UMH 25x8x45 [M5] / N38 - magnetic holder with hook

Strengths as well as weaknesses of rare earth magnets.

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

• They retain magnetic properties for around 10 years – the drop is just ~1% (based on simulations),
• Magnets very well defend themselves against demagnetization caused by external fields,
• The use of an metallic coating of noble metals (nickel, gold, silver) causes the element to have aesthetics,
• The surface of neodymium magnets generates a maximum magnetic field – this is a key feature,
• Made from properly selected components, these magnets show impressive resistance to high heat, enabling them to function (depending on their form) at temperatures up to 230°C and above...
• Possibility of accurate machining and adapting to individual conditions,
• Key role in modern technologies – they serve a role in hard drives, drive modules, diagnostic systems, and modern systems.
• Thanks to concentrated force, small magnets offer high operating force, occupying minimum space,

Drawbacks and weaknesses of neodymium magnets and ways of using them

• Susceptibility to cracking is one of their disadvantages. Upon intense impact they can break. We recommend keeping them in a steel housing, which not only protects them against impacts but also raises their durability
• When exposed to high temperature, neodymium magnets suffer a drop in strength. Often, when the temperature exceeds 80°C, their strength decreases (depending on the size and shape of the magnet). For those who need magnets for extreme conditions, we offer [AH] versions withstanding up to 230°C
• They oxidize in a humid environment. For use outdoors we suggest using waterproof magnets e.g. in rubber, plastic
• We recommend cover - magnetic holder, due to difficulties in creating nuts inside the magnet and complex forms.
• Health risk related to microscopic parts of magnets can be dangerous, in case of ingestion, which is particularly important in the context of child safety. It is also worth noting that tiny parts of these devices can be problematic in diagnostics medical when they are in the body.
• High unit price – neodymium magnets cost more than other types of magnets (e.g. ferrite), which can limit application in large quantities

Maximum lifting force for a neodymium magnet – what affects it?

Breakaway force is the result of a measurement for optimal configuration, taking into account:

• with the contact of a yoke made of special test steel, ensuring full magnetic saturation
• whose thickness is min. 10 mm
• with an polished touching surface
• with zero gap (without impurities)
• under perpendicular force vector (90-degree angle)
• in temp. approx. 20°C

Practical aspects of lifting capacity – factors

In practice, the actual holding force is determined by a number of factors, presented from most significant:

• Clearance – the presence of foreign body (rust, tape, air) interrupts the magnetic circuit, which lowers power steeply (even by 50% at 0.5 mm).
• Loading method – declared lifting capacity refers to pulling vertically. When attempting to slide, the magnet exhibits much less (typically approx. 20-30% of nominal force).
• Steel thickness – too thin steel does not close the flux, causing part of the flux to be lost into the air.
• Plate material – low-carbon steel attracts best. Higher carbon content reduce magnetic permeability and lifting capacity.
• Plate texture – smooth surfaces guarantee perfect abutment, which increases force. Uneven metal reduce efficiency.
• Thermal environment – temperature increase results in weakening of induction. It is worth remembering the maximum operating temperature for a given model.

* 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 holding force is lower. Moreover, even a minimal clearance {between} the magnet and the plate reduces the lifting capacity.