MPL 40x10x4 / N38 - lamellar magnet

Pros and cons of rare earth magnets.

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

• They do not lose strength, even over nearly ten years – the decrease in power is only ~1% (theoretically),
• Neodymium magnets remain highly resistant to magnetic field loss caused by external magnetic fields,
• A magnet with a smooth silver surface is more attractive,
• They show high magnetic induction at the operating surface, making them more effective,
• Thanks to resistance to high temperature, they are capable of working (depending on the form) even at temperatures up to 230°C and higher...
• Possibility of exact creating and modifying to specific needs,
• Significant place in modern industrial fields – they are utilized in magnetic memories, motor assemblies, medical equipment, as well as technologically advanced constructions.
• Relatively small size with high pulling force – neodymium magnets offer strong magnetic field in small dimensions, which enables their usage in compact constructions

Disadvantages of neodymium magnets:

• At very strong impacts they can break, therefore we recommend placing them in steel cases. A metal housing provides additional protection against damage, as well as increases the magnet's durability.
• Neodymium magnets lose their strength under the influence of heating. As soon as 80°C is exceeded, many of them start losing their force. Therefore, we recommend our special magnets marked [AH], which maintain durability even at temperatures up to 230°C
• They rust in a humid environment. For use outdoors we advise using waterproof magnets e.g. in rubber, plastic
• Limited possibility of producing threads in the magnet and complex forms - recommended is casing - magnetic holder.
• Possible danger to health – tiny shards of magnets pose a threat, when accidentally swallowed, which gains importance in the context of child health protection. Additionally, small elements of these magnets are able to be problematic in diagnostics medical when they are in the body.
• High unit price – neodymium magnets have a higher price 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?

The declared magnet strength represents the peak performance, measured under ideal test conditions, specifically:

• on a plate made of structural steel, effectively closing the magnetic flux
• whose thickness equals approx. 10 mm
• characterized by even structure
• under conditions of ideal adhesion (metal-to-metal)
• during pulling in a direction vertical to the plane
• at standard ambient temperature

Practical lifting capacity: influencing factors

Holding efficiency is affected by working environment parameters, including (from most important):

• Distance (betwixt the magnet and the plate), as even a tiny clearance (e.g. 0.5 mm) results in a decrease in lifting capacity by up to 50% (this also applies to paint, corrosion or dirt).
• Force direction – declared lifting capacity refers to pulling vertically. When applying parallel force, the magnet exhibits significantly lower power (often approx. 20-30% of nominal force).
• Substrate thickness – to utilize 100% power, the steel must be sufficiently thick. Thin sheet limits the attraction force (the magnet "punches through" it).
• Material composition – not every steel reacts the same. Alloy additives worsen the attraction effect.
• Surface finish – ideal contact is possible only on polished steel. Any scratches and bumps reduce the real contact area, reducing force.
• Operating temperature – NdFeB sinters have a negative temperature coefficient. When it is hot they lose power, and in frost gain strength (up to a certain limit).

* Holding force was measured on a smooth steel plate of 20 mm thickness, when a perpendicular force was applied, whereas under attempts to slide the magnet the holding force is lower. Additionally, even a slight gap {between} the magnet’s surface and the plate decreases the holding force.