SM 32x175 [2xM8] / N52 - magnetic separator

Advantages as well as disadvantages of NdFeB magnets.

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

• They have stable power, and over around ten years their attraction force decreases symbolically – ~1% (according to theory),
• They possess excellent resistance to weakening of magnetic properties due to external magnetic sources,
• Thanks to the smooth finish, the coating of Ni-Cu-Ni, gold, or silver gives an modern appearance,
• Neodymium magnets achieve maximum magnetic induction on a contact point, which ensures high operational effectiveness,
• Through (appropriate) combination of ingredients, they can achieve high thermal strength, allowing for functioning at temperatures reaching 230°C and above...
• Thanks to versatility in constructing and the capacity to modify to complex applications,
• Significant place in high-tech industry – they serve a role in HDD drives, drive modules, medical equipment, as well as technologically advanced constructions.
• Compactness – despite small sizes they offer powerful magnetic field, making them ideal for precision applications

What to avoid - cons of neodymium magnets and proposals for their use:

• To avoid cracks under impact, we suggest using special steel housings. Such a solution secures the magnet and simultaneously increases its durability.
• Neodymium magnets lose their power under the influence of heating. As soon as 80°C is exceeded, many of them start losing their force. Therefore, we recommend our special magnets marked [AH], which maintain durability even at temperatures up to 230°C
• When exposed to humidity, magnets start to rust. For applications outside, it is recommended to use protective magnets, such as magnets in rubber or plastics, which secure oxidation as well as corrosion.
• Limited possibility of producing nuts in the magnet and complex forms - recommended is casing - magnetic holder.
• Potential hazard resulting from small fragments of magnets pose a threat, if swallowed, which is particularly important in the aspect of protecting the youngest. It is also worth noting that small components of these magnets are able to disrupt the diagnostic process medical when they are in the body.
• High unit price – neodymium magnets are more expensive than other types of magnets (e.g. ferrite), which hinders application in large quantities

Maximum magnetic pulling force – what contributes to it?

The lifting capacity listed is a result of laboratory testing executed under standard conditions:

• using a sheet made of low-carbon steel, functioning as a ideal flux conductor
• possessing a thickness of minimum 10 mm to ensure full flux closure
• with an polished contact surface
• with direct contact (no coatings)
• during detachment in a direction vertical to the plane
• in stable room temperature

Key elements affecting lifting force

In real-world applications, the actual holding force depends on a number of factors, presented from crucial:

• Distance – existence of foreign body (paint, tape, gap) acts as an insulator, which reduces power steeply (even by 50% at 0.5 mm).
• Angle of force application – maximum parameter is available only during perpendicular pulling. The resistance to sliding of the magnet along the plate is typically many times lower (approx. 1/5 of the lifting capacity).
• Plate thickness – insufficiently thick steel causes magnetic saturation, causing part of the flux to be escaped into the air.
• Chemical composition of the base – mild steel gives the best results. Higher carbon content lower magnetic permeability and holding force.
• Plate texture – ground elements ensure maximum contact, which improves field saturation. Rough surfaces weaken the grip.
• Thermal conditions – 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 tested on a smooth steel plate of 20 mm thickness, when the force acted perpendicularly, however under attempts to slide the magnet the lifting capacity is smaller. In addition, even a small distance {between} the magnet and the plate reduces the lifting capacity.