UMT 20x25 black / N38 - board holder

Advantages and disadvantages of neodymium magnets NdFeB.

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

• They retain their attractive force for almost 10 years – the drop is just ~1% (in theory),
• They protect against demagnetization induced by ambient electromagnetic environments effectively,
• Thanks to the polished finish and silver coating, they have an aesthetic appearance,
• They possess intense magnetic force measurable at the magnet’s surface,
• Neodymium magnets are known for very high magnetic induction and the ability to work at temperatures up to 230°C or higher (depending on the shape),
• The ability for custom shaping and customization to custom needs – neodymium magnets can be manufactured in a wide range of shapes and sizes, which enhances their versatility in applications,
• Key role in new technology industries – they find application in HDDs, electric motors, healthcare devices and high-tech tools,
• Compactness – despite their small size, they provide high effectiveness, making them ideal for precision applications

Disadvantages of magnetic elements:

• They can break when subjected to a strong impact. If the magnets are exposed to physical collisions, it is suggested to place them in a steel housing. The steel housing, in the form of a holder, protects the magnet from cracks and additionally strengthens its overall robustness,
• They lose power at elevated temperatures. Most neodymium magnets experience permanent decline in strength when heated above 80°C (depending on the form 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 advisable to use sealed magnets made of plastic for outdoor use,
• Using a cover – such as a magnetic holder – is advised due to the challenges in manufacturing holes directly in the magnet,
• Safety concern linked to microscopic shards may arise, if ingested accidentally, which is important in the family environments. Moreover, tiny components from these assemblies may interfere with diagnostics when ingested,
• Higher purchase price is an important factor to consider compared to ceramic magnets, especially in budget-sensitive applications

Maximum magnetic pulling force – what affects it?

The given strength of the magnet corresponds to the optimal strength, calculated under optimal conditions, that is:

• with the use of low-carbon steel plate acting as a magnetic yoke
• having a thickness of no less than 10 millimeters
• with a smooth surface
• with zero air gap
• under perpendicular detachment force
• under standard ambient temperature

Determinants of practical lifting force of a magnet

The lifting capacity of a magnet is influenced by in practice the following factors, ordered from most important to least significant:

• Air gap between the magnet and the plate, since 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.

* Lifting capacity was assessed with the use of a polished steel plate of suitable thickness (min. 20 mm), under perpendicular pulling force, however under attempts to slide the magnet the load capacity is reduced by as much as fivefold. Moreover, even a minimal clearance {between} the magnet’s surface and the plate lowers the load capacity.