MP 60x20x5 / N38 - ring magnet

Advantages and disadvantages of neodymium magnets NdFeB.

In addition to their magnetic efficiency, neodymium magnets provide the following advantages:

• They retain their attractive force for almost ten years – the loss is just ~1% (according to analyses),
• They remain magnetized despite exposure to strong external fields,
• In other words, due to the glossy silver coating, the magnet obtains an aesthetic appearance,
• Magnetic induction on the surface of these magnets is impressively powerful,
• With the right combination of magnetic alloys, they reach increased thermal stability, enabling operation at or above 230°C (depending on the design),
• The ability for custom shaping and customization to specific needs – neodymium magnets can be manufactured in multiple variants of geometries, which enhances their versatility in applications,
• Important function in new technology industries – they are used in data storage devices, electromechanical systems, clinical machines or even high-tech tools,
• Thanks to their concentrated strength, small magnets offer high magnetic performance, with minimal size,

Disadvantages of rare earth magnets:

• They may fracture when subjected to a powerful impact. If the magnets are exposed to shocks, we recommend in a protective enclosure. The steel housing, in the form of a holder, protects the magnet from cracks while also enhances its overall strength,
• They lose field intensity at elevated temperatures. Most neodymium magnets experience permanent decline 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 recommended to use sealed magnets made of synthetic coating for outdoor use,
• The use of a protective casing or external holder is recommended, since machining threads in neodymium magnets is risky,
• Possible threat from tiny pieces may arise, especially if swallowed, which is notable in the health of young users. It should also be noted that minuscule fragments from these devices might hinder health screening when ingested,
• Higher purchase price is one of the drawbacks compared to ceramic magnets, especially in budget-sensitive applications

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

The given holding capacity of the magnet corresponds to the highest holding force, assessed in ideal conditions, that is:

• with the use of low-carbon steel plate acting as a magnetic yoke
• with a thickness of minimum 10 mm
• with a refined outer layer
• in conditions of no clearance
• under perpendicular detachment force
• in normal thermal conditions

Practical lifting capacity: influencing factors

In practice, the holding capacity of a magnet is affected by the following aspects, in descending order of importance:

• Air gap between the magnet and the plate, since even a very small distance (e.g. 0.5 mm) can cause 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 conducted on plates with a smooth surface of suitable thickness, under a perpendicular pulling force, however under parallel forces the holding force is lower. In addition, even a small distance {between} the magnet’s surface and the plate decreases the load capacity.