MW 15x4 / N38 - cylindrical magnet

Advantages and disadvantages of rare earth magnets.

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

• They have unchanged lifting capacity, and over around 10 years their performance decreases symbolically – ~1% (in testing),
• Neodymium magnets are distinguished by extremely resistant to magnetic field loss caused by external magnetic fields,
• By using a lustrous layer of gold, the element has an modern look,
• The surface of neodymium magnets generates a concentrated magnetic field – this is a key feature,
• Neodymium magnets are characterized by extremely high magnetic induction on the magnet surface and are able to act (depending on the form) even at a temperature of 230°C or more...
• Thanks to the ability of flexible molding and adaptation to individualized requirements, neodymium magnets can be produced in a wide range of geometric configurations, which expands the range of possible applications,
• Versatile presence in electronics industry – they serve a role in computer drives, motor assemblies, medical equipment, also modern systems.
• Compactness – despite small sizes they provide effective action, making them ideal for precision applications

Disadvantages of NdFeB magnets:

• To avoid cracks under impact, we recommend using special steel housings. Such a solution protects the magnet and simultaneously improves its durability.
• When exposed to high temperature, neodymium magnets experience a drop in power. 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
• When exposed to humidity, magnets start to rust. To use them in conditions outside, it is recommended to use protective magnets, such as those in rubber or plastics, which secure oxidation and corrosion.
• Limited ability of making nuts in the magnet and complex forms - preferred is casing - magnet mounting.
• Potential hazard to health – tiny shards of magnets are risky, in case of ingestion, which gains importance in the aspect of protecting the youngest. Furthermore, small elements of these devices are able to be problematic in diagnostics medical when they are in the body.
• Due to neodymium price, their price is higher than average,

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

Breakaway force was defined for ideal contact conditions, taking into account:

• using a sheet made of low-carbon steel, acting as a magnetic yoke
• possessing a massiveness of min. 10 mm to avoid saturation
• characterized by even structure
• with zero gap (without paint)
• for force applied at a right angle (pull-off, not shear)
• in temp. approx. 20°C

Lifting capacity in practice – influencing factors

Holding efficiency is influenced by working environment parameters, such as (from most important):

• Space between surfaces – even a fraction of a millimeter of distance (caused e.g. by veneer or dirt) drastically reduces the magnet efficiency, often by half at just 0.5 mm.
• Pull-off angle – note that the magnet holds strongest perpendicularly. Under shear forces, the holding force drops drastically, often to levels of 20-30% of the nominal value.
• Wall thickness – the thinner the sheet, the weaker the hold. Magnetic flux passes through the material instead of generating force.
• Metal type – not every steel attracts identically. High carbon content weaken the attraction effect.
• Surface finish – full contact is possible only on smooth steel. Rough texture reduce the real contact area, reducing force.
• Thermal factor – high temperature reduces magnetic field. Exceeding the limit temperature can permanently damage the magnet.

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