UMC 25x6/4x8 / N38 - cylindrical magnetic holder

Advantages as well as disadvantages of neodymium magnets NdFeB.

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

• Their strength remains stable, and after around ten years, it drops only by ~1% (according to research),
• They remain magnetized despite exposure to magnetic surroundings,
• The use of a decorative gold surface provides a smooth finish,
• They exhibit extremely high levels of magnetic induction near the outer area of the magnet,
• These magnets tolerate high temperatures, often exceeding 230°C, when properly designed (in relation to form),
• With the option for fine forming and targeted design, these magnets can be produced in multiple shapes and sizes, greatly improving application potential,
• Key role in modern technologies – they are used in computer drives, rotating machines, clinical machines and other advanced devices,
• Thanks to their power density, small magnets offer high magnetic performance, in miniature format,

Disadvantages of rare earth magnets:

• They can break when subjected to a strong impact. If the magnets are exposed to shocks, they should be placed in a metal holder. The steel housing, in the form of a holder, protects the magnet from cracks and additionally enhances its overall robustness,
• Magnets lose power when exposed to temperatures exceeding 80°C. In most cases, this leads to irreversible field weakening (influenced by the magnet’s form). To address this, we provide [AH] models with superior thermal resistance, able to operate even at 230°C or more,
• Magnets exposed to damp air can rust. Therefore, for outdoor applications, we recommend waterproof types made of coated materials,
• Using a cover – such as a magnetic holder – is advised due to the restrictions in manufacturing threads directly in the magnet,
• Health risk from tiny pieces may arise, especially if swallowed, which is significant in the family environments. Moreover, tiny components from these products might hinder health screening when ingested,
• Higher purchase price is one of the drawbacks compared to ceramic magnets, especially in budget-sensitive applications

Maximum lifting capacity of the magnet – what affects it?

The given holding capacity of the magnet corresponds to the highest holding force, measured in the best circumstances, namely:

• with mild steel, used as a magnetic flux conductor
• having a thickness of no less than 10 millimeters
• with a refined outer layer
• in conditions of no clearance
• with vertical force applied
• in normal thermal conditions

Lifting capacity in real conditions – factors

Practical lifting force is dependent on factors, by priority:

• Air gap between the magnet and the plate, as even a very small distance (e.g. 0.5 mm) causes 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 assessed by applying a polished steel plate of optimal thickness (min. 20 mm), under vertically applied force, however under parallel forces the load capacity is reduced by as much as 5 times. Moreover, even a small distance {between} the magnet and the plate decreases the holding force.