MW 70x60 / N38 - cylindrical magnet

Advantages as well as disadvantages of neodymium magnets NdFeB.

Besides their stability, neodymium magnets are valued for these benefits:

• They have stable power, and over nearly 10 years their attraction force decreases symbolically – ~1% (in testing),
• They show exceptional resistance to demagnetization from external magnetic fields,
• In other words, due to the metallic gold coating, the magnet obtains an stylish appearance,
• Magnetic induction on the surface of these magnets is impressively powerful,
• Thanks to their enhanced temperature resistance, they can operate (depending on the geometry) even at temperatures up to 230°C or more,
• The ability for precise shaping as well as customization to specific needs – neodymium magnets can be manufactured in a wide range of shapes and sizes, which enhances their versatility in applications,
• Significant impact in advanced technical fields – they serve a purpose in computer drives, electric motors, diagnostic apparatus as well as sophisticated instruments,
• Relatively small size with high magnetic force – neodymium magnets offer impressive pulling strength in tiny dimensions, which allows for use in compact constructions

Disadvantages of neodymium magnets:

• They are fragile when subjected to a powerful impact. If the magnets are exposed to physical collisions, it is advisable to use in a protective enclosure. The steel housing, in the form of a holder, protects the magnet from fracture and increases its overall resistance,
• They lose power at elevated 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,
• They rust in a moist environment. If exposed to rain, we recommend using sealed magnets, such as those made of plastic,
• Using a cover – such as a magnetic holder – is advised due to the difficulty in manufacturing threads directly in the magnet,
• Health risk due to small fragments may arise, in case of ingestion, which is crucial in the protection of children. It should also be noted that miniature parts from these products may disrupt scanning after being swallowed,
• Higher purchase price is one of the drawbacks compared to ceramic magnets, especially in budget-sensitive applications

Highest magnetic holding force – what it depends on?

The given holding capacity of the magnet represents the highest holding force, assessed under optimal conditions, that is:

• with mild steel, serving as a magnetic flux conductor
• of a thickness of at least 10 mm
• with a polished side
• with zero air gap
• under perpendicular detachment force
• in normal thermal conditions

Determinants of lifting force in real conditions

Practical lifting force is dependent on elements, listed from the most critical to the less significant:

• Air gap between the magnet and the plate, since 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.

* Holding force was tested on a smooth steel plate of 20 mm thickness, when the force acted perpendicularly, however under attempts to slide the magnet the lifting capacity is smaller. Moreover, even a slight gap {between} the magnet’s surface and the plate lowers the load capacity.