MP 8x6/3.5x3 / N38 - ring magnet

Advantages as well as disadvantages of neodymium magnets NdFeB.

Besides their magnetic performance, neodymium magnets are valued for these benefits:

• Their magnetic field remains stable, and after around ten years, it drops only by ~1% (theoretically),
• They are extremely resistant to demagnetization caused by external field interference,
• In other words, due to the glossy nickel coating, the magnet obtains an professional appearance,
• The outer field strength of the magnet shows elevated magnetic properties,
• Thanks to their enhanced temperature resistance, they can operate (depending on the shape) even at temperatures up to 230°C or more,
• Thanks to the flexibility in shaping and the capability to adapt to unique requirements, neodymium magnets can be created in diverse shapes and sizes, which expands their usage potential,
• Significant impact in advanced technical fields – they are used in data storage devices, rotating machines, clinical machines as well as high-tech tools,
• Relatively small size with high magnetic force – neodymium magnets offer strong power in compact dimensions, which makes them useful in miniature devices

Disadvantages of NdFeB magnets:

• They can break when subjected to a sudden impact. If the magnets are exposed to mechanical hits, it is suggested to place them in a protective enclosure. The steel housing, in the form of a holder, protects the magnet from breakage and reinforces its overall durability,
• They lose strength at high temperatures. Most neodymium magnets experience permanent reduction 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,
• Using a cover – such as a magnetic holder – is advised due to the difficulty in manufacturing threads directly in the magnet,
• Safety concern due to small fragments may arise, in case of ingestion, which is significant in the health of young users. Additionally, small elements from these magnets can complicate medical imaging when ingested,
• Due to expensive raw materials, their cost is considerably higher,

Magnetic strength at its maximum – what contributes to it?

The given pulling force of the magnet corresponds to the maximum force, assessed in a perfect environment, specifically:

• using a steel plate with low carbon content, acting as a magnetic circuit closure
• having a thickness of no less than 10 millimeters
• with a smooth surface
• with no separation
• under perpendicular detachment force
• under standard ambient temperature

Magnet lifting force in use – key factors

In practice, the holding capacity of a magnet is affected by these factors, arranged from the most important to the least relevant:

• Air gap between the magnet and the plate, because even a very small distance (e.g. 0.5 mm) can cause 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 the force acted perpendicularly, in contrast under parallel forces the load capacity is reduced by as much as fivefold. Additionally, even a slight gap {between} the magnet’s surface and the plate decreases the lifting capacity.