UMC 60x9/5x15 / N38 - cylindrical magnetic holder

Advantages and disadvantages of neodymium magnets NdFeB.

In addition to their magnetic efficiency, neodymium magnets provide the following advantages:

• They have unchanged lifting capacity, and over nearly ten years their performance decreases symbolically – ~1% (according to theory),
• They are extremely resistant to demagnetization caused by external field interference,
• In other words, due to the metallic gold coating, the magnet obtains an professional appearance,
• Magnetic induction on the surface of these magnets is impressively powerful,
• Thanks to their enhanced temperature resistance, they can operate (depending on the shape) even at temperatures up to 230°C or more,
• The ability for accurate shaping or adaptation to individual needs – neodymium magnets can be manufactured in multiple variants of geometries, which extends the scope of their use cases,
• Key role in modern technologies – they find application in data storage devices, electric drives, clinical machines as well as high-tech tools,
• Thanks to their efficiency per volume, small magnets offer high magnetic performance, in miniature format,

Disadvantages of NdFeB magnets:

• They can break when subjected to a heavy impact. If the magnets are exposed to shocks, it is suggested to place them in a protective enclosure. The steel housing, in the form of a holder, protects the magnet from cracks , and at the same time strengthens its overall resistance,
• High temperatures may significantly reduce the field efficiency of neodymium magnets. Typically, above 80°C, they experience permanent loss in performance (depending on height). To prevent this, we offer heat-resistant magnets marked [AH], capable of working up to 230°C, which makes them perfect for high-temperature use,
• Due to corrosion risk in humid conditions, it is recommended to use sealed magnets made of rubber for outdoor use,
• Limited ability to create precision features in the magnet – the use of a external casing is recommended,
• Potential hazard due to small fragments may arise, especially if swallowed, which is notable in the family environments. Furthermore, minuscule fragments from these magnets may hinder health screening if inside the body,
• In cases of mass production, neodymium magnet cost is a challenge,

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

The given holding capacity of the magnet means the highest holding force, measured under optimal conditions, specifically:

• with the use of low-carbon steel plate serving as a magnetic yoke
• with a thickness of minimum 10 mm
• with a smooth surface
• with no separation
• in a perpendicular direction of force
• at room temperature

Lifting capacity in real conditions – factors

Practical lifting force is dependent on factors, listed from the most critical to the less significant:

• Air gap between the magnet and the plate, because even a very small distance (e.g. 0.5 mm) can cause a drop in lifting force of up to 50%.
• Direction of applied force, because the maximum lifting capacity is achieved under perpendicular application. The force required to slide the magnet along the plate is usually several times lower.
• Thickness of the plate, as a plate that is too thin causes part of the magnetic flux not to be used and to remain wasted in the air.
• Material of the plate, because higher carbon content lowers holding force, while higher iron content increases it. The best choice is steel with high magnetic permeability and high saturation induction.
• Surface of the plate, because the more smooth and polished it is, the better the contact and consequently the greater the magnetic saturation.
• Operating temperature, since all permanent magnets have a negative temperature coefficient. This means that at high temperatures they are weaker, while at sub-zero temperatures they become slightly stronger.

* Lifting capacity was determined by applying a smooth steel plate of optimal thickness (min. 20 mm), under perpendicular detachment force, in contrast under shearing force the holding force is lower. Additionally, even a small distance {between} the magnet’s surface and the plate lowers the load capacity.