MP 20x8/4x3 / N38 - ring magnet

Advantages as well as disadvantages of neodymium magnets NdFeB.

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

• Their magnetic field is maintained, and after approximately ten years, it drops only by ~1% (according to research),
• They show superior resistance to demagnetization from external magnetic fields,
• Because of the reflective layer of nickel, the component looks high-end,
• The outer field strength of the magnet shows remarkable magnetic properties,
• Thanks to their high temperature resistance, they can operate (depending on the shape) even at temperatures up to 230°C or more,
• The ability for accurate shaping or customization to custom needs – neodymium magnets can be manufactured in multiple variants of geometries, which extends the scope of their use cases,
• Key role in new technology industries – they serve a purpose in HDDs, electric drives, clinical machines and other advanced devices,
• Thanks to their efficiency per volume, small magnets offer high magnetic performance, in miniature format,

Disadvantages of magnetic elements:

• They are prone to breaking when subjected to a sudden 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 breakage and additionally strengthens its overall durability,
• They lose power at elevated temperatures. Most neodymium magnets experience permanent degradation 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 wise to use sealed magnets made of protective material for outdoor use,
• Using a cover – such as a magnetic holder – is advised due to the limitations in manufacturing complex structures directly in the magnet,
• Potential hazard linked to microscopic shards may arise, when consumed by mistake, which is significant in the protection of children. Additionally, small elements from these assemblies can complicate medical imaging after being swallowed,
• Due to a complex production process, their cost is considerably higher,

Detachment force of the magnet in optimal conditions – what it depends on?

The given pulling force of the magnet represents the maximum force, calculated in the best circumstances, that is:

• 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 polished side
• with zero air gap
• with vertical force applied
• in normal thermal conditions

Determinants of lifting force in real conditions

The lifting capacity of a magnet is influenced 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.

* Lifting capacity was determined using a smooth steel plate of suitable thickness (min. 20 mm), under perpendicular pulling force, in contrast under attempts to slide the magnet the load capacity is reduced by as much as 75%. Moreover, even a small distance {between} the magnet’s surface and the plate lowers the lifting capacity.