MP 62x42x25 / N38 - ring magnet

Advantages as well as disadvantages of rare earth magnets.

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

• They have unchanged lifting capacity, and over around ten years their performance decreases symbolically – ~1% (according to theory),
• Magnets effectively protect themselves against loss of magnetization caused by foreign field sources,
• In other words, due to the aesthetic layer of nickel, the element becomes visually attractive,
• The surface of neodymium magnets generates a strong magnetic field – this is one of their assets,
• They are suitable for high-temperature applications, operating effectively at 230°C+ due to advanced heat resistance and form-specific properties,
• Thanks to freedom in shaping and the capacity to modify to complex applications,
• Significant place in high-tech industry – they are commonly used in hard drives, motor assemblies, advanced medical instruments, also multitasking production systems.
• Thanks to efficiency per cm³, small magnets offer high operating force, in miniature format,

Characteristics of disadvantages 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 strong case, which not only secures them against impacts but also raises their durability
• NdFeB magnets lose force when exposed to high temperatures. After reaching 80°C, many of them experience permanent weakening of strength (a factor is the shape as well as dimensions of the magnet). We offer magnets specially adapted to work at temperatures up to 230°C marked [AH], which are extremely resistant to heat
• Due to the susceptibility of magnets to corrosion in a humid environment, we advise using waterproof magnets made of rubber, plastic or other material resistant to moisture, in case of application outdoors
• We recommend a housing - magnetic holder, due to difficulties in realizing threads inside the magnet and complex forms.
• Health risk to health – tiny shards of magnets pose a threat, when accidentally swallowed, which is particularly important in the context of child safety. It is also worth noting that small components of these devices are able to complicate diagnosis medical when they are in the body.
• High unit price – neodymium magnets are more expensive than other types of magnets (e.g. ferrite), which hinders application in large quantities

Breakaway strength of the magnet in ideal conditions – what it depends on?

The declared magnet strength refers to the peak performance, recorded under laboratory conditions, specifically:

• on a plate made of mild steel, effectively closing the magnetic field
• possessing a massiveness of minimum 10 mm to ensure full flux closure
• with a surface perfectly flat
• with zero gap (no paint)
• during detachment in a direction vertical to the plane
• at ambient temperature room level

Determinants of practical lifting force of a magnet

In practice, the actual lifting capacity results from a number of factors, presented from the most important:

• Space between magnet and steel – even a fraction of a millimeter of distance (caused e.g. by varnish or dirt) significantly weakens the magnet efficiency, often by half at just 0.5 mm.
• Force direction – remember that the magnet holds strongest perpendicularly. Under shear forces, the holding force drops drastically, often to levels of 20-30% of the nominal value.
• Plate thickness – insufficiently thick plate causes magnetic saturation, causing part of the flux to be lost into the air.
• Steel grade – the best choice is pure iron steel. Hardened steels may attract less.
• Plate texture – smooth surfaces guarantee perfect abutment, which improves force. Uneven metal reduce efficiency.
• Thermal factor – high temperature weakens pulling force. Exceeding the limit temperature can permanently demagnetize the magnet.

* Holding force was checked on the plate surface of 20 mm thickness, when a perpendicular force was applied, whereas under shearing force the lifting capacity is smaller. In addition, even a small distance {between} the magnet and the plate lowers the load capacity.