SMZR 32x125 / N52 - magnetic separator with handle

Strengths and weaknesses of rare earth magnets.

In addition to their magnetic efficiency, neodymium magnets provide the following advantages:

• They have constant strength, and over around ten years their attraction force decreases symbolically – ~1% (according to theory),
• Neodymium magnets prove to be exceptionally resistant to demagnetization caused by external interference,
• By applying a reflective layer of nickel, the element gains an elegant look,
• The surface of neodymium magnets generates a concentrated magnetic field – this is a key feature,
• Neodymium magnets are characterized by extremely high magnetic induction on the magnet surface and can work (depending on the shape) even at a temperature of 230°C or more...
• Thanks to the ability of precise forming and adaptation to specialized projects, neodymium magnets can be modeled in a variety of geometric configurations, which makes them more universal,
• Wide application in modern technologies – they are utilized in computer drives, brushless drives, medical equipment, and complex engineering applications.
• Relatively small size with high pulling force – neodymium magnets offer impressive pulling force in tiny dimensions, which enables their usage in compact constructions

Cons of neodymium magnets and proposals for their use:

• Susceptibility to cracking is one of their disadvantages. Upon strong impact they can fracture. We advise keeping them in a steel housing, which not only protects them against impacts but also raises their durability
• NdFeB magnets lose force when exposed to high temperatures. After reaching 80°C, many of them experience permanent weakening of strength (a factor is the shape as well as 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
• When exposed to humidity, magnets usually rust. For applications outside, it is recommended to use protective magnets, such as those in rubber or plastics, which secure oxidation and corrosion.
• Limited possibility of making threads in the magnet and complex shapes - recommended is cover - magnetic holder.
• Health risk to health – tiny shards of magnets pose a threat, when accidentally swallowed, which becomes key in the context of child health protection. Furthermore, tiny parts of these magnets can complicate diagnosis medical after entering the body.
• With large orders the cost of neodymium magnets is economically unviable,

Magnetic strength at its maximum – what contributes to it?

Information about lifting capacity is the result of a measurement for the most favorable conditions, assuming:

• using a base made of mild steel, serving as a ideal flux conductor
• with a cross-section of at least 10 mm
• characterized by lack of roughness
• without the slightest air gap between the magnet and steel
• under perpendicular force vector (90-degree angle)
• at ambient temperature approx. 20 degrees Celsius

Practical aspects of lifting capacity – factors

Holding efficiency is influenced by working environment parameters, such as (from priority):

• Gap (betwixt the magnet and the plate), as even a very small distance (e.g. 0.5 mm) can cause a drastic drop in lifting capacity by up to 50% (this also applies to varnish, rust or debris).
• Pull-off angle – note that the magnet has greatest strength perpendicularly. Under shear forces, the capacity drops significantly, often to levels of 20-30% of the nominal value.
• Substrate thickness – for full efficiency, the steel must be sufficiently thick. Thin sheet limits the attraction force (the magnet "punches through" it).
• Metal type – not every steel attracts identically. High carbon content worsen the attraction effect.
• Surface structure – the more even the surface, the better the adhesion and stronger the hold. Unevenness acts like micro-gaps.
• Heat – NdFeB sinters have a sensitivity to temperature. When it is hot they are weaker, and in frost they can be stronger (up to a certain limit).

* Lifting capacity was measured using a polished steel plate of suitable thickness (min. 20 mm), under perpendicular detachment force, however under attempts to slide the magnet the holding force is lower. In addition, even a small distance {between} the magnet’s surface and the plate reduces the holding force.