MP 25x5x27 / N38 - ring magnet

Advantages and disadvantages of neodymium magnets NdFeB.

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

• They retain their full power for nearly 10 years – the loss is just ~1% (based on simulations),
• They remain magnetized despite exposure to magnetic noise,
• By applying a shiny layer of nickel, the element gains a clean look,
• They exhibit superior levels of magnetic induction near the outer area of the magnet,
• These magnets tolerate elevated temperatures, often exceeding 230°C, when properly designed (in relation to profile),
• The ability for custom shaping or customization to specific needs – neodymium magnets can be manufactured in multiple variants of geometries, which amplifies their functionality across industries,
• Important function in advanced technical fields – they are used in HDDs, electric drives, healthcare devices along with high-tech tools,
• Compactness – despite their small size, they generate strong force, making them ideal for precision applications

Disadvantages of rare earth magnets:

• They may fracture 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 fracture and additionally enhances its overall durability,
• They lose magnetic force at high temperatures. Most neodymium magnets experience permanent degradation in strength when heated above 80°C (depending on the dimensions 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 wise to use sealed magnets made of plastic for outdoor use,
• Limited ability to create complex details in the magnet – the use of a magnetic holder is recommended,
• Health risk due to small fragments may arise, especially if swallowed, which is crucial in the protection of children. Additionally, miniature parts from these assemblies might interfere with diagnostics once in the system,
• Higher purchase price is an important factor to consider compared to ceramic magnets, especially in budget-sensitive applications

Magnetic strength at its maximum – what affects it?

The given holding capacity of the magnet corresponds to the highest holding force, calculated under optimal conditions, specifically:

• using a steel plate with low carbon content, serving as a magnetic circuit closure
• with a thickness of minimum 10 mm
• with a refined outer layer
• in conditions of no clearance
• with vertical force applied
• at room temperature

Magnet lifting force in use – key factors

In practice, the holding capacity of a magnet is conditioned by these factors, in descending order of importance:

• 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 testing was carried out on plates with a smooth surface of suitable thickness, under a perpendicular pulling force, in contrast under attempts to slide the magnet the load capacity is reduced by as much as 5 times. Additionally, even a slight gap {between} the magnet and the plate reduces the load capacity.