MW 12x6 / N38 - cylindrical magnet

Advantages as well as disadvantages of neodymium magnets NdFeB.

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

• They retain their full power for nearly ten years – the loss is just ~1% (in theory),
• They show superior resistance to demagnetization from outside magnetic sources,
• Because of the lustrous layer of nickel, the component looks high-end,
• They possess significant magnetic force measurable at the magnet’s surface,
• Neodymium magnets are known for very high magnetic induction and the ability to work at temperatures up to 230°C or higher (depending on the magnetic form),
• The ability for custom shaping as well as adjustment to custom needs – neodymium magnets can be manufactured in many forms and dimensions, which amplifies their functionality across industries,
• Key role in modern technologies – they serve a purpose in computer drives, electromechanical systems, healthcare devices or even sophisticated instruments,
• Thanks to their efficiency per volume, small magnets offer high magnetic performance, in miniature format,

Disadvantages of rare earth magnets:

• They are fragile when subjected to a strong impact. If the magnets are exposed to external force, they should be placed in a metal holder. The steel housing, in the form of a holder, protects the magnet from damage while also increases its overall durability,
• Magnets lose pulling force when exposed to temperatures exceeding 80°C. In most cases, this leads to irreversible power drop (influenced by the magnet’s profile). To address this, we provide [AH] models with superior thermal resistance, able to operate even at 230°C or more,
• They rust in a moist environment – during outdoor use, we recommend using encapsulated magnets, such as those made of non-metallic materials,
• The use of a protective casing or external holder is recommended, since machining threads in neodymium magnets is difficult,
• Possible threat from tiny pieces may arise, when consumed by mistake, which is important in the health of young users. Additionally, minuscule fragments from these products may disrupt scanning once in the system,
• High unit cost – neodymium magnets are costlier than other types of magnets (e.g., ferrite), which increases the cost of large-scale applications

Highest magnetic holding force – what it depends on?

The given strength of the magnet means the optimal strength, assessed in ideal conditions, namely:

• with mild steel, used as a magnetic flux conductor
• with a thickness of minimum 10 mm
• with a smooth surface
• with zero air gap
• in a perpendicular direction of force
• in normal thermal conditions

Lifting capacity in real conditions – factors

The lifting capacity of a magnet is determined by in practice the following factors, from primary to secondary:

• Air gap between the magnet and the plate, because 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.

* Holding force was measured on a smooth steel plate of 20 mm thickness, when the force acted perpendicularly, however under parallel forces the holding force is lower. In addition, even a minimal clearance {between} the magnet’s surface and the plate decreases the load capacity.