SM 25x275 [2xM8] / N52 - magnetic separator

Advantages and disadvantages of rare earth magnets.

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

• They do not lose magnetism, even during around ten years – the drop in power is only ~1% (based on measurements),
• Magnets perfectly defend themselves against demagnetization caused by ambient magnetic noise,
• By using a shiny layer of nickel, the element has an professional look,
• They show high magnetic induction at the operating surface, which improves attraction properties,
• Neodymium magnets are characterized by extremely high magnetic induction on the magnet surface and can function (depending on the shape) even at a temperature of 230°C or more...
• Possibility of exact forming and adjusting to concrete applications,
• Versatile presence in future technologies – they are used in hard drives, drive modules, diagnostic systems, as well as modern systems.
• Compactness – despite small sizes they offer powerful magnetic field, making them ideal for precision applications

Drawbacks and weaknesses of neodymium magnets and proposals for their use:

• Brittleness is one of their disadvantages. Upon intense impact they can fracture. We advise keeping them in a special holder, which not only protects them against impacts but also increases their durability
• We warn that neodymium magnets can reduce their power at high temperatures. To prevent this, we suggest our specialized [AH] magnets, which work effectively even at 230°C.
• They rust in a humid environment - during use outdoors we recommend using waterproof magnets e.g. in rubber, plastic
• Due to limitations in realizing threads and complex shapes in magnets, we recommend using casing - magnetic mechanism.
• Possible danger to health – tiny shards of magnets pose a threat, in case of ingestion, which is particularly important in the context of child health protection. Furthermore, small components of these devices are able to complicate diagnosis medical in case of swallowing.
• High unit price – neodymium magnets have a higher price than other types of magnets (e.g. ferrite), which hinders application in large quantities

Maximum magnetic pulling force – what affects it?

The force parameter is a result of laboratory testing performed under specific, ideal conditions:

• with the application of a yoke made of special test steel, guaranteeing full magnetic saturation
• possessing a thickness of min. 10 mm to avoid saturation
• with an ground contact surface
• without any air gap between the magnet and steel
• under axial force direction (90-degree angle)
• at standard ambient temperature

Determinants of practical lifting force of a magnet

In real-world applications, the actual holding force is determined by many variables, ranked from most significant:

• Space between surfaces – even a fraction of a millimeter of distance (caused e.g. by veneer or dirt) drastically reduces the magnet efficiency, often by half at just 0.5 mm.
• Force direction – declared lifting capacity refers to detachment vertically. When attempting to slide, the magnet holds much less (typically approx. 20-30% of maximum force).
• Base massiveness – too thin steel does not accept the full field, causing part of the flux to be escaped into the air.
• Material composition – not every steel attracts identically. Alloy additives worsen the interaction with the magnet.
• Surface structure – the more even the surface, the better the adhesion and stronger the hold. Roughness acts like micro-gaps.
• Thermal factor – high temperature weakens pulling force. Exceeding the limit temperature can permanently damage the magnet.

* Lifting capacity testing was carried out on a smooth plate of suitable thickness, under a perpendicular pulling force, however under attempts to slide the magnet the holding force is lower. Additionally, even a slight gap {between} the magnet’s surface and the plate decreases the lifting capacity.