MW 40x8 / N38 - cylindrical magnet

Advantages and disadvantages of neodymium magnets NdFeB.

In addition to their pulling strength, neodymium magnets provide the following advantages:

• They virtually do not lose strength, because even after 10 years, the performance loss is only ~1% (according to literature),
• Their ability to resist magnetic interference from external fields is impressive,
• Because of the reflective layer of gold, the component looks high-end,
• Magnetic induction on the surface of these magnets is impressively powerful,
• With the right combination of compounds, they reach increased thermal stability, enabling operation at or above 230°C (depending on the design),
• Thanks to the freedom in shaping and the capability to adapt to specific requirements, neodymium magnets can be created in various configurations, which broadens their application range,
• Key role in new technology industries – they find application in data storage devices, rotating machines, diagnostic apparatus and technologically developed systems,
• Thanks to their concentrated strength, small magnets offer high magnetic performance, in miniature format,

Disadvantages of NdFeB magnets:

• They may fracture when subjected to a strong impact. If the magnets are exposed to external force, we recommend in a metal holder. The steel housing, in the form of a holder, protects the magnet from damage and increases its overall robustness,
• High temperatures may significantly reduce the field efficiency of neodymium magnets. Typically, above 80°C, they experience permanent decline in performance (depending on size). To prevent this, we offer heat-resistant magnets marked [AH], capable of working up to 230°C, which makes them perfect for high-temperature use,
• Due to corrosion risk in humid conditions, it is recommended to use sealed magnets made of protective material for outdoor use,
• The use of a protective casing or external holder is recommended, since machining threads in neodymium magnets is not feasible,
• Health risk linked to microscopic shards may arise, in case of ingestion, which is notable in the family environments. Furthermore, minuscule fragments from these products may complicate medical imaging once in the system,
• Due to expensive raw materials, their cost is above average,

Best holding force of the magnet in ideal parameters – what it depends on?

The given holding capacity of the magnet represents the highest holding force, determined in ideal conditions, specifically:

• with the use of low-carbon steel plate serving as a magnetic yoke
• with a thickness of minimum 10 mm
• with a refined outer layer
• with zero air gap
• with vertical force applied
• under standard ambient temperature

Key elements affecting lifting force

Practical lifting force is determined by elements, listed from the most critical to the less significant:

• Air gap between the magnet and the plate, because 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 measured on the plate surface of 20 mm thickness, when the force acted perpendicularly, however under attempts to slide the magnet the lifting capacity is smaller. Moreover, even a minimal clearance {between} the magnet and the plate decreases the holding force.