MP 40x22x10 / N38 - ring magnet

Advantages as well as disadvantages of neodymium magnets NdFeB.

Apart from their superior power, neodymium magnets have these key benefits:

• They have constant strength, and over around ten years their attraction force decreases symbolically – ~1% (in testing),
• They show exceptional resistance to demagnetization from external field exposure,
• Thanks to the glossy finish and gold coating, they have an aesthetic appearance,
• They possess significant magnetic force measurable at the magnet’s surface,
• They are suitable for high-temperature applications, operating effectively at 230°C+ due to advanced heat resistance and form-specific properties,
• The ability for custom shaping and adjustment to custom needs – neodymium magnets can be manufactured in many forms and dimensions, which extends the scope of their use cases,
• Wide application in new technology industries – they are used in computer drives, electromechanical systems, diagnostic apparatus along with technologically developed systems,
• Compactness – despite their small size, they generate strong force, making them ideal for precision applications

Disadvantages of NdFeB magnets:

• They are prone to breaking when subjected to a sudden impact. If the magnets are exposed to external force, we recommend in a protective enclosure. The steel housing, in the form of a holder, protects the magnet from fracture and reinforces its overall durability,
• High temperatures may significantly reduce the holding force of neodymium magnets. Typically, above 80°C, they experience permanent deterioration in performance (depending on height). 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 damp environment – during outdoor use, we recommend using moisture-resistant magnets, such as those made of plastic,
• The use of a protective casing or external holder is recommended, since machining threads in neodymium magnets is risky,
• Health risk due to small fragments may arise, when consumed by mistake, which is crucial in the context of child safety. It should also be noted that minuscule fragments from these products may disrupt scanning once in the system,
• High unit cost – neodymium magnets are more expensive than other types of magnets (e.g., ferrite), which may limit large-scale applications

Maximum holding power of the magnet – what affects it?

The given pulling force of the magnet corresponds to the maximum force, measured under optimal conditions, that is:

• with mild steel, serving as a magnetic flux conductor
• of a thickness of at least 10 mm
• with a refined outer layer
• in conditions of no clearance
• under perpendicular detachment force
• at room temperature

Magnet lifting force in use – key factors

The lifting capacity of a magnet is determined 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 the plate surface of 20 mm thickness, when the force acted perpendicularly, in contrast under attempts to slide the magnet the load capacity is reduced by as much as 75%. Moreover, even a slight gap {between} the magnet and the plate decreases the holding force.