MP 10x7/3.5x3 / N38 - ring magnet

Advantages as well as disadvantages of neodymium magnets NdFeB.

Apart from their superior power, neodymium magnets have these key benefits:

• They virtually do not lose strength, because even after 10 years, the decline in efficiency is only ~1% (in laboratory conditions),
• They show exceptional resistance to demagnetization from outside magnetic sources,
• The use of a decorative gold surface provides a eye-catching finish,
• They exhibit elevated levels of magnetic induction near the outer area of the magnet,
• These magnets tolerate elevated temperatures, often exceeding 230°C, when properly designed (in relation to form),
• With the option for tailored forming and personalized design, these magnets can be produced in various shapes and sizes, greatly improving engineering flexibility,
• Significant impact in cutting-edge sectors – they find application in computer drives, electric motors, medical equipment or even technologically developed systems,
• Compactness – despite their small size, they deliver powerful magnetism, making them ideal for precision applications

Disadvantages of rare earth magnets:

• They can break when subjected to a powerful impact. If the magnets are exposed to external force, we recommend in a protective enclosure. The steel housing, in the form of a holder, protects the magnet from cracks , and at the same time enhances its overall robustness,
• They lose field intensity at elevated temperatures. Most neodymium magnets experience permanent decline in strength when heated above 80°C (depending on the geometry 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 non-metallic materials,
• The use of a protective casing or external holder is recommended, since machining fine details in neodymium magnets is risky,
• Potential hazard from tiny pieces may arise, in case of ingestion, which is important in the family environments. It should also be noted that miniature parts from these magnets might hinder health screening when ingested,
• High unit cost – neodymium magnets are more expensive than other types of magnets (e.g., ferrite), which can restrict large-scale applications

Breakaway strength of the magnet in ideal conditions – what contributes to it?

The given strength of the magnet corresponds to the optimal strength, measured in ideal conditions, that is:

• 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
• under standard ambient temperature

Determinants of practical lifting force of a magnet

The lifting capacity of a magnet depends on in practice key elements, ordered from most important to least significant:

• Air gap between the magnet and the plate, since 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 was measured using a polished steel plate of suitable thickness (min. 20 mm), under perpendicular pulling force, in contrast under attempts to slide the magnet the holding force is lower. In addition, even a small distance {between} the magnet and the plate decreases the lifting capacity.