MW 9x3 / N38 - cylindrical magnet

Strengths and weaknesses of neodymium magnets.

Besides their immense pulling force, neodymium magnets offer the following advantages:

• They have unchanged lifting capacity, and over more than ten years their performance decreases symbolically – ~1% (according to theory),
• Neodymium magnets prove to be highly resistant to loss of magnetic properties caused by magnetic disturbances,
• By applying a lustrous layer of gold, the element has an proper look,
• They show high magnetic induction at the operating surface, which affects their effectiveness,
• Due to their durability and thermal resistance, neodymium magnets are capable of operate (depending on the shape) even at high temperatures reaching 230°C or more...
• Considering the option of free forming and adaptation to unique needs, magnetic components can be modeled in a wide range of geometric configurations, which expands the range of possible applications,
• Fundamental importance in high-tech industry – they are used in HDD drives, brushless drives, medical devices, and multitasking production systems.
• Thanks to their power density, small magnets offer high operating force, with minimal size,

Disadvantages of neodymium magnets:

• They are fragile upon heavy impacts. To avoid cracks, it is worth securing magnets in special housings. Such protection not only shields the magnet but also improves its resistance to damage
• Neodymium magnets decrease 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
• Due to the susceptibility of magnets to corrosion in a humid environment, we recommend using waterproof magnets made of rubber, plastic or other material stable to moisture, when using outdoors
• Limited possibility of creating nuts in the magnet and complicated forms - preferred is a housing - magnet mounting.
• Possible danger related to microscopic parts of magnets are risky, in case of ingestion, which is particularly important in the context of child health protection. Furthermore, tiny parts of these devices are able to disrupt the diagnostic process medical after entering the body.
• High unit price – neodymium magnets cost more than other types of magnets (e.g. ferrite), which increases costs of application in large quantities

Maximum magnetic pulling force – what affects it?

Information about lifting capacity was determined for ideal contact conditions, taking into account:

• on a plate made of mild steel, effectively closing the magnetic field
• possessing a thickness of at least 10 mm to avoid saturation
• with an ideally smooth touching surface
• with zero gap (without coatings)
• for force applied at a right angle (in the magnet axis)
• in stable room temperature

Practical lifting capacity: influencing factors

Effective lifting capacity is affected by working environment parameters, including (from most important):

• Air gap (between the magnet and the plate), because even a tiny clearance (e.g. 0.5 mm) leads to a drastic drop in force by up to 50% (this also applies to paint, corrosion or dirt).
• Angle of force application – maximum parameter is available only during perpendicular pulling. The shear force of the magnet along the plate is usually many times smaller (approx. 1/5 of the lifting capacity).
• Substrate thickness – for full efficiency, the steel must be sufficiently thick. Paper-thin metal limits the lifting capacity (the magnet "punches through" it).
• Steel grade – the best choice is pure iron steel. Stainless steels may attract less.
• Base smoothness – the more even the plate, the better the adhesion and stronger the hold. Unevenness acts like micro-gaps.
• Thermal conditions – NdFeB sinters have a sensitivity to temperature. At higher temperatures they are weaker, and at low temperatures gain strength (up to a certain limit).

* Lifting capacity was determined using a polished steel plate of suitable thickness (min. 20 mm), under perpendicular detachment force, however under shearing force the holding force is lower. Moreover, even a small distance {between} the magnet’s surface and the plate decreases the holding force.