MW 35x5 / N38 - cylindrical magnet

Advantages as well as disadvantages of neodymium magnets NdFeB.

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

• Their magnetic field remains stable, and after around ten years, it drops only by ~1% (theoretically),
• They remain magnetized despite exposure to magnetic surroundings,
• Thanks to the polished finish and gold coating, they have an visually attractive appearance,
• Magnetic induction on the surface of these magnets is impressively powerful,
• Neodymium magnets are known for exceptionally strong magnetic induction and the ability to work at temperatures up to 230°C or higher (depending on the shape),
• The ability for accurate shaping and customization to individual needs – neodymium magnets can be manufactured in multiple variants of geometries, which extends the scope of their use cases,
• Significant impact in new technology industries – they are used in computer drives, electromechanical systems, clinical machines along with technologically developed systems,
• Compactness – despite their small size, they generate strong force, making them ideal for precision applications

Disadvantages of rare earth magnets:

• They are prone to breaking when subjected to a strong impact. If the magnets are exposed to shocks, we recommend in a metal holder. The steel housing, in the form of a holder, protects the magnet from breakage and enhances its overall robustness,
• They lose field intensity at extreme temperatures. Most neodymium magnets experience permanent degradation 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,
• They rust in a moist environment. For outdoor use, we recommend using moisture-resistant magnets, such as those made of non-metallic materials,
• Limited ability to create internal holes in the magnet – the use of a external casing is recommended,
• Possible threat related to magnet particles may arise, especially if swallowed, which is important in the family environments. It should also be noted that minuscule fragments from these magnets can disrupt scanning if inside the body,
• In cases of large-volume purchasing, neodymium magnet cost is a challenge,

Maximum magnetic pulling force – what it depends on?

The given strength of the magnet corresponds to the optimal strength, determined under optimal conditions, specifically:

• 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
• in conditions of no clearance
• with vertical force applied
• at room temperature

Determinants of lifting force in real conditions

The lifting capacity of a magnet is determined by in practice the following factors, ordered from most important to least significant:

• Air gap between the magnet and the plate, as 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 checked on a smooth steel plate of 20 mm thickness, when a perpendicular force was applied, in contrast under attempts to slide the magnet the load capacity is reduced by as much as 5 times. In addition, even a slight gap {between} the magnet’s surface and the plate lowers the lifting capacity.