UMH 20x7x35 [M4] / N38 - magnetic holder with hook

Advantages and disadvantages of neodymium magnets NdFeB.

In addition to their tremendous field intensity, neodymium magnets offer the following advantages:

• They retain their attractive force for nearly 10 years – the loss is just ~1% (based on simulations),
• They remain magnetized despite exposure to strong external fields,
• By applying a shiny layer of nickel, the element gains a modern look,
• They have very high magnetic induction on the surface of the magnet,
• With the right combination of magnetic alloys, they reach significant thermal stability, enabling operation at or above 230°C (depending on the design),
• Thanks to the freedom in shaping and the capability to adapt to specific requirements, neodymium magnets can be created in different geometries, which broadens their functional possibilities,
• Significant impact in cutting-edge sectors – they find application in computer drives, electric drives, diagnostic apparatus and sophisticated instruments,
• Relatively small size with high magnetic force – neodymium magnets offer impressive pulling strength in small dimensions, which makes them useful in compact constructions

Disadvantages of rare earth magnets:

• They can break when subjected to a sudden impact. If the magnets are exposed to shocks, it is suggested to place them in a steel housing. The steel housing, in the form of a holder, protects the magnet from damage , and at the same time strengthens its overall strength,
• Magnets lose power when exposed to temperatures exceeding 80°C. In most cases, this leads to irreversible performance loss (influenced by the magnet’s structure). 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 oxidize. Therefore, for outdoor applications, it's best to use waterproof types made of plastic,
• Limited ability to create internal holes in the magnet – the use of a mechanical support is recommended,
• Health risk related to magnet particles may arise, when consumed by mistake, which is significant in the health of young users. Furthermore, minuscule fragments from these devices have the potential to hinder health screening once in the system,
• Due to expensive raw materials, their cost is considerably higher,

Optimal lifting capacity of a neodymium magnet – what affects it?

The given pulling force of the magnet corresponds to the maximum force, determined under optimal conditions, that is:

• with the use of low-carbon steel plate serving as a magnetic yoke
• having a thickness of no less than 10 millimeters
• with a refined outer layer
• in conditions of no clearance
• under perpendicular detachment force
• in normal thermal conditions

Magnet lifting force in use – key factors

The lifting capacity of a magnet depends on in practice key elements, from primary to secondary:

• Air gap between the magnet and the plate, because 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 measured by applying a steel plate with a smooth surface of suitable thickness (min. 20 mm), under vertically applied force, whereas under parallel forces the load capacity is reduced by as much as 5 times. In addition, even a slight gap {between} the magnet’s surface and the plate decreases the holding force.