SM 32x150 [2xM8] / N52 - magnetic separator

Advantages and disadvantages of neodymium magnets NdFeB.

In addition to their immense field intensity, neodymium magnets offer the following advantages:

• They virtually do not lose power, because even after 10 years, the performance loss is only ~1% (according to literature),
• Their ability to resist magnetic interference from external fields is impressive,
• The use of a mirror-like nickel surface provides a smooth finish,
• They possess strong magnetic force measurable at the magnet’s surface,
• These magnets tolerate elevated temperatures, often exceeding 230°C, when properly designed (in relation to build),
• The ability for custom shaping or adjustment to specific needs – neodymium magnets can be manufactured in multiple variants of geometries, which extends the scope of their use cases,
• Wide application in cutting-edge sectors – they are utilized in computer drives, electric drives, medical equipment or even sophisticated instruments,
• Relatively small size with high magnetic force – neodymium magnets offer intense magnetic field in small dimensions, which makes them ideal in miniature devices

Disadvantages of NdFeB magnets:

• They may fracture when subjected to a heavy impact. If the magnets are exposed to mechanical hits, they should be placed in a protective case. The steel housing, in the form of a holder, protects the magnet from damage while also reinforces its overall durability,
• They lose strength at high temperatures. Most neodymium magnets experience permanent loss in strength when heated above 80°C (depending on the form 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. For outdoor use, we recommend using moisture-resistant magnets, such as those made of rubber,
• The use of a protective casing or external holder is recommended, since machining multi-axis shapes in neodymium magnets is restricted,
• Health risk due to small fragments may arise, in case of ingestion, which is significant in the context of child safety. It should also be noted that miniature parts from these magnets can hinder health screening once in the system,
• Higher purchase price is one of the drawbacks compared to ceramic magnets, especially in budget-sensitive applications

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

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

• using a steel plate with low carbon content, acting as a magnetic circuit closure
• of a thickness of at least 10 mm
• with a refined outer layer
• with zero air gap
• with vertical force applied
• at room temperature

Lifting capacity in practice – influencing factors

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

• Air gap between the magnet and the plate, because 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 a perpendicular force was applied, whereas under parallel forces the load capacity is reduced by as much as 5 times. Moreover, even a minimal clearance {between} the magnet’s surface and the plate lowers the holding force.