MW 8x1.5 / N38 - cylindrical magnet

Strengths and weaknesses of rare earth magnets.

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

• They have stable power, and over around 10 years their attraction force decreases symbolically – ~1% (according to theory),
• They retain their magnetic properties even under strong external field,
• The use of an elegant finish of noble metals (nickel, gold, silver) causes the element to look better,
• The surface of neodymium magnets generates a concentrated magnetic field – this is one of their assets,
• Made from properly selected components, these magnets show impressive resistance to high heat, enabling them to function (depending on their shape) at temperatures up to 230°C and above...
• Due to the option of free molding and adaptation to specialized solutions, neodymium magnets can be modeled in a variety of forms and dimensions, which amplifies use scope,
• Huge importance in modern technologies – they are utilized in hard drives, brushless drives, medical equipment, as well as multitasking production systems.
• Compactness – despite small sizes they offer powerful magnetic field, making them ideal for precision applications

Disadvantages of NdFeB magnets:

• Brittleness is one of their disadvantages. Upon strong impact they can fracture. We advise keeping them in a special holder, which not only secures them against impacts but also raises their durability
• We warn that neodymium magnets can reduce their power 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 advise using water-impermeable magnets made of rubber, plastic or other material resistant to moisture
• Due to limitations in creating threads and complicated shapes in magnets, we recommend using casing - magnetic mechanism.
• Potential hazard resulting from small fragments of magnets pose a threat, if swallowed, which gains importance in the context of child safety. Additionally, small elements of these devices can be problematic in diagnostics medical after entering the body.
• High unit price – neodymium magnets are more expensive than other types of magnets (e.g. ferrite), which increases costs of application in large quantities

Optimal lifting capacity of a neodymium magnet – what contributes to it?

The lifting capacity listed is a measurement result conducted under standard conditions:

• on a block made of structural steel, perfectly concentrating the magnetic field
• with a thickness of at least 10 mm
• characterized by smoothness
• with zero gap (without impurities)
• during pulling in a direction perpendicular to the plane
• at temperature approx. 20 degrees Celsius

Determinants of lifting force in real conditions

In real-world applications, the actual lifting capacity depends on several key aspects, presented from crucial:

• Space between magnet and steel – every millimeter of separation (caused e.g. by veneer or dirt) drastically reduces the magnet efficiency, often by half at just 0.5 mm.
• Angle of force application – highest force is reached only during pulling at a 90° angle. The shear force of the magnet along the plate is standardly many times smaller (approx. 1/5 of the lifting capacity).
• Element thickness – for full efficiency, the steel must be sufficiently thick. Paper-thin metal limits the attraction force (the magnet "punches through" it).
• Material composition – different alloys reacts the same. Alloy additives weaken the interaction with the magnet.
• Surface finish – full contact is obtained only on polished steel. Any scratches and bumps reduce the real contact area, weakening the magnet.
• Heat – NdFeB sinters have a sensitivity to temperature. At higher temperatures they are weaker, and at low temperatures gain strength (up to a certain limit).

* Lifting capacity testing was conducted on a smooth plate of optimal thickness, under a perpendicular pulling force, whereas under parallel forces the holding force is lower. Moreover, even a minimal clearance {between} the magnet’s surface and the plate lowers the load capacity.