AM Magnetyczny zbieracz / N38 - magnetic accessories

Advantages as well as disadvantages of neodymium magnets NdFeB.

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

• They have constant strength, and over nearly 10 years their attraction force decreases symbolically – ~1% (in testing),
• They are highly resistant to demagnetization caused by external magnetic fields,
• Thanks to the glossy finish and nickel coating, they have an elegant appearance,
• They possess strong magnetic force measurable at the magnet’s surface,
• Thanks to their enhanced temperature resistance, they can operate (depending on the shape) even at temperatures up to 230°C or more,
• With the option for tailored forming and precise design, these magnets can be produced in various shapes and sizes, greatly improving application potential,
• Wide application in new technology industries – they are used in hard drives, electromechanical systems, diagnostic apparatus or even other advanced devices,
• Compactness – despite their small size, they deliver powerful magnetism, making them ideal for precision applications

Disadvantages of rare earth magnets:

• They are prone to breaking when subjected to a sudden impact. If the magnets are exposed to mechanical hits, they should be placed in a metal holder. The steel housing, in the form of a holder, protects the magnet from cracks while also strengthens its overall resistance,
• High temperatures may significantly reduce the field efficiency of neodymium magnets. Typically, above 80°C, they experience permanent decline 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,
• Due to corrosion risk in humid conditions, it is recommended to use sealed magnets made of protective material for outdoor use,
• The use of a protective casing or external holder is recommended, since machining threads in neodymium magnets is restricted,
• Safety concern related to magnet particles may arise, when consumed by mistake, which is crucial in the protection of children. It should also be noted that small elements from these assemblies might interfere with diagnostics when ingested,
• Due to a complex production process, their cost is relatively high,

Maximum lifting force for a neodymium magnet – what contributes to it?

The given holding capacity of the magnet represents the highest holding force, calculated in the best circumstances, namely:

• with the use of low-carbon steel plate serving as a magnetic yoke
• with a thickness of minimum 10 mm
• with a smooth surface
• with zero air gap
• with vertical force applied
• at room temperature

Determinants of lifting force in real conditions

The lifting capacity of a magnet depends on 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 testing was carried out on a smooth plate of suitable thickness, under perpendicular forces, whereas under attempts to slide the magnet the holding force is lower. Moreover, even a minimal clearance {between} the magnet’s surface and the plate lowers the lifting capacity.