MP 25x8x5 / N38 - ring magnet

Strengths as well as weaknesses of NdFeB magnets.

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

• They have unchanged lifting capacity, and over more than 10 years their performance decreases symbolically – ~1% (in testing),
• They are extremely resistant to demagnetization induced by external magnetic fields,
• By using a decorative layer of silver, the element has an nice look,
• Magnets possess exceptionally strong magnetic induction on the surface,
• Due to their durability and thermal resistance, neodymium magnets can operate (depending on the shape) even at high temperatures reaching 230°C or more...
• Thanks to freedom in shaping and the capacity to adapt to unusual requirements,
• Key role in future technologies – they are commonly used in HDD drives, drive modules, precision medical tools, and technologically advanced constructions.
• Thanks to efficiency per cm³, small magnets offer high operating force, in miniature format,

Disadvantages of neodymium magnets:

• At very strong impacts they can crack, therefore we recommend placing them in steel cases. A metal housing provides additional protection against damage, as well as increases the magnet's durability.
• When exposed to high temperature, neodymium magnets suffer a drop in force. Often, when the temperature exceeds 80°C, their strength 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
• Due to the susceptibility of magnets to corrosion in a humid environment, we advise using waterproof magnets made of rubber, plastic or other material immune to moisture, in case of application outdoors
• Due to limitations in creating threads and complicated forms in magnets, we propose using a housing - magnetic holder.
• Potential hazard to health – tiny shards of magnets are risky, when accidentally swallowed, which gains importance in the context of child safety. Furthermore, small elements of these products can disrupt the diagnostic process medical when they are in the body.
• With budget limitations the cost of neodymium magnets is a challenge,

Highest magnetic holding force – what it depends on?

Breakaway force was determined for the most favorable conditions, taking into account:

• with the application of a sheet made of low-carbon steel, guaranteeing maximum field concentration
• possessing a thickness of minimum 10 mm to avoid saturation
• with a surface free of scratches
• with total lack of distance (no impurities)
• during pulling in a direction perpendicular to the mounting surface
• in temp. approx. 20°C

What influences lifting capacity in practice

It is worth knowing that the magnet holding may be lower influenced by elements below, in order of importance:

• Gap between surfaces – even a fraction of a millimeter of separation (caused e.g. by veneer or dirt) diminishes the magnet efficiency, often by half at just 0.5 mm.
• Load vector – maximum parameter is obtained only during perpendicular pulling. The force required to slide of the magnet along the plate is typically several times smaller (approx. 1/5 of the lifting capacity).
• Substrate thickness – for full efficiency, the steel must be sufficiently thick. Thin sheet restricts the attraction force (the magnet "punches through" it).
• Steel grade – ideal substrate is pure iron steel. Cast iron may have worse magnetic properties.
• Base smoothness – the more even the surface, the better the adhesion and higher the lifting capacity. Unevenness acts like micro-gaps.
• Temperature – heating the magnet results in weakening of induction. Check the thermal limit for a given model.

* Lifting capacity was assessed with the use of a smooth steel plate of suitable thickness (min. 20 mm), under perpendicular detachment force, in contrast under attempts to slide the magnet the load capacity is reduced by as much as fivefold. In addition, even a small distance {between} the magnet and the plate lowers the holding force.