SMZR 25x150 / N52 - magnetic separator with handle

Pros and cons of rare earth magnets.

Besides their high retention, neodymium magnets are valued for these benefits:

• Their strength remains stable, and after around 10 years it drops only by ~1% (theoretically),
• They have excellent resistance to magnetism drop as a result of external fields,
• Thanks to the smooth finish, the layer of nickel, gold, or silver gives an visually attractive appearance,
• Magnetic induction on the working layer of the magnet is extremely intense,
• Due to their durability and thermal resistance, neodymium magnets are capable of operate (depending on the shape) even at high temperatures reaching 230°C or more...
• Thanks to versatility in shaping and the capacity to modify to client solutions,
• Huge importance in modern industrial fields – they are commonly used in hard drives, electric motors, diagnostic systems, as well as complex engineering applications.
• Thanks to their power density, small magnets offer high operating force, in miniature format,

Disadvantages of neodymium magnets:

• To avoid cracks upon strong impacts, we recommend using special steel holders. Such a solution secures the magnet and simultaneously improves its durability.
• NdFeB magnets demagnetize when exposed to high temperatures. After reaching 80°C, many of them experience permanent drop of strength (a factor is the shape as well as dimensions of the magnet). We offer magnets specially adapted to work at temperatures up to 230°C marked [AH], which are extremely resistant to heat
• Due to the susceptibility of magnets to corrosion in a humid environment, we recommend using waterproof magnets made of rubber, plastic or other material resistant to moisture, in case of application outdoors
• We suggest a housing - magnetic mount, due to difficulties in producing nuts inside the magnet and complex shapes.
• Health risk resulting from small fragments of magnets can be dangerous, in case of ingestion, which gains importance in the context of child safety. It is also worth noting that small components of these devices are able to disrupt the diagnostic process medical in case of swallowing.
• Due to complex production process, their price is relatively high,

Magnetic strength at its maximum – what it depends on?

Information about lifting capacity was determined for optimal configuration, including:

• using a plate made of low-carbon steel, functioning as a magnetic yoke
• whose transverse dimension is min. 10 mm
• characterized by even structure
• under conditions of ideal adhesion (surface-to-surface)
• for force applied at a right angle (pull-off, not shear)
• at room temperature

Lifting capacity in practice – influencing factors

Holding efficiency is affected by specific conditions, including (from priority):

• Space between surfaces – even a fraction of a millimeter of separation (caused e.g. by varnish or dirt) diminishes the magnet efficiency, often by half at just 0.5 mm.
• Pull-off angle – note that the magnet holds strongest perpendicularly. Under shear forces, the capacity drops drastically, often to levels of 20-30% of the maximum value.
• Metal thickness – the thinner the sheet, the weaker the hold. Magnetic flux passes through the material instead of generating force.
• Chemical composition of the base – mild steel gives the best results. Higher carbon content reduce magnetic permeability and lifting capacity.
• Surface condition – ground elements guarantee perfect abutment, which improves force. Uneven metal weaken the grip.
• Thermal factor – high temperature reduces magnetic field. Exceeding the limit temperature can permanently demagnetize the magnet.

* Holding force was checked on a smooth steel plate of 20 mm thickness, when a perpendicular force was applied, however under attempts to slide the magnet the load capacity is reduced by as much as fivefold. Additionally, even a minimal clearance {between} the magnet and the plate reduces the lifting capacity.