UMH 20x7x35 [M4] / N38 - magnetic holder with hook

Advantages and disadvantages of neodymium magnets NdFeB.

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

• They do not lose their power nearly 10 years – the reduction of power is only ~1% (based on measurements),
• Their ability to resist magnetic interference from external fields is among the best,
• The use of a decorative silver surface provides a smooth finish,
• They exhibit elevated levels of magnetic induction near the outer area of the magnet,
• Neodymium magnets are known for strong magnetic induction and the ability to work at temperatures up to 230°C or higher (depending on the shape),
• The ability for precise shaping and customization to specific needs – neodymium magnets can be manufactured in many forms and dimensions, which amplifies their functionality across industries,
• Important function in cutting-edge sectors – they find application in HDDs, electromechanical systems, diagnostic apparatus along with sophisticated instruments,
• Relatively small size with high magnetic force – neodymium magnets offer intense magnetic field in small dimensions, which makes them ideal in compact constructions

Disadvantages of NdFeB magnets:

• They may fracture when subjected to a heavy impact. If the magnets are exposed to mechanical hits, they should be placed in a steel housing. The steel housing, in the form of a holder, protects the magnet from cracks while also enhances its overall robustness,
• High temperatures may significantly reduce the strength of neodymium magnets. Typically, above 80°C, they experience permanent loss in performance (depending on form). 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 humid environment, especially when used outside, we recommend using encapsulated magnets, such as those made of non-metallic materials,
• The use of a protective casing or external holder is recommended, since machining threads in neodymium magnets is risky,
• Possible threat related to magnet particles may arise, when consumed by mistake, which is crucial in the context of child safety. Moreover, minuscule fragments from these assemblies might interfere with diagnostics after being swallowed,
• Higher purchase price is an important factor to consider compared to ceramic magnets, especially in budget-sensitive applications

Magnetic strength at its maximum – what it depends on?

The given pulling force of the magnet represents the maximum force, measured under optimal 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 smooth surface
• in conditions of no clearance
• with vertical force applied
• under standard ambient temperature

Practical aspects of lifting capacity – factors

Practical lifting force is dependent on elements, by priority:

• Air gap between the magnet and the plate, because 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 was determined using a steel plate with a smooth surface of optimal thickness (min. 20 mm), under perpendicular detachment force, whereas under attempts to slide the magnet the load capacity is reduced by as much as fivefold. Moreover, even a minimal clearance {between} the magnet and the plate lowers the lifting capacity.