MP 14x8/4x3 / N38 - ring magnet

Advantages as well as disadvantages of neodymium magnets NdFeB.

Apart from their consistent power, neodymium magnets have these key benefits:

• They virtually do not lose strength, because even after ten years, the decline in efficiency is only ~1% (according to literature),
• They remain magnetized despite exposure to magnetic noise,
• Thanks to the glossy finish and nickel coating, they have an elegant appearance,
• They have extremely strong magnetic induction on the surface of the magnet,
• 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 specific requirements, neodymium magnets can be created in different geometries, which expands their application range,
• Wide application in advanced technical fields – they serve a purpose in HDDs, rotating machines, clinical machines along with high-tech tools,
• Compactness – despite their small size, they deliver powerful magnetism, making them ideal for precision applications

Disadvantages of NdFeB magnets:

• They may fracture when subjected to a powerful impact. If the magnets are exposed to mechanical hits, it is suggested to place them in a protective case. The steel housing, in the form of a holder, protects the magnet from breakage and reinforces its overall robustness,
• Magnets lose magnetic efficiency when exposed to temperatures exceeding 80°C. In most cases, this leads to irreversible magnetic decay (influenced by the magnet’s profile). To address this, we provide [AH] models with superior thermal resistance, able to operate even at 230°C or more,
• Due to corrosion risk in humid conditions, it is common to use sealed magnets made of plastic for outdoor use,
• Limited ability to create internal holes 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 important in the health of young users. Additionally, tiny components from these magnets can disrupt scanning if inside the body,
• Due to expensive raw materials, their cost is relatively high,

Highest magnetic holding force – what contributes to it?

The given holding capacity of the magnet corresponds to the highest holding force, assessed in ideal conditions, that is:

• with the use of low-carbon steel plate serving as a magnetic yoke
• with a thickness of minimum 10 mm
• with a polished side
• with zero air gap
• with vertical force applied
• at room temperature

What influences lifting capacity in practice

The lifting capacity of a magnet is determined by in practice key elements, 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 the force acted perpendicularly, in contrast under attempts to slide the magnet the load capacity is reduced by as much as 75%. In addition, even a minimal clearance {between} the magnet and the plate lowers the lifting capacity.