MW 20x5 / N38 - cylindrical magnet

Strengths as well as weaknesses of rare earth magnets.

Besides their magnetic performance, neodymium magnets are valued for these benefits:

• They have constant strength, and over around 10 years their performance decreases symbolically – ~1% (in testing),
• They have excellent resistance to magnetism drop as a result of external magnetic sources,
• A magnet with a smooth gold surface is more attractive,
• Magnetic induction on the working part of the magnet is strong,
• Neodymium magnets are characterized by extremely high magnetic induction on the magnet surface and can work (depending on the form) even at a temperature of 230°C or more...
• Possibility of custom machining and optimizing to precise needs,
• Versatile presence in future technologies – they are utilized in mass storage devices, electric drive systems, diagnostic systems, as well as technologically advanced constructions.
• Thanks to concentrated force, small magnets offer high operating force, with minimal size,

Disadvantages of NdFeB magnets:

• Brittleness is one of their disadvantages. Upon strong impact they can fracture. We advise keeping them in a steel housing, which not only protects them against impacts but also raises their durability
• We warn that neodymium magnets can lose their strength at high temperatures. To prevent this, we recommend our specialized [AH] magnets, which work effectively even at 230°C.
• Magnets exposed to a humid environment can rust. Therefore when using outdoors, we suggest using water-impermeable magnets made of rubber, plastic or other material protecting against moisture
• We recommend cover - magnetic mechanism, due to difficulties in producing nuts inside the magnet and complicated shapes.
• Health risk related to microscopic parts of magnets are risky, if swallowed, which gains importance in the context of child safety. Furthermore, tiny parts of these magnets can complicate diagnosis medical when they are in the body.
• High unit price – neodymium magnets cost more than other types of magnets (e.g. ferrite), which hinders application in large quantities

Magnetic strength at its maximum – what contributes to it?

The lifting capacity listed is a result of laboratory testing conducted under the following configuration:

• using a plate made of mild steel, acting as a ideal flux conductor
• possessing a thickness of at least 10 mm to avoid saturation
• characterized by smoothness
• without the slightest insulating layer between the magnet and steel
• during pulling in a direction perpendicular to the plane
• in neutral thermal conditions

Practical aspects of lifting capacity – factors

During everyday use, the real power results from many variables, presented from crucial:

• Air gap (between the magnet and the metal), as even a microscopic clearance (e.g. 0.5 mm) leads to a reduction in lifting capacity by up to 50% (this also applies to paint, rust or debris).
• Pull-off angle – note that the magnet has greatest strength perpendicularly. Under sliding down, the holding force drops drastically, often to levels of 20-30% of the nominal value.
• Substrate thickness – to utilize 100% power, the steel must be sufficiently thick. Thin sheet restricts the attraction force (the magnet "punches through" it).
• Plate material – mild steel attracts best. Alloy admixtures decrease magnetic permeability and holding force.
• Surface structure – the smoother and more polished the plate, the larger the contact zone and higher the lifting capacity. Unevenness acts like micro-gaps.
• Thermal environment – temperature increase causes a temporary drop of induction. It is worth remembering the thermal limit for a given model.

* Lifting capacity testing was performed on a smooth plate of optimal thickness, under perpendicular forces, however under shearing force the lifting capacity is smaller. Moreover, even a minimal clearance {between} the magnet and the plate reduces the holding force.