SM 25x250 [2xM8] / N42 - magnetic separator

Pros and cons of neodymium magnets.

In addition to their long-term stability, neodymium magnets provide the following advantages:

• They retain attractive force for around ten years – the drop is just ~1% (based on simulations),
• They are extremely resistant to demagnetization induced by presence of other magnetic fields,
• A magnet with a smooth gold surface has better aesthetics,
• Magnetic induction on the working layer of the magnet is extremely intense,
• Thanks to resistance to high temperature, they can operate (depending on the form) even at temperatures up to 230°C and higher...
• Possibility of individual machining as well as adapting to atypical applications,
• Huge importance in high-tech industry – they find application in hard drives, electric drive systems, advanced medical instruments, also multitasking production systems.
• Compactness – despite small sizes they offer powerful magnetic field, making them ideal for precision applications

Disadvantages of NdFeB magnets:

• Susceptibility to cracking is one of their disadvantages. Upon strong impact they can break. We recommend keeping them in a steel housing, which not only secures them against impacts but also increases their durability
• NdFeB magnets demagnetize when exposed to high temperatures. After reaching 80°C, many of them experience permanent weakening of power (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
• They oxidize in a humid environment - during use outdoors we advise using waterproof magnets e.g. in rubber, plastic
• We suggest a housing - magnetic mount, due to difficulties in producing nuts inside the magnet and complex forms.
• Health risk related to microscopic parts of magnets are risky, when accidentally swallowed, which gains importance in the aspect of protecting the youngest. Furthermore, tiny parts of these devices can be problematic in diagnostics medical when they are in the body.
• Due to expensive raw materials, their price is relatively high,

Detachment force of the magnet in optimal conditions – what affects it?

The force parameter is a result of laboratory testing performed under standard conditions:

• with the application of a yoke made of special test steel, ensuring full magnetic saturation
• possessing a thickness of minimum 10 mm to ensure full flux closure
• characterized by even structure
• with direct contact (no paint)
• for force acting at a right angle (pull-off, not shear)
• at temperature approx. 20 degrees Celsius

Impact of factors on magnetic holding capacity in practice

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

• Distance – the presence of foreign body (paint, tape, gap) acts as an insulator, which lowers power steeply (even by 50% at 0.5 mm).
• Force direction – catalog parameter refers to pulling vertically. When slipping, the magnet holds much less (often approx. 20-30% of nominal force).
• Element thickness – to utilize 100% power, the steel must be sufficiently thick. Thin sheet restricts the lifting capacity (the magnet "punches through" it).
• Material type – ideal substrate is pure iron steel. Hardened steels may have worse magnetic properties.
• Base smoothness – the smoother and more polished the surface, the larger the contact zone and higher the lifting capacity. Roughness creates an air distance.
• Temperature – heating the magnet causes a temporary drop of induction. It is worth remembering the maximum operating temperature for a given model.

* Lifting capacity was measured using a polished steel plate of suitable thickness (min. 20 mm), under perpendicular pulling force, whereas under attempts to slide the magnet the load capacity is reduced by as much as fivefold. Additionally, even a slight gap {between} the magnet and the plate lowers the lifting capacity.