UMGZ 20x15x7 [M4] GZ / N38 - magnetic holder external thread

Advantages as well as disadvantages of neodymium magnets NdFeB.

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

• They do not lose their power around 10 years – the reduction of lifting capacity is only ~1% (according to tests),
• They show strong resistance to demagnetization from outside magnetic sources,
• By applying a shiny layer of nickel, the element gains a sleek look,
• Magnetic induction on the surface of these magnets is impressively powerful,
• They are suitable for high-temperature applications, operating effectively at 230°C+ due to advanced heat resistance and form-specific properties,
• The ability for accurate shaping as well as adaptation to individual needs – neodymium magnets can be manufactured in many forms and dimensions, which enhances their versatility in applications,
• Significant impact in advanced technical fields – they find application in hard drives, electric drives, clinical machines along with sophisticated instruments,
• Compactness – despite their small size, they deliver powerful magnetism, making them ideal for precision applications

Disadvantages of NdFeB magnets:

• They may fracture when subjected to a strong impact. If the magnets are exposed to mechanical hits, they should be placed in a metal holder. The steel housing, in the form of a holder, protects the magnet from damage and enhances its overall strength,
• High temperatures may significantly reduce the field efficiency of neodymium magnets. Typically, above 80°C, they experience permanent weakening in performance (depending on height). To prevent this, we offer heat-resistant magnets marked [AH], capable of working up to 230°C, which makes them perfect for high-temperature use,
• They rust in a moist environment, especially when used outside, we recommend using sealed magnets, such as those made of plastic,
• The use of a protective casing or external holder is recommended, since machining threads in neodymium magnets is not feasible,
• Health risk from tiny pieces may arise, if ingested accidentally, which is important in the health of young users. Additionally, small elements from these assemblies might hinder health screening once in the system,
• High unit cost – neodymium magnets are costlier than other types of magnets (e.g., ferrite), which can restrict large-scale applications

Maximum holding power of the magnet – what it depends on?

The given strength of the magnet represents the optimal strength, determined in ideal conditions, specifically:

• using a steel plate with low carbon content, serving as a magnetic circuit closure
• with a thickness of minimum 10 mm
• with a refined outer layer
• in conditions of no clearance
• in a perpendicular direction of force
• in normal thermal conditions

Lifting capacity in practice – influencing factors

Practical lifting force is determined by factors, by priority:

• 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 measured on a smooth steel plate of 20 mm thickness, when the force acted perpendicularly, in contrast under shearing force the lifting capacity is smaller. In addition, even a minimal clearance {between} the magnet’s surface and the plate decreases the holding force.