MP 25x13x4 / N38 - ring magnet

Advantages as well as disadvantages of neodymium magnets NdFeB.

In addition to their remarkable strength, neodymium magnets offer the following advantages:

• They retain their attractive force for nearly ten years – the loss is just ~1% (according to analyses),
• They remain magnetized despite exposure to magnetic surroundings,
• By applying a shiny layer of gold, the element gains a modern look,
• Magnetic induction on the surface of these magnets is impressively powerful,
• These magnets tolerate elevated temperatures, often exceeding 230°C, when properly designed (in relation to build),
• With the option for customized forming and precise design, these magnets can be produced in various shapes and sizes, greatly improving engineering flexibility,
• Wide application in new technology industries – they are utilized in HDDs, electric drives, diagnostic apparatus as well as high-tech tools,
• Relatively small size with high magnetic force – neodymium magnets offer impressive pulling strength in small dimensions, which makes them useful in compact constructions

Disadvantages of magnetic elements:

• They can break when subjected to a heavy impact. If the magnets are exposed to external force, it is suggested to place them in a protective case. The steel housing, in the form of a holder, protects the magnet from fracture and additionally reinforces its overall robustness,
• They lose strength at extreme temperatures. Most neodymium magnets experience permanent decline in strength when heated above 80°C (depending on the shape 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 protective material for outdoor use,
• Limited ability to create complex details in the magnet – the use of a magnetic holder is recommended,
• Possible threat linked to microscopic shards may arise, when consumed by mistake, which is important in the context of child safety. It should also be noted that small elements from these magnets may disrupt scanning when ingested,
• Higher purchase price is an important factor to consider compared to ceramic magnets, especially in budget-sensitive applications

Breakaway strength of the magnet in ideal conditions – what affects it?

The given lifting capacity of the magnet represents the maximum lifting force, calculated in a perfect environment, that is:

• with the use of low-carbon steel plate acting as a magnetic yoke
• having a thickness of no less than 10 millimeters
• with a polished side
• with zero air gap
• under perpendicular detachment force
• at room temperature

Lifting capacity in real conditions – factors

The lifting capacity of a magnet is determined by in practice key elements, according to their 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.

* Holding force was tested on the plate surface of 20 mm thickness, when a perpendicular force was applied, whereas under attempts to slide the magnet the holding force is lower. Additionally, even a slight gap {between} the magnet’s surface and the plate decreases the lifting capacity.