MW 20x5 / N38 - cylindrical magnet

Strengths and weaknesses of NdFeB magnets.

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

• They virtually do not lose strength, because even after ten years the decline in efficiency is only ~1% (in laboratory conditions),
• Magnets effectively protect themselves against demagnetization caused by foreign field sources,
• Thanks to the metallic finish, the layer of nickel, gold-plated, or silver gives an visually attractive appearance,
• Neodymium magnets deliver maximum magnetic induction on a small surface, which ensures high operational effectiveness,
• Thanks to resistance to high temperature, they are capable of working (depending on the shape) even at temperatures up to 230°C and higher...
• Thanks to flexibility in forming and the ability to modify to client solutions,
• Huge importance in advanced technology sectors – they are used in mass storage devices, electric drive systems, precision medical tools, and other advanced devices.
• Thanks to their power density, small magnets offer high operating force, occupying minimum space,

Cons of neodymium magnets: weaknesses and usage proposals

• They are prone to damage upon too strong impacts. To avoid cracks, it is worth protecting magnets using a steel holder. Such protection not only shields the magnet but also increases its resistance to damage
• When exposed to high temperature, neodymium magnets experience a drop in force. Often, when the temperature exceeds 80°C, their power decreases (depending on the size and 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 usually rust. To use them in conditions outside, it is recommended to use protective magnets, such as magnets in rubber or plastics, which prevent oxidation as well as corrosion.
• We suggest a housing - magnetic holder, due to difficulties in creating nuts inside the magnet and complicated forms.
• Potential hazard resulting from small fragments of magnets can be dangerous, if swallowed, which gains importance in the context of child health protection. Additionally, small components of these magnets are able to be problematic in diagnostics medical when they are in the body.
• With mass production the cost of neodymium magnets can be a barrier,

Optimal lifting capacity of a neodymium magnet – what contributes to it?

The load parameter shown represents the peak performance, obtained under laboratory conditions, specifically:

• on a base made of structural steel, effectively closing the magnetic field
• possessing a massiveness of at least 10 mm to ensure full flux closure
• with an polished contact surface
• with total lack of distance (no paint)
• for force applied at a right angle (in the magnet axis)
• at standard ambient temperature

Determinants of lifting force in real conditions

Holding efficiency impacted by working environment parameters, mainly (from most important):

• Air gap (betwixt the magnet and the metal), as even a microscopic clearance (e.g. 0.5 mm) results in a reduction in force by up to 50% (this also applies to varnish, corrosion or dirt).
• Pull-off angle – remember that the magnet holds strongest perpendicularly. Under shear forces, the capacity drops significantly, often to levels of 20-30% of the nominal value.
• Substrate thickness – to utilize 100% power, the steel must be adequately massive. Paper-thin metal limits the lifting capacity (the magnet "punches through" it).
• Material type – ideal substrate is high-permeability steel. Stainless steels may attract less.
• Surface condition – ground elements guarantee perfect abutment, which increases force. Uneven metal weaken the grip.
• Temperature influence – high temperature weakens pulling force. Exceeding the limit temperature can permanently damage the magnet.

* Lifting capacity was assessed using a polished steel plate of suitable thickness (min. 20 mm), under vertically applied force, whereas under attempts to slide the magnet the lifting capacity is smaller. Additionally, even a small distance {between} the magnet and the plate lowers the load capacity.