MP 12x8/4x3 / N38 - ring magnet

Advantages and disadvantages of neodymium magnets NdFeB.

Apart from their superior holding force, neodymium magnets have these key benefits:

• They virtually do not lose power, because even after ten years, the performance loss is only ~1% (based on calculations),
• They are highly resistant to demagnetization caused by external magnetic fields,
• The use of a polished silver surface provides a refined finish,
• The outer field strength of the magnet shows remarkable magnetic properties,
• Thanks to their exceptional temperature resistance, they can operate (depending on the form) even at temperatures up to 230°C or more,
• With the option for customized forming and precise design, these magnets can be produced in numerous shapes and sizes, greatly improving engineering flexibility,
• Important function in cutting-edge sectors – they serve a purpose in data storage devices, electromechanical systems, healthcare devices along with high-tech tools,
• Thanks to their power density, small magnets offer high magnetic performance, while occupying minimal space,

Disadvantages of NdFeB magnets:

• They may fracture when subjected to a strong impact. If the magnets are exposed to mechanical hits, it is suggested to place them in a metal holder. The steel housing, in the form of a holder, protects the magnet from fracture while also reinforces its overall strength,
• High temperatures may significantly reduce the field efficiency of neodymium magnets. Typically, above 80°C, they experience permanent weakening in performance (depending on shape). To prevent this, we offer heat-resistant magnets marked [AH], capable of working up to 230°C, which makes them perfect for high-temperature use,
• Magnets exposed to moisture can oxidize. Therefore, for outdoor applications, it's best to use waterproof types made of non-metallic composites,
• Limited ability to create threads in the magnet – the use of a external casing is recommended,
• Health risk due to small fragments may arise, in case of ingestion, which is crucial in the context of child safety. Additionally, miniature parts from these magnets have the potential to hinder health screening when ingested,
• In cases of mass production, neodymium magnet cost is a challenge,

Best holding force of the magnet in ideal parameters – what affects it?

The given strength of the magnet represents the optimal strength, calculated in the best circumstances, namely:

• using a steel plate with low carbon content, acting as a magnetic circuit closure
• with a thickness of minimum 10 mm
• with a refined outer layer
• with no separation
• under perpendicular detachment force
• under standard ambient temperature

Practical lifting capacity: influencing factors

Practical lifting force is dependent on elements, listed from the most critical to the less significant:

• Air gap between the magnet and the plate, since even a very small distance (e.g. 0.5 mm) causes a drop in lifting force of up to 50%.
• Direction of applied force, because the maximum lifting capacity is achieved under perpendicular application. The force required to slide the magnet along the plate is usually several times lower.
• Thickness of the plate, as a plate that is too thin causes part of the magnetic flux not to be used and to remain wasted in the air.
• Material of the plate, because higher carbon content lowers holding force, while higher iron content increases it. The best choice is steel with high magnetic permeability and high saturation induction.
• Surface of the plate, because the more smooth and polished it is, the better the contact and consequently the greater the magnetic saturation.
• Operating temperature, since all permanent magnets have a negative temperature coefficient. This means that at high temperatures they are weaker, while at sub-zero temperatures they become slightly stronger.

* Holding force was tested on the plate surface of 20 mm thickness, when a perpendicular force was applied, in contrast under attempts to slide the magnet the load capacity is reduced by as much as 5 times. Additionally, even a minimal clearance {between} the magnet’s surface and the plate reduces the load capacity.