MP 5x2.7/1.2x5 C / N38 - ring magnet

Advantages as well as disadvantages of neodymium magnets NdFeB.

In addition to their tremendous strength, neodymium magnets offer the following advantages:

• They retain their attractive force for around ten years – the drop is just ~1% (according to analyses),
• They remain magnetized despite exposure to strong external fields,
• By applying a bright layer of silver, the element gains a clean look,
• They exhibit elevated levels of magnetic induction near the outer area of the magnet,
• These magnets tolerate extreme temperatures, often exceeding 230°C, when properly designed (in relation to build),
• Thanks to the flexibility in shaping and the capability to adapt to individual requirements, neodymium magnets can be created in diverse shapes and sizes, which increases their application range,
• Significant impact in new technology industries – they serve a purpose in HDDs, electric drives, clinical machines along with sophisticated instruments,
• Thanks to their efficiency per volume, small magnets offer high magnetic performance, while occupying minimal space,

Disadvantages of NdFeB magnets:

• They are fragile when subjected to a heavy impact. If the magnets are exposed to physical collisions, they should be placed in a protective enclosure. The steel housing, in the form of a holder, protects the magnet from cracks , and at the same time increases its overall strength,
• They lose magnetic force at increased temperatures. Most neodymium magnets experience permanent decline in strength when heated above 80°C (depending on the geometry and height). However, we offer special variants with high temperature resistance that can operate up to 230°C or higher,
• Due to corrosion risk in humid conditions, it is common to use sealed magnets made of plastic for outdoor use,
• Limited ability to create complex details in the magnet – the use of a mechanical support is recommended,
• Safety concern from tiny pieces may arise, if ingested accidentally, which is crucial in the family environments. Furthermore, small elements from these assemblies might complicate medical imaging when ingested,
• Higher purchase price is one of the drawbacks compared to ceramic magnets, especially in budget-sensitive applications

Maximum lifting force for a neodymium magnet – what contributes to it?

The given strength of the magnet represents the optimal strength, measured in ideal conditions, namely:

• with mild steel, used as a magnetic flux conductor
• having a thickness of no less than 10 millimeters
• with a refined outer layer
• with no separation
• under perpendicular detachment force
• in normal thermal conditions

Lifting capacity in real conditions – factors

The lifting capacity of a magnet depends on in practice the following factors, from primary to secondary:

• Air gap between the magnet and the plate, as 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 measured on a smooth steel plate of 20 mm thickness, when a perpendicular force was applied, however under attempts to slide the magnet the load capacity is reduced by as much as 75%. Additionally, even a minimal clearance {between} the magnet’s surface and the plate decreases the load capacity.