MW 20x5 / N38 - cylindrical magnet

Advantages as well as disadvantages of neodymium magnets NdFeB.

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

• They retain their magnetic properties for around ten years – the drop is just ~1% (based on simulations),
• They remain magnetized despite exposure to strong external fields,
• Thanks to the polished finish and nickel coating, they have an aesthetic appearance,
• The outer field strength of the magnet shows remarkable magnetic properties,
• Neodymium magnets are known for exceptionally strong magnetic induction and the ability to work at temperatures up to 230°C or higher (depending on the shape),
• The ability for precise shaping or adjustment to specific needs – neodymium magnets can be manufactured in a wide range of shapes and sizes, which enhances their versatility in applications,
• Key role in advanced technical fields – they are used in HDDs, electromechanical systems, medical equipment along with other advanced devices,
• Thanks to their power density, small magnets offer high magnetic performance, with minimal size,

Disadvantages of rare earth magnets:

• They can break when subjected to a heavy impact. If the magnets are exposed to external force, we recommend in a steel housing. The steel housing, in the form of a holder, protects the magnet from fracture and additionally increases its overall resistance,
• They lose field intensity at increased 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,
• Magnets exposed to damp air can rust. Therefore, for outdoor applications, it's best to use waterproof types made of non-metallic composites,
• Using a cover – such as a magnetic holder – is advised due to the challenges in manufacturing fine shapes directly in the magnet,
• Safety concern related to magnet particles may arise, if ingested accidentally, which is significant in the context of child safety. Moreover, miniature parts from these products have the potential to interfere with diagnostics if inside the body,
• In cases of mass production, neodymium magnet cost may not be economically viable,

Maximum magnetic pulling force – what affects it?

The given holding capacity of the magnet means the highest holding force, assessed in ideal conditions, namely:

• with mild steel, used as a magnetic flux conductor
• of a thickness of at least 10 mm
• with a smooth surface
• with zero air gap
• with vertical force applied
• at room temperature

Impact of factors on magnetic holding capacity in practice

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, 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.

* Lifting capacity was measured using a steel plate with a smooth surface of optimal thickness (min. 20 mm), under vertically applied force, in contrast under attempts to slide the magnet the lifting capacity is smaller. In addition, even a minimal clearance {between} the magnet and the plate decreases the lifting capacity.