SM 19x225 [2xM6] / N50 - magnetic separator

Advantages as well as disadvantages of neodymium magnets NdFeB.

In addition to their pulling strength, neodymium magnets provide the following advantages:

• Their magnetic field is durable, and after around ten years, it drops only by ~1% (according to research),
• They are extremely resistant to demagnetization caused by external magnetic fields,
• The use of a mirror-like silver surface provides a refined finish,
• The outer field strength of the magnet shows remarkable magnetic properties,
• These magnets tolerate elevated temperatures, often exceeding 230°C, when properly designed (in relation to profile),
• The ability for accurate shaping or customization to specific needs – neodymium magnets can be manufactured in multiple variants of geometries, which amplifies their functionality across industries,
• Important function in cutting-edge sectors – they serve a purpose in hard drives, rotating machines, medical equipment or even other advanced devices,
• Thanks to their concentrated strength, small magnets offer high magnetic performance, in miniature format,

Disadvantages of rare earth magnets:

• They are fragile when subjected to a sudden 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 cracks and additionally increases its overall resistance,
• They lose magnetic force at extreme temperatures. Most neodymium magnets experience permanent decline 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, especially when used outside, we recommend using waterproof magnets, such as those made of plastic,
• The use of a protective casing or external holder is recommended, since machining multi-axis shapes in neodymium magnets is not feasible,
• Potential hazard from tiny pieces may arise, especially if swallowed, which is notable in the protection of children. Moreover, small elements from these devices can interfere with diagnostics if inside the body,
• In cases of mass production, neodymium magnet cost is a challenge,

Maximum magnetic pulling force – what affects it?

The given pulling force of the magnet means the maximum force, assessed in a perfect environment, specifically:

• with the use of low-carbon steel plate acting as a magnetic yoke
• of a thickness of at least 10 mm
• with a refined outer layer
• with no separation
• under perpendicular detachment force
• in normal thermal conditions

What influences lifting capacity in practice

In practice, the holding capacity of a magnet is affected by these factors, in descending order of importance:

• Air gap between the magnet and the plate, as 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 checked on the plate surface of 20 mm thickness, when a perpendicular force was applied, however under parallel forces the holding force is lower. Additionally, even a small distance {between} the magnet and the plate reduces the load capacity.