MW 8x20 / N38 - cylindrical magnet

Pros and cons of rare earth magnets.

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

• They virtually do not lose power, because even after 10 years the decline in efficiency is only ~1% (in laboratory conditions),
• Magnets perfectly resist against demagnetization caused by foreign field sources,
• Thanks to the smooth finish, the layer of Ni-Cu-Ni, gold-plated, or silver-plated gives an clean appearance,
• Magnetic induction on the working part of the magnet remains impressive,
• Due to their enhanced temperature resistance, they can operate (depending on the shape) even at temperatures up to 230°C or more,
• Possibility of individual forming and adapting to atypical applications,
• Wide application in electronics industry – they are used in mass storage devices, electromotive mechanisms, precision medical tools, as well as other advanced devices.
• Thanks to efficiency per cm³, small magnets offer high operating force, with minimal size,

Cons of neodymium magnets and proposals for their use:

• Brittleness is one of their disadvantages. Upon intense impact they can break. We recommend keeping them in a strong case, which not only secures them against impacts but also increases their durability
• Neodymium magnets decrease their strength 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
• 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 realizing threads and complicated forms in magnets, we propose using a housing - magnetic holder.
• Possible danger resulting from small fragments of magnets pose a threat, if swallowed, which becomes key in the context of child health protection. It is also worth noting that small elements of these products can complicate diagnosis medical after entering the body.
• High unit price – neodymium magnets are more expensive than other types of magnets (e.g. ferrite), which hinders application in large quantities

Best holding force of the magnet in ideal parameters – what it depends on?

The declared magnet strength concerns the limit force, measured under laboratory conditions, meaning:

• with the use of a yoke made of special test steel, guaranteeing full magnetic saturation
• whose transverse dimension is min. 10 mm
• with a plane cleaned and smooth
• without any air gap between the magnet and steel
• during pulling in a direction perpendicular to the mounting surface
• at room temperature

Impact of factors on magnetic holding capacity in practice

Real force impacted by working environment parameters, including (from most important):

• Clearance – the presence of any layer (rust, tape, air) acts as an insulator, which reduces capacity rapidly (even by 50% at 0.5 mm).
• Loading method – catalog parameter refers to detachment vertically. When applying parallel force, the magnet exhibits significantly lower power (typically approx. 20-30% of nominal force).
• Element thickness – to utilize 100% power, the steel must be adequately massive. Paper-thin metal restricts the lifting capacity (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 larger the contact zone and higher the lifting capacity. Roughness acts like micro-gaps.
• Heat – neodymium magnets have a sensitivity to temperature. At higher temperatures they lose power, and in frost gain strength (up to a certain limit).

* Lifting capacity was measured with the use of a polished steel plate of optimal 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 5 times. Additionally, even a slight gap {between} the magnet’s surface and the plate lowers the load capacity.