UMC 75x11/6x18 / N38 - cylindrical magnetic holder

Advantages and disadvantages of neodymium magnets NdFeB.

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

• They retain their attractive force for almost 10 years – the loss is just ~1% (in theory),
• They are extremely resistant to demagnetization caused by external magnetic sources,
• Because of the brilliant layer of nickel, the component looks aesthetically refined,
• They possess intense magnetic force measurable at the magnet’s surface,
• Neodymium magnets are known for strong magnetic induction and the ability to work at temperatures up to 230°C or higher (depending on the magnetic form),
• With the option for fine forming and personalized design, these magnets can be produced in numerous shapes and sizes, greatly improving engineering flexibility,
• Important function in advanced technical fields – they are used in hard drives, electric motors, medical equipment as well as technologically developed systems,
• Thanks to their efficiency per volume, small magnets offer high magnetic performance, in miniature format,

Disadvantages of rare earth magnets:

• They may fracture when subjected to a strong impact. If the magnets are exposed to mechanical hits, it is advisable to use in a metal holder. The steel housing, in the form of a holder, protects the magnet from cracks while also reinforces its overall resistance,
• They lose magnetic force at high temperatures. Most neodymium magnets experience permanent degradation in strength when heated above 80°C (depending on the form and height). However, we offer special variants with high temperature resistance that can operate up to 230°C or higher,
• Magnets exposed to damp air can corrode. Therefore, for outdoor applications, we suggest waterproof types made of plastic,
• Using a cover – such as a magnetic holder – is advised due to the limitations in manufacturing threads directly in the magnet,
• Safety concern due to small fragments may arise, if ingested accidentally, which is significant in the protection of children. Furthermore, tiny components from these products might complicate medical imaging when ingested,
• Due to a complex production process, their cost is considerably higher,

Highest magnetic holding force – what contributes to it?

The given pulling force of the magnet represents the maximum force, calculated in the best circumstances, specifically:

• using a steel plate with low carbon content, serving as a magnetic circuit closure
• of a thickness of at least 10 mm
• with a polished side
• with zero air gap
• under perpendicular detachment force
• in normal thermal conditions

Determinants of practical lifting force of a magnet

Practical lifting force is dependent on factors, listed from the most critical to the less significant:

• Air gap between the magnet and the plate, as 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 a smooth plate of suitable thickness, under perpendicular forces, in contrast under shearing force the holding force is lower. Additionally, even a slight gap {between} the magnet and the plate reduces the lifting capacity.