SM 18x125 [2xM5] / N42 - magnetic separator

Pros and cons of NdFeB magnets.

Besides their exceptional field intensity, neodymium magnets offer the following advantages:

• They have constant strength, and over around ten years their attraction force decreases symbolically – ~1% (according to theory),
• They are extremely resistant to demagnetization induced by external magnetic fields,
• A magnet with a shiny nickel surface has better aesthetics,
• The surface of neodymium magnets generates a powerful magnetic field – this is a key feature,
• Thanks to resistance to high temperature, they can operate (depending on the shape) even at temperatures up to 230°C and higher...
• In view of the option of accurate molding and customization to unique requirements, NdFeB magnets can be created in a broad palette of forms and dimensions, which makes them more universal,
• Wide application in electronics industry – they find application in computer drives, drive modules, medical equipment, also industrial machines.
• Compactness – despite small sizes they generate large force, making them ideal for precision applications

Disadvantages of NdFeB magnets:

• Susceptibility to cracking is one of their disadvantages. Upon intense impact they can fracture. We advise keeping them in a strong case, which not only protects them against impacts but also increases their durability
• We warn that neodymium magnets can reduce their strength at high temperatures. To prevent this, we suggest our specialized [AH] magnets, which work effectively even at 230°C.
• They oxidize in a humid environment - during use outdoors we suggest using waterproof magnets e.g. in rubber, plastic
• We suggest cover - magnetic mount, due to difficulties in producing nuts inside the magnet and complicated forms.
• Possible danger to health – tiny shards of magnets pose a threat, if swallowed, which is particularly important in the context of child safety. Additionally, small components of these magnets can disrupt the diagnostic process medical in case of swallowing.
• Higher cost of purchase is one of the disadvantages compared to ceramic magnets, especially in budget applications

Maximum lifting force for a neodymium magnet – what affects it?

The declared magnet strength represents the maximum value, recorded under ideal test conditions, meaning:

• using a plate made of mild steel, acting as a magnetic yoke
• possessing a thickness of min. 10 mm to avoid saturation
• with a surface free of scratches
• without any insulating layer between the magnet and steel
• for force acting at a right angle (in the magnet axis)
• at standard ambient temperature

Magnet lifting force in use – key factors

During everyday use, the actual holding force results from many variables, ranked from crucial:

• Clearance – existence of foreign body (rust, dirt, gap) interrupts the magnetic circuit, which lowers capacity steeply (even by 50% at 0.5 mm).
• Direction of force – highest force is obtained only during pulling at a 90° angle. The shear force of the magnet along the plate is typically many times lower (approx. 1/5 of the lifting capacity).
• Wall thickness – thin material does not allow full use of the magnet. Part of the magnetic field passes through the material instead of generating force.
• Steel type – mild steel gives the best results. Alloy steels lower magnetic properties and lifting capacity.
• Surface finish – full contact is possible only on polished steel. Any scratches and bumps reduce the real contact area, weakening the magnet.
• Temperature influence – high temperature weakens magnetic field. Exceeding the limit temperature can permanently damage the magnet.

* Holding force was tested on a smooth steel plate of 20 mm thickness, when the force acted perpendicularly, however under parallel forces the load capacity is reduced by as much as 75%. Additionally, even a small distance {between} the magnet’s surface and the plate decreases the holding force.