SMZR 25x150 / N52 - magnetic separator with handle

Advantages as well as disadvantages of neodymium magnets NdFeB.

Apart from their notable magnetic energy, neodymium magnets have these key benefits:

• They virtually do not lose power, because even after ten years, the performance loss is only ~1% (according to literature),
• They remain magnetized despite exposure to strong external fields,
• In other words, due to the glossy gold coating, the magnet obtains an stylish appearance,
• They possess strong magnetic force measurable at the magnet’s surface,
• Thanks to their enhanced temperature resistance, they can operate (depending on the form) even at temperatures up to 230°C or more,
• The ability for precise shaping as well as adaptation to custom needs – neodymium magnets can be manufactured in multiple variants of geometries, which extends the scope of their use cases,
• Wide application in advanced technical fields – they are used in computer drives, electromechanical systems, healthcare devices as well as sophisticated instruments,
• Thanks to their concentrated strength, small magnets offer high magnetic performance, while occupying minimal space,

Disadvantages of NdFeB magnets:

• They are prone to breaking when subjected to a heavy impact. If the magnets are exposed to physical collisions, they should be placed in a protective case. The steel housing, in the form of a holder, protects the magnet from cracks while also enhances its overall robustness,
• Magnets lose field strength when exposed to temperatures exceeding 80°C. In most cases, this leads to irreversible power drop (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 wet conditions can rust. Therefore, for outdoor applications, we advise waterproof types made of plastic,
• Using a cover – such as a magnetic holder – is advised due to the challenges in manufacturing complex structures directly in the magnet,
• Safety concern from tiny pieces may arise, when consumed by mistake, which is notable in the family environments. Additionally, minuscule fragments from these devices may hinder health screening when ingested,
• Higher purchase price is an important factor to consider compared to ceramic magnets, especially in budget-sensitive applications

Maximum magnetic pulling force – what contributes to it?

The given lifting capacity of the magnet represents the maximum lifting force, determined in the best circumstances, that is:

• using a steel plate with low carbon content, acting as a magnetic circuit closure
• having a thickness of no less than 10 millimeters
• with a polished side
• with zero air gap
• under perpendicular detachment force
• at room temperature

Impact of factors on magnetic holding capacity in practice

The lifting capacity of a magnet is determined by in practice the following factors, 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 determined using a smooth steel plate of suitable thickness (min. 20 mm), under perpendicular pulling force, whereas under shearing force the lifting capacity is smaller. Additionally, even a slight gap {between} the magnet’s surface and the plate decreases the load capacity.