MP 41x15x10 / N38 - ring magnet

Advantages as well as disadvantages of neodymium magnets NdFeB.

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

• They do not lose their power around 10 years – the reduction of power is only ~1% (according to tests),
• They show strong resistance to demagnetization from outside magnetic sources,
• The use of a decorative nickel surface provides a refined finish,
• They possess significant magnetic force measurable at the magnet’s surface,
• With the right combination of compounds, they reach significant thermal stability, enabling operation at or above 230°C (depending on the structure),
• With the option for fine forming and precise design, these magnets can be produced in various shapes and sizes, greatly improving engineering flexibility,
• Important function in advanced technical fields – they find application in HDDs, electric motors, clinical machines or even technologically developed systems,
• 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, it is suggested to place them in a protective case. The steel housing, in the form of a holder, protects the magnet from cracks and additionally increases its overall strength,
• High temperatures may significantly reduce the holding force of neodymium magnets. Typically, above 80°C, they experience permanent weakening in performance (depending on shape). To prevent this, we offer heat-resistant magnets marked [AH], capable of working up to 230°C, which makes them perfect for high-temperature use,
• They rust in a wet environment – during outdoor use, we recommend using waterproof magnets, such as those made of polymer,
• Using a cover – such as a magnetic holder – is advised due to the restrictions in manufacturing threads directly in the magnet,
• Possible threat linked to microscopic shards may arise, especially if swallowed, which is notable in the protection of children. It should also be noted that miniature parts from these products may hinder health screening if inside the body,
• High unit cost – neodymium magnets are pricier than other types of magnets (e.g., ferrite), which can restrict large-scale applications

Best holding force of the magnet in ideal parameters – what affects it?

The given lifting capacity of the magnet represents the maximum lifting force, assessed in ideal conditions, namely:

• with mild steel, serving as a magnetic flux conductor
• having a thickness of no less than 10 millimeters
• with a refined outer layer
• in conditions of no clearance
• under perpendicular detachment force
• under standard ambient temperature

Determinants of practical lifting force of a magnet

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, since even a very small distance (e.g. 0.5 mm) can cause 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 using a polished steel plate of optimal thickness (min. 20 mm), under perpendicular pulling force, in contrast under parallel forces the load capacity is reduced by as much as 5 times. In addition, even a slight gap {between} the magnet’s surface and the plate decreases the lifting capacity.