MPL 25x25x10 / N38 - lamellar magnet

Advantages as well as disadvantages of rare earth magnets.

Besides their exceptional field intensity, neodymium magnets offer the following advantages:

• They retain full power for around ten years – the loss is just ~1% (in theory),
• Neodymium magnets remain exceptionally resistant to magnetic field loss caused by external field sources,
• A magnet with a shiny nickel surface is more attractive,
• They feature high magnetic induction at the operating surface, which improves attraction properties,
• Thanks to resistance to high temperature, they are capable of working (depending on the shape) even at temperatures up to 230°C and higher...
• Considering the option of free molding and customization to specialized solutions, neodymium magnets can be modeled in a wide range of forms and dimensions, which makes them more universal,
• Significant place in high-tech industry – they are commonly used in magnetic memories, electric drive systems, diagnostic systems, also technologically advanced constructions.
• Relatively small size with high pulling force – neodymium magnets offer impressive pulling force in small dimensions, which makes them useful in compact constructions

Cons of neodymium magnets: weaknesses and usage proposals

• Brittleness is one of their disadvantages. Upon intense impact they can fracture. We recommend keeping them in a strong case, which not only secures them against impacts but also raises their durability
• We warn that neodymium magnets can lose their strength at high temperatures. To prevent this, we recommend our specialized [AH] magnets, which work effectively even at 230°C.
• Magnets exposed to a humid environment can corrode. Therefore during using outdoors, we suggest using water-impermeable magnets made of rubber, plastic or other material protecting against moisture
• Limited ability of making threads in the magnet and complex forms - preferred is cover - magnet mounting.
• Health risk resulting from small fragments of magnets can be dangerous, if swallowed, which gains importance in the aspect of protecting the youngest. Additionally, small components of these magnets can disrupt the diagnostic process medical in case of swallowing.
• High unit price – neodymium magnets cost more than other types of magnets (e.g. ferrite), which increases costs of application in large quantities

Maximum lifting force for a neodymium magnet – what contributes to it?

Breakaway force is the result of a measurement for the most favorable conditions, assuming:

• on a plate made of structural steel, optimally conducting the magnetic field
• whose transverse dimension is min. 10 mm
• characterized by smoothness
• under conditions of gap-free contact (metal-to-metal)
• during detachment in a direction perpendicular to the mounting surface
• at ambient temperature room level

Impact of factors on magnetic holding capacity in practice

Real force is influenced by specific conditions, including (from priority):

• Distance – existence of any layer (paint, dirt, gap) interrupts the magnetic circuit, which lowers power rapidly (even by 50% at 0.5 mm).
• Load vector – highest force is obtained only during pulling at a 90° angle. The shear force of the magnet along the surface is standardly several times lower (approx. 1/5 of the lifting capacity).
• Steel thickness – insufficiently thick sheet does not close the flux, causing part of the power to be escaped to the other side.
• Steel type – mild steel gives the best results. Alloy steels reduce magnetic properties and holding force.
• Surface finish – full contact is possible only on polished steel. Rough texture reduce the real contact area, weakening the magnet.
• Operating temperature – neodymium magnets 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 tested on the plate surface of 20 mm thickness, when the force acted perpendicularly, in contrast under attempts to slide the magnet the lifting capacity is smaller. Additionally, even a minimal clearance {between} the magnet’s surface and the plate lowers the lifting capacity.