MW 15x3 / N38 - cylindrical magnet

Advantages as well as disadvantages of neodymium magnets NdFeB.

In addition to their magnetic efficiency, neodymium magnets provide the following advantages:

• They have unchanged lifting capacity, and over nearly 10 years their performance decreases symbolically – ~1% (according to theory),
• They show strong resistance to demagnetization from outside magnetic sources,
• By applying a bright layer of silver, the element gains a sleek look,
• They exhibit extremely high levels of magnetic induction near the outer area of the magnet,
• These magnets tolerate elevated temperatures, often exceeding 230°C, when properly designed (in relation to profile),
• Thanks to the possibility in shaping and the capability to adapt to individual requirements, neodymium magnets can be created in different geometries, which expands their application range,
• Wide application in modern technologies – they are used in hard drives, electric motors, medical equipment or even technologically developed systems,
• Relatively small size with high magnetic force – neodymium magnets offer intense magnetic field in small dimensions, which makes them useful in compact constructions

Disadvantages of NdFeB magnets:

• They may fracture when subjected to a heavy impact. If the magnets are exposed to mechanical hits, it is suggested to place them in a protective case. The steel housing, in the form of a holder, protects the magnet from damage and reinforces its overall robustness,
• They lose field intensity at increased temperatures. Most neodymium magnets experience permanent degradation in strength when heated above 80°C (depending on the geometry 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 recommended to use sealed magnets made of plastic for outdoor use,
• Limited ability to create internal holes in the magnet – the use of a mechanical support is recommended,
• Safety concern related to magnet particles may arise, especially if swallowed, which is significant in the health of young users. It should also be noted that small elements from these devices might disrupt scanning when ingested,
• Due to expensive raw materials, their cost is considerably higher,

Magnetic strength at its maximum – what it depends on?

The given pulling force of the magnet represents the maximum force, assessed in a perfect environment, that is:

• with the use of low-carbon steel plate serving as a magnetic yoke
• with a thickness of minimum 10 mm
• with a polished side
• with no separation
• with vertical force applied
• at room temperature

Impact of factors on magnetic holding capacity in practice

In practice, the holding capacity of a magnet is conditioned by these factors, arranged from the most important to the least relevant:

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

* Lifting capacity was assessed with the use of a smooth steel plate of optimal thickness (min. 20 mm), under vertically applied force, whereas under shearing force the holding force is lower. In addition, even a slight gap {between} the magnet’s surface and the plate lowers the holding force.