MP 20x8x6 / N38 - ring magnet

Strengths as well as weaknesses of rare earth magnets.

In addition to their long-term stability, neodymium magnets provide the following advantages:

• They virtually do not lose strength, because even after ten years the decline in efficiency is only ~1% (according to literature),
• Magnets very well resist against demagnetization caused by ambient magnetic noise,
• The use of an elegant finish of noble metals (nickel, gold, silver) causes the element to be more visually attractive,
• They feature high magnetic induction at the operating surface, which affects their effectiveness,
• Neodymium magnets are characterized by very high magnetic induction on the magnet surface and can function (depending on the form) even at a temperature of 230°C or more...
• Possibility of exact shaping and modifying to individual requirements,
• Wide application in modern industrial fields – they serve a role in hard drives, brushless drives, precision medical tools, also industrial machines.
• Compactness – despite small sizes they provide effective action, making them ideal for precision applications

Disadvantages of NdFeB magnets:

• At very strong impacts they can break, therefore we recommend placing them in steel cases. A metal housing provides additional protection against damage and increases the magnet's durability.
• When exposed to high temperature, neodymium magnets suffer a drop in power. Often, when the temperature exceeds 80°C, their power decreases (depending on the size and shape of the magnet). For those who need magnets for extreme conditions, we offer [AH] versions withstanding up to 230°C
• When exposed to humidity, magnets usually rust. To use them in conditions outside, it is recommended to use protective magnets, such as those in rubber or plastics, which prevent oxidation as well as corrosion.
• Due to limitations in creating threads and complicated forms in magnets, we propose using a housing - magnetic holder.
• Possible danger resulting from small fragments of magnets pose a threat, when accidentally swallowed, which gains importance in the aspect of protecting the youngest. It is also worth noting that small components of these magnets are able to complicate diagnosis medical after entering the body.
• Higher cost of purchase is one of the disadvantages compared to ceramic magnets, especially in budget applications

Maximum holding power of the magnet – what contributes to it?

Magnet power is the result of a measurement for ideal contact conditions, taking into account:

• on a block made of structural steel, perfectly concentrating the magnetic flux
• whose thickness equals approx. 10 mm
• with an ideally smooth contact surface
• under conditions of no distance (metal-to-metal)
• for force acting at a right angle (in the magnet axis)
• in stable room temperature

Lifting capacity in practice – influencing factors

Real force impacted by specific conditions, including (from most important):

• Gap between surfaces – even a fraction of a millimeter of distance (caused e.g. by veneer or unevenness) drastically reduces the magnet efficiency, often by half at just 0.5 mm.
• Force direction – note that the magnet has greatest strength perpendicularly. Under sliding down, the holding force drops significantly, often to levels of 20-30% of the nominal value.
• Substrate thickness – to utilize 100% power, the steel must be sufficiently thick. Thin sheet restricts the attraction force (the magnet "punches through" it).
• Steel grade – ideal substrate is pure iron steel. Stainless steels may have worse magnetic properties.
• Surface condition – smooth surfaces guarantee perfect abutment, which improves force. Uneven metal weaken the grip.
• Heat – NdFeB sinters have a sensitivity to temperature. At higher temperatures they are weaker, and at low temperatures they can be stronger (up to a certain limit).

* Lifting capacity was assessed using a steel plate with a smooth surface of optimal thickness (min. 20 mm), under vertically applied force, whereas under attempts to slide the magnet the lifting capacity is smaller. Moreover, even a slight gap {between} the magnet’s surface and the plate decreases the holding force.