UMS 32x10.5x5.5x8 / N38 - conical magnetic holder

Advantages and disadvantages of neodymium magnets NdFeB.

Apart from their notable holding force, neodymium magnets have these key benefits:

• They have stable power, and over nearly 10 years their attraction force decreases symbolically – ~1% (in testing),
• They are very resistant to demagnetization caused by external magnetic sources,
• Thanks to the shiny finish and gold coating, they have an visually attractive appearance,
• They exhibit elevated levels of magnetic induction near the outer area of the magnet,
• They are suitable for high-temperature applications, operating effectively at 230°C+ due to advanced heat resistance and form-specific properties,
• With the option for tailored forming and precise design, these magnets can be produced in multiple shapes and sizes, greatly improving application potential,
• Important function in advanced technical fields – they serve a purpose in HDDs, electric motors, diagnostic apparatus as well as sophisticated instruments,
• Relatively small size with high magnetic force – neodymium magnets offer strong power in small dimensions, which makes them ideal in miniature devices

Disadvantages of magnetic elements:

• They may fracture when subjected to a heavy impact. If the magnets are exposed to external force, they should be placed in a protective enclosure. The steel housing, in the form of a holder, protects the magnet from damage while also reinforces its overall strength,
• They lose magnetic force at high temperatures. Most neodymium magnets experience permanent reduction 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 humidity can rust. Therefore, for outdoor applications, we recommend waterproof types made of coated materials,
• The use of a protective casing or external holder is recommended, since machining internal cuts in neodymium magnets is restricted,
• Possible threat due to small fragments may arise, in case of ingestion, which is important in the protection of children. It should also be noted that miniature parts from these products may complicate medical imaging once in the system,
• High unit cost – neodymium magnets are costlier than other types of magnets (e.g., ferrite), which increases the cost of large-scale applications

Best holding force of the magnet in ideal parameters – what contributes to it?

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

• using a steel plate with low carbon content, serving as a magnetic circuit closure
• having a thickness of no less than 10 millimeters
• with a refined outer layer
• with zero air gap
• with vertical force applied
• in normal thermal conditions

Determinants of lifting force in real conditions

The lifting capacity of a magnet depends on in practice the following factors, according to their 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.

* Holding force was checked on the plate surface of 20 mm thickness, when a perpendicular force was applied, however under parallel forces the lifting capacity is smaller. Moreover, even a slight gap {between} the magnet’s surface and the plate decreases the holding force.