UMC 42x7/4x9 / N38 - cylindrical magnetic holder

Advantages as well as disadvantages of neodymium magnets NdFeB.

Besides their magnetic performance, neodymium magnets are valued for these benefits:

• They retain their magnetic properties for around 10 years – the loss is just ~1% (in theory),
• They protect against demagnetization induced by surrounding magnetic fields effectively,
• In other words, due to the glossy nickel coating, the magnet obtains an aesthetic appearance,
• They exhibit elevated levels of magnetic induction near the outer area of the magnet,
• With the right combination of compounds, they reach increased thermal stability, enabling operation at or above 230°C (depending on the form),
• The ability for precise shaping or customization to specific needs – neodymium magnets can be manufactured in many forms and dimensions, which extends the scope of their use cases,
• Important function in cutting-edge sectors – they find application in computer drives, electric motors, medical equipment or even other advanced devices,
• 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 heavy impact. If the magnets are exposed to mechanical hits, it is advisable to use in a steel housing. The steel housing, in the form of a holder, protects the magnet from breakage and additionally reinforces its overall resistance,
• They lose power at elevated temperatures. Most neodymium magnets experience permanent degradation 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,
• They rust in a wet environment, especially when used outside, we recommend using encapsulated magnets, such as those made of polymer,
• The use of a protective casing or external holder is recommended, since machining threads in neodymium magnets is risky,
• Safety concern from tiny pieces may arise, when consumed by mistake, which is significant in the context of child safety. Furthermore, miniature parts from these devices might interfere with diagnostics when ingested,
• Higher purchase price is one of the drawbacks compared to ceramic magnets, especially in budget-sensitive applications

Maximum magnetic pulling force – what affects it?

The given holding capacity of the magnet means the highest holding force, measured in ideal conditions, specifically:

• with the use of low-carbon steel plate serving as a magnetic yoke
• of a thickness of at least 10 mm
• with a refined outer layer
• in conditions of no clearance
• under perpendicular detachment force
• under standard ambient temperature

Key elements affecting lifting force

The lifting capacity of a magnet depends on in practice key elements, from primary to secondary:

• 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 carried out on a smooth plate of optimal thickness, under perpendicular forces, in contrast under parallel forces the holding force is lower. Additionally, even a minimal clearance {between} the magnet and the plate reduces the holding force.