MP 10x6x4 / N38 - ring magnet

Advantages as well as disadvantages of neodymium magnets NdFeB.

In addition to their exceptional field intensity, neodymium magnets offer the following advantages:

• They virtually do not lose strength, because even after ten years, the performance loss is only ~1% (based on calculations),
• Their ability to resist magnetic interference from external fields is among the best,
• By applying a reflective layer of nickel, the element gains a modern look,
• They have extremely strong magnetic induction on the surface of the magnet,
• Thanks to their exceptional temperature resistance, they can operate (depending on the shape) even at temperatures up to 230°C or more,
• With the option for customized forming and targeted design, these magnets can be produced in various shapes and sizes, greatly improving engineering flexibility,
• Significant impact in new technology industries – they are used in computer drives, rotating machines, medical equipment along with technologically developed systems,
• Thanks to their power density, small magnets offer high magnetic performance, in miniature format,

Disadvantages of rare earth magnets:

• They can break when subjected to a strong impact. If the magnets are exposed to external force, it is advisable to use in a protective case. The steel housing, in the form of a holder, protects the magnet from damage and additionally enhances its overall strength,
• Magnets lose field strength when exposed to temperatures exceeding 80°C. In most cases, this leads to irreversible performance loss (influenced by the magnet’s form). To address this, we provide [AH] models with superior thermal resistance, able to operate even at 230°C or more,
• Magnets exposed to moisture can rust. Therefore, for outdoor applications, we recommend waterproof types made of coated materials,
• The use of a protective casing or external holder is recommended, since machining threads in neodymium magnets is risky,
• Potential hazard due to small fragments may arise, in case of ingestion, which is important in the family environments. Additionally, minuscule fragments from these assemblies can complicate medical imaging once in the system,
• In cases of mass production, neodymium magnet cost may be a barrier,

Highest magnetic holding force – what contributes to it?

The given strength of the magnet represents the optimal strength, measured in ideal conditions, specifically:

• using a steel plate with low carbon content, serving as a magnetic circuit closure
• of a thickness of at least 10 mm
• with a polished side
• with zero air gap
• in a perpendicular direction of force
• in normal thermal conditions

Practical aspects of lifting capacity – factors

In practice, the holding capacity of a magnet is affected by these factors, from crucial to less important:

• Air gap between the magnet and the plate, because 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 assessed with the use of a polished steel plate of optimal thickness (min. 20 mm), under perpendicular detachment force, in contrast under shearing force the holding force is lower. In addition, even a slight gap {between} the magnet and the plate reduces the load capacity.