SM 25x225 [2xM8] / N42 - magnetic separator

Advantages as well as disadvantages of rare earth magnets.

Besides their magnetic performance, neodymium magnets are valued for these benefits:

• Their strength is maintained, and after around 10 years it decreases only by ~1% (according to research),
• They do not lose their magnetic properties even under close interference source,
• A magnet with a shiny silver surface is more attractive,
• Neodymium magnets deliver maximum magnetic induction on a small surface, which increases force concentration,
• Through (appropriate) combination of ingredients, they can achieve high thermal strength, enabling operation at temperatures approaching 230°C and above...
• Possibility of custom creating and modifying to atypical needs,
• Key role in high-tech industry – they are utilized in HDD drives, motor assemblies, medical devices, also multitasking production systems.
• Relatively small size with high pulling force – neodymium magnets offer high power in tiny dimensions, which enables their usage in compact constructions

Disadvantages of NdFeB magnets:

• Susceptibility to cracking is one of their disadvantages. Upon intense impact they can break. We recommend keeping them in a special holder, which not only protects them against impacts but also increases their durability
• When exposed to high temperature, neodymium magnets suffer a drop in force. Often, when the temperature exceeds 80°C, their power decreases (depending on the size, as well as shape of the magnet). For those who need magnets for extreme conditions, we offer [AH] versions withstanding up to 230°C
• They oxidize in a humid environment - during use outdoors we advise using waterproof magnets e.g. in rubber, plastic
• Limited possibility of making threads in the magnet and complicated shapes - preferred is a housing - mounting mechanism.
• Health risk resulting from small fragments of magnets can be dangerous, in case of ingestion, which gains importance in the context of child safety. Additionally, tiny parts of these magnets can be problematic in diagnostics medical in case of swallowing.
• Higher cost of purchase is a significant factor to consider compared to ceramic magnets, especially in budget applications

Maximum lifting capacity of the magnet – what affects it?

The load parameter shown refers to the maximum value, measured under laboratory conditions, namely:

• with the use of a sheet made of special test steel, guaranteeing full magnetic saturation
• whose transverse dimension is min. 10 mm
• with an polished contact surface
• under conditions of ideal adhesion (surface-to-surface)
• under vertical force vector (90-degree angle)
• at standard ambient temperature

Lifting capacity in real conditions – factors

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

• Space between magnet and steel – even a fraction of a millimeter of separation (caused e.g. by varnish or dirt) drastically reduces the magnet efficiency, often by half at just 0.5 mm.
• Force direction – catalog parameter refers to pulling vertically. When applying parallel force, the magnet holds much less (often approx. 20-30% of maximum force).
• Base massiveness – too thin sheet does not accept the full field, causing part of the flux to be escaped into the air.
• Plate material – mild steel attracts best. Alloy steels reduce magnetic properties and lifting capacity.
• Surface finish – full contact is obtained only on smooth steel. Rough texture create air cushions, weakening the magnet.
• Heat – neodymium magnets have a negative temperature coefficient. When it is hot they lose power, and at low temperatures gain strength (up to a certain limit).

* Holding force was checked on a smooth steel plate of 20 mm thickness, when a perpendicular force was applied, in contrast under parallel forces the load capacity is reduced by as much as 5 times. Moreover, even a minimal clearance {between} the magnet and the plate reduces the holding force.