MW 12x2 / N38 - cylindrical magnet

Advantages as well as disadvantages of neodymium magnets NdFeB.

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

• They virtually do not lose power, because even after ten years, the performance loss is only ~1% (based on calculations),
• They are extremely resistant to demagnetization caused by external magnetic sources,
• Thanks to the glossy finish and nickel coating, they have an visually attractive appearance,
• Magnetic induction on the surface of these magnets is impressively powerful,
• These magnets tolerate high temperatures, often exceeding 230°C, when properly designed (in relation to profile),
• The ability for accurate shaping or adaptation to specific needs – neodymium magnets can be manufactured in a wide range of shapes and sizes, which enhances their versatility in applications,
• Wide application in advanced technical fields – they find application in HDDs, electric motors, medical equipment or even other advanced devices,
• Relatively small size with high magnetic force – neodymium magnets offer strong power in small dimensions, which makes them useful in small systems

Disadvantages of neodymium magnets:

• They can break when subjected to a strong impact. If the magnets are exposed to mechanical hits, it is suggested to place them in a protective enclosure. The steel housing, in the form of a holder, protects the magnet from breakage while also increases its overall durability,
• They lose field intensity at extreme temperatures. Most neodymium magnets experience permanent degradation in strength when heated above 80°C (depending on the form and height). However, we offer special variants with high temperature resistance that can operate up to 230°C or higher,
• Due to corrosion risk in humid conditions, it is wise to use sealed magnets made of protective material for outdoor use,
• Limited ability to create precision features in the magnet – the use of a external casing is recommended,
• Safety concern related to magnet particles may arise, in case of ingestion, which is important in the health of young users. Moreover, minuscule fragments from these devices can interfere with diagnostics when ingested,
• In cases of mass production, neodymium magnet cost may not be economically viable,

Magnetic strength at its maximum – what it depends on?

The given lifting capacity of the magnet means the maximum lifting force, calculated in the best circumstances, namely:

• using a steel plate with low carbon content, acting as a magnetic circuit closure
• with a thickness of minimum 10 mm
• with a polished side
• with zero air gap
• with vertical force applied
• under standard ambient temperature

Determinants of lifting force in real conditions

In practice, the holding capacity of a magnet is conditioned by the following aspects, in descending order of importance:

• Air gap between the magnet and the plate, since even a very small distance (e.g. 0.5 mm) causes a drop in lifting force of up to 50%.
• Direction of applied force, because the maximum lifting capacity is achieved under perpendicular application. The force required to slide the magnet along the plate is usually several times lower.
• Thickness of the plate, as a plate that is too thin causes part of the magnetic flux not to be used and to remain wasted in the air.
• Material of the plate, because higher carbon content lowers holding force, while higher iron content increases it. The best choice is steel with high magnetic permeability and high saturation induction.
• Surface of the plate, because the more smooth and polished it is, the better the contact and consequently the greater the magnetic saturation.
• Operating temperature, since all permanent magnets have a negative temperature coefficient. This means that at high temperatures they are weaker, while at sub-zero temperatures they become slightly stronger.

* Holding force was tested on the plate surface of 20 mm thickness, when the force acted perpendicularly, however under shearing force the lifting capacity is smaller. In addition, even a small distance {between} the magnet and the plate decreases the load capacity.