MP 25x13x4 / N38 - ring magnet

Advantages and disadvantages of rare earth magnets.

Besides their high retention, neodymium magnets are valued for these benefits:

• They have unchanged lifting capacity, and over around ten years their performance decreases symbolically – ~1% (in testing),
• Neodymium magnets are extremely resistant to demagnetization caused by external interference,
• The use of an metallic finish of noble metals (nickel, gold, silver) causes the element to be more visually attractive,
• Magnetic induction on the working layer of the magnet remains exceptional,
• Through (adequate) combination of ingredients, they can achieve high thermal resistance, enabling operation at temperatures approaching 230°C and above...
• Possibility of exact forming and modifying to complex conditions,
• Universal use in modern industrial fields – they are used in magnetic memories, electric drive systems, precision medical tools, as well as technologically advanced constructions.
• Thanks to concentrated force, small magnets offer high operating force, with minimal size,

Disadvantages of NdFeB magnets:

• At strong impacts they can break, therefore we recommend placing them in strong housings. A metal housing provides additional protection against damage and increases the magnet's durability.
• We warn that neodymium magnets can reduce their strength at high temperatures. To prevent this, we recommend our specialized [AH] magnets, which work effectively even at 230°C.
• When exposed to humidity, magnets start to rust. To use them in conditions outside, it is recommended to use protective magnets, such as those in rubber or plastics, which prevent oxidation and corrosion.
• We suggest casing - magnetic mechanism, due to difficulties in creating nuts inside the magnet and complex shapes.
• Possible danger resulting from small fragments of magnets pose a threat, in case of ingestion, which becomes key in the aspect of protecting the youngest. It is also worth noting that small components of these devices can complicate diagnosis medical when they are in the body.
• High unit price – neodymium magnets have a higher price than other types of magnets (e.g. ferrite), which can limit application in large quantities

Detachment force of the magnet in optimal conditions – what affects it?

The specified lifting capacity concerns the peak performance, obtained under optimal environment, specifically:

• with the use of a yoke made of low-carbon steel, ensuring maximum field concentration
• possessing a massiveness of minimum 10 mm to avoid saturation
• characterized by even structure
• under conditions of ideal adhesion (surface-to-surface)
• for force acting at a right angle (pull-off, not shear)
• at ambient temperature approx. 20 degrees Celsius

Practical lifting capacity: influencing factors

In real-world applications, the actual holding force results from several key aspects, presented from the most important:

• Distance – the presence of foreign body (rust, dirt, gap) interrupts the magnetic circuit, which lowers power steeply (even by 50% at 0.5 mm).
• Load vector – highest force is available only during pulling at a 90° angle. The shear force of the magnet along the surface is standardly several times lower (approx. 1/5 of the lifting capacity).
• Wall thickness – thin material does not allow full use of the magnet. Part of the magnetic field passes through the material instead of generating force.
• Steel type – low-carbon steel gives the best results. Alloy admixtures lower magnetic properties and holding force.
• Surface structure – the smoother and more polished the plate, the better the adhesion and higher the lifting capacity. Unevenness creates an air distance.
• Thermal environment – heating the magnet results in weakening of force. It is worth remembering the maximum operating temperature for a given model.

* Lifting capacity testing was carried out on a smooth plate of suitable thickness, under perpendicular forces, however under parallel forces the load capacity is reduced by as much as 75%. In addition, even a small distance {between} the magnet’s surface and the plate lowers the holding force.