MW 8x8 / N38 - cylindrical magnet

Advantages as well as disadvantages of neodymium magnets NdFeB.

In addition to their exceptional pulling force, neodymium magnets offer the following advantages:

• They have constant strength, and over more than 10 years their attraction force decreases symbolically – ~1% (according to theory),
• They show exceptional resistance to demagnetization from external field exposure,
• By applying a shiny layer of gold, the element gains a modern look,
• They possess strong magnetic force measurable at the magnet’s surface,
• Neodymium magnets are known for 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 multiple shapes and sizes, greatly improving engineering flexibility,
• Important function in new technology industries – they serve a purpose in data storage devices, electromechanical systems, clinical machines along with sophisticated instruments,
• Thanks to their concentrated strength, small magnets offer high magnetic performance, while occupying minimal space,

Disadvantages of rare earth magnets:

• They are prone to breaking when subjected to a heavy impact. If the magnets are exposed to external force, we recommend in a steel housing. The steel housing, in the form of a holder, protects the magnet from cracks while also reinforces its overall strength,
• They lose magnetic force at high temperatures. Most neodymium magnets experience permanent loss in strength when heated above 80°C (depending on the geometry and height). However, we offer special variants with high temperature resistance that can operate up to 230°C or higher,
• Due to corrosion risk in humid conditions, it is advisable to use sealed magnets made of plastic for outdoor use,
• Using a cover – such as a magnetic holder – is advised due to the limitations in manufacturing complex structures directly in the magnet,
• Potential hazard linked to microscopic shards may arise, especially if swallowed, which is crucial in the protection of children. Additionally, miniature parts from these assemblies have the potential to hinder health screening after being swallowed,
• Due to expensive raw materials, their cost is above average,

Maximum magnetic pulling force – what it depends on?

The given pulling force of the magnet corresponds to the maximum force, determined in ideal conditions, namely:

• with mild steel, used as a magnetic flux conductor
• of a thickness of at least 10 mm
• with a refined outer layer
• in conditions of no clearance
• with vertical force applied
• in normal thermal conditions

Key elements affecting lifting force

Practical lifting force is determined by factors, listed from the most critical to the less significant:

• 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 with the use of a smooth steel plate of optimal thickness (min. 20 mm), under vertically applied force, however under attempts to slide the magnet the lifting capacity is smaller. In addition, even a minimal clearance {between} the magnet’s surface and the plate lowers the load capacity.