MW 40x30 / N38 - cylindrical magnet

Advantages and disadvantages of neodymium magnets NdFeB.

Apart from their consistent magnetic energy, neodymium magnets have these key benefits:

• They retain their attractive force for around 10 years – the drop is just ~1% (according to analyses),
• They are highly resistant to demagnetization caused by external magnetic fields,
• Thanks to the polished finish and gold coating, they have an aesthetic appearance,
• They possess significant magnetic force measurable at the magnet’s surface,
• Thanks to their enhanced temperature resistance, they can operate (depending on the form) even at temperatures up to 230°C or more,
• The ability for accurate shaping as well as adaptation to custom needs – neodymium magnets can be manufactured in multiple variants of geometries, which enhances their versatility in applications,
• Significant impact in cutting-edge sectors – they are used in hard drives, electric motors, clinical machines or even high-tech tools,
• Thanks to their power density, small magnets offer high magnetic performance, while occupying minimal space,

Disadvantages of neodymium magnets:

• They can break when subjected to a sudden impact. If the magnets are exposed to mechanical hits, it is advisable to use in a metal holder. The steel housing, in the form of a holder, protects the magnet from damage , and at the same time reinforces its overall durability,
• They lose magnetic force at elevated temperatures. Most neodymium magnets experience permanent loss 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 humid environment, especially when used outside, we recommend using sealed magnets, such as those made of plastic,
• The use of a protective casing or external holder is recommended, since machining threads in neodymium magnets is risky,
• Potential hazard related to magnet particles may arise, when consumed by mistake, which is crucial in the health of young users. It should also be noted that miniature parts from these products have the potential to complicate medical imaging once in the system,
• In cases of large-volume purchasing, neodymium magnet cost may not be economically viable,

Breakaway strength of the magnet in ideal conditions – what contributes to it?

The given strength of the magnet means the optimal strength, calculated in ideal conditions, specifically:

• using a steel plate with low carbon content, acting as a magnetic circuit closure
• having a thickness of no less than 10 millimeters
• with a smooth surface
• with zero air gap
• under perpendicular detachment force
• at room temperature

Determinants of practical lifting force of a magnet

In practice, the holding capacity of a magnet is conditioned by these factors, from crucial to less important:

• 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 the plate surface of 20 mm thickness, when the force acted perpendicularly, however under attempts to slide the magnet the holding force is lower. In addition, even a slight gap {between} the magnet’s surface and the plate decreases the lifting capacity.