MW 15x2 / N38 - cylindrical magnet

Advantages as well as disadvantages of neodymium magnets NdFeB.

Apart from their notable holding force, neodymium magnets have these key benefits:

• Their strength remains stable, and after around ten years, it drops only by ~1% (according to research),
• They show strong resistance to demagnetization from outside magnetic sources,
• The use of a polished gold surface provides a smooth finish,
• They exhibit extremely high levels of magnetic induction near the outer area of the magnet,
• Thanks to their enhanced temperature resistance, they can operate (depending on the form) even at temperatures up to 230°C or more,
• With the option for customized forming and targeted design, these magnets can be produced in numerous shapes and sizes, greatly improving application potential,
• Significant impact in advanced technical fields – they serve a purpose in HDDs, rotating machines, clinical machines or even other advanced devices,
• Relatively small size with high magnetic force – neodymium magnets offer impressive pulling strength in tiny dimensions, which allows for use in small systems

Disadvantages of magnetic elements:

• They may fracture when subjected to a sudden impact. If the magnets are exposed to shocks, they should be placed in a metal holder. The steel housing, in the form of a holder, protects the magnet from damage and additionally increases its overall strength,
• High temperatures may significantly reduce the holding force of neodymium magnets. Typically, above 80°C, they experience permanent loss 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,
• Magnets exposed to humidity can corrode. Therefore, for outdoor applications, we suggest waterproof types made of non-metallic composites,
• The use of a protective casing or external holder is recommended, since machining internal cuts in neodymium magnets is not feasible,
• Safety concern due to small fragments may arise, in case of ingestion, which is significant in the context of child safety. It should also be noted that tiny components from these assemblies might disrupt scanning after being swallowed,
• High unit cost – neodymium magnets are pricier than other types of magnets (e.g., ferrite), which can restrict large-scale applications

Highest magnetic holding force – what affects it?

The given strength of the magnet means the optimal strength, determined in the best circumstances, specifically:

• with the use of low-carbon steel plate serving as a magnetic yoke
• with a thickness of minimum 10 mm
• with a polished side
• with no separation
• under perpendicular detachment force
• under standard ambient temperature

Impact of factors on magnetic holding capacity in practice

In practice, the holding capacity of a magnet is affected by the following aspects, arranged from the most important to the least relevant:

• 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 measured on the plate surface of 20 mm thickness, when a perpendicular force was applied, whereas under attempts to slide the magnet the holding force is lower. In addition, even a minimal clearance {between} the magnet’s surface and the plate lowers the holding force.