MW 20x5 / N38 - cylindrical magnet

Strengths as well as weaknesses of NdFeB magnets.

Apart from their consistent magnetism, neodymium magnets have these key benefits:

• They have constant strength, and over nearly 10 years their attraction force decreases symbolically – ~1% (in testing),
• Magnets perfectly protect themselves against demagnetization caused by foreign field sources,
• A magnet with a smooth silver surface is more attractive,
• They are known for high magnetic induction at the operating surface, making them more effective,
• Made from properly selected components, these magnets show impressive resistance to high heat, enabling them to function (depending on their shape) at temperatures up to 230°C and above...
• Thanks to the ability of precise shaping and adaptation to specialized solutions, NdFeB magnets can be modeled in a variety of forms and dimensions, which makes them more universal,
• Huge importance in advanced technology sectors – they serve a role in data components, motor assemblies, advanced medical instruments, and other advanced devices.
• Compactness – despite small sizes they generate large force, making them ideal for precision applications

Problematic aspects of neodymium magnets: weaknesses and usage proposals

• Brittleness is one of their disadvantages. Upon strong impact they can fracture. We recommend keeping them in a steel housing, which not only secures them against impacts but also raises their durability
• We warn that neodymium magnets can reduce their strength at high temperatures. To prevent this, we advise our specialized [AH] magnets, which work effectively even at 230°C.
• When exposed to humidity, magnets start to rust. For applications outside, it is recommended to use protective magnets, such as those in rubber or plastics, which prevent oxidation as well as corrosion.
• We recommend a housing - magnetic mount, due to difficulties in producing nuts inside the magnet and complex forms.
• Possible danger to health – tiny shards of magnets pose a threat, in case of ingestion, which is particularly important in the context of child health protection. Furthermore, tiny parts of these magnets can complicate diagnosis medical when they are in the body.
• With large orders the cost of neodymium magnets is a challenge,

Maximum holding power of the magnet – what affects it?

Holding force of 5.53 kg is a measurement result performed under standard conditions:

• with the contact of a yoke made of special test steel, guaranteeing full magnetic saturation
• whose transverse dimension is min. 10 mm
• with an ideally smooth touching surface
• without any clearance between the magnet and steel
• for force acting at a right angle (in the magnet axis)
• in stable room temperature

Practical aspects of lifting capacity – factors

It is worth knowing that the magnet holding may be lower depending on the following factors, in order of importance:

• Clearance – the presence of foreign body (rust, tape, gap) acts as an insulator, which reduces power steeply (even by 50% at 0.5 mm).
• Direction of force – highest force is available only during perpendicular pulling. The shear force of the magnet along the plate is usually several times smaller (approx. 1/5 of the lifting capacity).
• Metal thickness – the thinner the sheet, the weaker the hold. Magnetic flux passes through the material instead of converting into lifting capacity.
• Plate material – low-carbon steel gives the best results. Alloy admixtures lower magnetic properties and holding force.
• Surface quality – the smoother and more polished the plate, the larger the contact zone and stronger the hold. Roughness creates an air distance.
• Thermal factor – hot environment weakens pulling force. Exceeding the limit temperature can permanently demagnetize the magnet.

* Holding force was measured on the plate surface of 20 mm thickness, when a perpendicular force was applied, in contrast under attempts to slide the magnet the holding force is lower. Moreover, even a slight gap {between} the magnet’s surface and the plate decreases the load capacity.