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

Advantages as well as disadvantages of neodymium magnets NdFeB.

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

• Their magnetic field is durable, and after around 10 years, it drops only by ~1% (theoretically),
• Their ability to resist magnetic interference from external fields is impressive,
• Because of the lustrous layer of nickel, the component looks aesthetically refined,
• The outer field strength of the magnet shows advanced magnetic properties,
• Neodymium magnets are known for exceptionally strong magnetic induction and the ability to work at temperatures up to 230°C or higher (depending on the geometry),
• With the option for tailored forming and personalized design, these magnets can be produced in numerous shapes and sizes, greatly improving engineering flexibility,
• Key role in modern technologies – they are utilized in hard drives, electric motors, clinical machines or even high-tech tools,
• Compactness – despite their small size, they generate strong force, making them ideal for precision applications

Disadvantages of neodymium magnets:

• They are prone to breaking when subjected to a powerful impact. If the magnets are exposed to mechanical hits, they should be placed in a protective enclosure. The steel housing, in the form of a holder, protects the magnet from cracks , and at the same time reinforces its overall strength,
• Magnets lose field strength when exposed to temperatures exceeding 80°C. In most cases, this leads to irreversible magnetic decay (influenced by the magnet’s dimensions). To address this, we provide [AH] models with superior thermal resistance, able to operate even at 230°C or more,
• They rust in a moist environment, especially when used outside, we recommend using waterproof magnets, such as those made of non-metallic materials,
• Using a cover – such as a magnetic holder – is advised due to the challenges in manufacturing threads directly in the magnet,
• Health risk related to magnet particles may arise, in case of ingestion, which is significant in the context of child safety. Moreover, miniature parts from these magnets might hinder health screening after being swallowed,
• Higher purchase price is one of the drawbacks compared to ceramic magnets, especially in budget-sensitive applications

Maximum lifting force for a neodymium magnet – what it depends on?

The given strength of the magnet means the optimal strength, assessed in ideal conditions, that is:

• using a steel plate with low carbon content, acting as a magnetic circuit closure
• of a thickness of at least 10 mm
• with a polished side
• in conditions of no clearance
• with vertical force applied
• in normal thermal conditions

Impact of factors on magnetic holding capacity in practice

The lifting capacity of a magnet is determined by 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) 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 measured using a smooth steel plate of suitable thickness (min. 20 mm), under vertically applied force, in contrast under shearing force the holding force is lower. Moreover, even a slight gap {between} the magnet’s surface and the plate decreases the lifting capacity.