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

Advantages as well as disadvantages of rare earth magnets.

Apart from their superior magnetism, neodymium magnets have these key benefits:

• They do not lose power, even during around ten years – the reduction in power is only ~1% (based on measurements),
• They maintain their magnetic properties even under external field action,
• Thanks to the smooth finish, the surface of Ni-Cu-Ni, gold-plated, or silver gives an clean appearance,
• Magnetic induction on the surface of the magnet remains impressive,
• With the right combination of materials, they reach excellent thermal stability, enabling operation at or above 230°C (depending on the form),
• Possibility of precise forming and adapting to specific conditions,
• Wide application in electronics industry – they serve a role in computer drives, electromotive mechanisms, precision medical tools, 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 strong case, which not only secures them against impacts but also increases their durability
• When exposed to high temperature, neodymium magnets experience a drop in power. 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
• 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 prevent oxidation and corrosion.
• Due to limitations in creating threads and complex shapes in magnets, we recommend using casing - magnetic mechanism.
• Potential hazard related to microscopic parts of magnets are risky, if swallowed, which becomes key in the context of child safety. It is also worth noting that tiny parts of these magnets can be problematic in diagnostics medical in case of swallowing.
• Higher cost of purchase is one of the disadvantages compared to ceramic magnets, especially in budget applications

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

Holding force of 0 kg is a measurement result executed under standard conditions:

• using a base made of low-carbon steel, functioning as a magnetic yoke
• with a cross-section of at least 10 mm
• with a surface free of scratches
• without the slightest clearance between the magnet and steel
• for force applied at a right angle (pull-off, not shear)
• at conditions approx. 20°C

Practical aspects of lifting capacity – factors

Real force is affected by working environment parameters, mainly (from priority):

• Distance – existence of any layer (paint, tape, gap) interrupts the magnetic circuit, which reduces capacity steeply (even by 50% at 0.5 mm).
• Pull-off angle – note that the magnet holds strongest perpendicularly. Under shear forces, the capacity drops drastically, often to levels of 20-30% of the nominal value.
• Element thickness – for full efficiency, the steel must be sufficiently thick. Paper-thin metal limits the lifting capacity (the magnet "punches through" it).
• Steel type – low-carbon steel gives the best results. Alloy admixtures reduce magnetic permeability and holding force.
• Surface condition – ground elements ensure maximum contact, which increases force. Rough surfaces reduce efficiency.
• Thermal factor – high temperature reduces magnetic field. Too high temperature can permanently demagnetize the magnet.

* Holding force was checked on a smooth steel plate of 20 mm thickness, when the force acted perpendicularly, whereas under attempts to slide the magnet the holding force is lower. Moreover, even a slight gap {between} the magnet’s surface and the plate lowers the holding force.