MW 5x15 / N38 - cylindrical magnet

Advantages as well as disadvantages of neodymium magnets NdFeB.

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

• They do not lose their power nearly 10 years – the reduction of strength is only ~1% (according to tests),
• They protect against demagnetization induced by surrounding electromagnetic environments remarkably well,
• By applying a reflective layer of silver, the element gains a clean look,
• They possess intense magnetic force measurable at the magnet’s surface,
• With the right combination of materials, they reach significant thermal stability, enabling operation at or above 230°C (depending on the structure),
• The ability for custom shaping as well as adaptation to individual needs – neodymium magnets can be manufactured in multiple variants of geometries, which amplifies their functionality across industries,
• Wide application in advanced technical fields – they find application in computer drives, electromechanical systems, healthcare devices as well as technologically developed systems,
• Thanks to their concentrated strength, small magnets offer high magnetic performance, with minimal size,

Disadvantages of magnetic elements:

• They are fragile when subjected to a strong impact. If the magnets are exposed to mechanical hits, they should be placed in a steel housing. The steel housing, in the form of a holder, protects the magnet from breakage and additionally increases its overall robustness,
• They lose field intensity at extreme temperatures. Most neodymium magnets experience permanent reduction in strength when heated above 80°C (depending on the dimensions 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 common to use sealed magnets made of rubber for outdoor use,
• The use of a protective casing or external holder is recommended, since machining threads in neodymium magnets is difficult,
• Health risk related to magnet particles may arise, in case of ingestion, which is notable in the family environments. Moreover, miniature parts from these assemblies may complicate medical imaging if inside the body,
• Higher purchase price is an important factor to consider compared to ceramic magnets, especially in budget-sensitive applications

Maximum lifting capacity of the magnet – what affects it?

The given pulling force of the magnet corresponds to the maximum force, assessed in a perfect environment, namely:

• with the use of low-carbon steel plate acting as a magnetic yoke
• having a thickness of no less than 10 millimeters
• with a refined outer layer
• in conditions of no clearance
• under perpendicular detachment force
• in normal thermal conditions

Impact of factors on magnetic holding capacity in practice

The lifting capacity of a magnet is influenced by in practice key elements, ordered from most important to least significant:

• Air gap between the magnet and the plate, since even a very small distance (e.g. 0.5 mm) can cause 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.

* Lifting capacity was measured with the use of a smooth steel plate of optimal thickness (min. 20 mm), under perpendicular detachment force, in contrast under parallel forces the load capacity is reduced by as much as 5 times. Moreover, even a minimal clearance {between} the magnet and the plate decreases the load capacity.