MP 20x8x6 / N38 - ring magnet

Advantages as well as disadvantages of neodymium magnets NdFeB.

Besides their stability, neodymium magnets are valued for these benefits:

• Their power is maintained, and after around 10 years, it drops only by ~1% (according to research),
• They show exceptional resistance to demagnetization from outside magnetic sources,
• The use of a decorative gold surface provides a refined finish,
• Magnetic induction on the surface of these magnets is notably high,
• These magnets tolerate high temperatures, often exceeding 230°C, when properly designed (in relation to build),
• The ability for custom shaping or adjustment to individual needs – neodymium magnets can be manufactured in many forms and dimensions, which extends the scope of their use cases,
• Important function in new technology industries – they are utilized in computer drives, electric motors, medical equipment and sophisticated instruments,
• Compactness – despite their small size, they provide high effectiveness, making them ideal for precision applications

Disadvantages of rare earth magnets:

• They are fragile when subjected to a sudden impact. If the magnets are exposed to physical collisions, they should be placed in a protective enclosure. The steel housing, in the form of a holder, protects the magnet from fracture while also reinforces its overall durability,
• Magnets lose field strength when exposed to temperatures exceeding 80°C. In most cases, this leads to irreversible power drop (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,
• They rust in a damp environment, especially when used outside, we recommend using moisture-resistant magnets, such as those made of rubber,
• Limited ability to create precision features in the magnet – the use of a mechanical support is recommended,
• Health risk from tiny pieces may arise, especially if swallowed, which is important in the context of child safety. It should also be noted that small elements from these assemblies can hinder health screening when ingested,
• High unit cost – neodymium magnets are pricier than other types of magnets (e.g., ferrite), which increases the cost of large-scale applications

Highest magnetic holding force – what contributes to it?

The given lifting capacity of the magnet corresponds to the maximum lifting force, measured in a perfect environment, namely:

• with mild steel, serving as a magnetic flux conductor
• having a thickness of no less than 10 millimeters
• with a smooth surface
• in conditions of no clearance
• under perpendicular detachment force
• in normal thermal conditions

What influences lifting capacity in practice

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) 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 checked on a smooth steel plate of 20 mm thickness, when a perpendicular force was applied, however under attempts to slide the magnet the lifting capacity is smaller. In addition, even a small distance {between} the magnet and the plate reduces the load capacity.