process, their price is higher than average,

Maximum holding power of the magnet – what it depends on?

Breakaway force is the result of a measurement for ideal contact conditions, taking into account:

• on a block made of structural steel, optimally conducting the magnetic flux
• with a cross-section no less than 10 mm
• with a surface free of scratches
• under conditions of ideal adhesion (metal-to-metal)
• under axial force direction (90-degree angle)
• at room temperature

Impact of factors on magnetic holding capacity in practice

In real-world applications, the actual lifting capacity depends on many variables, listed from crucial:

• Air gap (between the magnet and the plate), because even a tiny clearance (e.g. 0.5 mm) results in a drastic drop in force by up to 50% (this also applies to varnish, rust or debris).
• Force direction – note that the magnet holds strongest perpendicularly. Under shear forces, the holding force drops drastically, often to levels of 20-30% of the nominal value.
• Element thickness – for full efficiency, the steel must be sufficiently thick. Paper-thin metal restricts the attraction force (the magnet "punches through" it).
• Plate material – low-carbon steel attracts best. Alloy steels lower magnetic permeability and lifting capacity.
• Surface condition – smooth surfaces guarantee perfect abutment, which improves force. Uneven metal reduce efficiency.
• Operating temperature – NdFeB sinters have a negative temperature coefficient. At higher temperatures they are weaker, and at low temperatures they can be stronger (up to a certain limit).

* Holding force was checked on a smooth steel plate of 20 mm thickness, when the force acted perpendicularly, whereas under parallel forces the lifting capacity is smaller. Moreover, even a minimal clearance {between} the magnet and the plate lowers the holding force.