MW 8x20 / N38 - cylindrical magnet

Strengths as well as weaknesses of neodymium magnets.

Besides their immense pulling force, neodymium magnets offer the following advantages:

• They have unchanged lifting capacity, and over more than 10 years their performance decreases symbolically – ~1% (in testing),
• They are extremely resistant to demagnetization induced by presence of other magnetic fields,
• Thanks to the glossy finish, the coating of nickel, gold, or silver gives an modern appearance,
• Magnets are distinguished by very high magnetic induction on the surface,
• 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...
• Due to the potential of flexible shaping and adaptation to custom needs, NdFeB magnets can be manufactured in a broad palette of forms and dimensions, which expands the range of possible applications,
• Universal use in advanced technology sectors – they are commonly used in mass storage devices, motor assemblies, advanced medical instruments, also technologically advanced constructions.
• Thanks to efficiency per cm³, small magnets offer high operating force, in miniature format,

Characteristics of disadvantages of neodymium magnets: weaknesses and usage proposals

• Susceptibility to cracking is one of their disadvantages. Upon intense impact they can break. We advise keeping them in a steel housing, which not only secures them against impacts but also raises their durability
• Neodymium magnets lose their power under the influence of heating. As soon as 80°C is exceeded, many of them start losing their power. Therefore, we recommend our special magnets marked [AH], which maintain durability even at temperatures up to 230°C
• Due to the susceptibility of magnets to corrosion in a humid environment, we advise using waterproof magnets made of rubber, plastic or other material stable to moisture, when using outdoors
• Limited possibility of making nuts in the magnet and complicated shapes - preferred is cover - mounting mechanism.
• Health risk related to microscopic parts of magnets pose a threat, in case of ingestion, which becomes key in the context of child safety. Additionally, small components of these products can be problematic in diagnostics medical after entering the body.
• With mass production the cost of neodymium magnets is economically unviable,

Magnetic strength at its maximum – what affects it?

Holding force of 8.85 kg is a result of laboratory testing executed under standard conditions:

• using a sheet made of mild steel, functioning as a ideal flux conductor
• with a cross-section no less than 10 mm
• with a plane perfectly flat
• under conditions of ideal adhesion (metal-to-metal)
• for force acting at a right angle (pull-off, not shear)
• in stable room temperature

Practical aspects of lifting capacity – factors

Holding efficiency is affected by specific conditions, including (from priority):

• Clearance – the presence of foreign body (paint, dirt, gap) interrupts the magnetic circuit, which lowers power rapidly (even by 50% at 0.5 mm).
• Force direction – catalog parameter refers to pulling vertically. When slipping, the magnet holds much less (typically approx. 20-30% of maximum force).
• Metal thickness – thin material does not allow full use of the magnet. Part of the magnetic field penetrates through instead of generating force.
• Material composition – different alloys attracts identically. High carbon content weaken the interaction with the magnet.
• Base smoothness – the more even the plate, the better the adhesion and higher the lifting capacity. Roughness creates an air distance.
• Heat – NdFeB sinters have a sensitivity to temperature. At higher temperatures they are weaker, and at low temperatures they can be stronger (up to a certain limit).

* Holding force was measured on a smooth steel plate of 20 mm thickness, when the force acted perpendicularly, in contrast under shearing force the holding force is lower. Additionally, even a minimal clearance {between} the magnet’s surface and the plate lowers the lifting capacity.