MW 45x35 / N38 - cylindrical magnet

Advantages as well as disadvantages of neodymium magnets NdFeB.

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

• They retain their full power for nearly 10 years – the drop is just ~1% (according to analyses),
• They protect against demagnetization induced by external magnetic influence remarkably well,
• In other words, due to the metallic gold coating, the magnet obtains an aesthetic appearance,
• They have exceptional magnetic induction on the surface of the magnet,
• With the right combination of compounds, they reach excellent thermal stability, enabling operation at or above 230°C (depending on the form),
• With the option for fine forming and precise design, these magnets can be produced in numerous shapes and sizes, greatly improving application potential,
• Important function in advanced technical fields – they serve a purpose in hard drives, electric motors, diagnostic apparatus as well as technologically developed systems,
• Relatively small size with high magnetic force – neodymium magnets offer intense magnetic field in tiny dimensions, which allows for use in miniature devices

Disadvantages of NdFeB magnets:

• They can break when subjected to a heavy impact. If the magnets are exposed to physical collisions, it is advisable to use in a protective case. The steel housing, in the form of a holder, protects the magnet from cracks , and at the same time enhances its overall strength,
• Magnets lose pulling force when exposed to temperatures exceeding 80°C. In most cases, this leads to irreversible field weakening (influenced by the magnet’s structure). To address this, we provide [AH] models with superior thermal resistance, able to operate even at 230°C or more,
• Due to corrosion risk in humid conditions, it is wise to use sealed magnets made of plastic for outdoor use,
• Using a cover – such as a magnetic holder – is advised due to the difficulty in manufacturing fine shapes directly in the magnet,
• Health risk from tiny pieces may arise, if ingested accidentally, which is crucial in the context of child safety. It should also be noted that tiny components from these magnets can hinder health screening if inside the body,
• Higher purchase price is an important factor to consider compared to ceramic magnets, especially in budget-sensitive applications

Maximum lifting capacity of the magnet – what it depends on?

The given strength of the magnet corresponds to the optimal strength, assessed under optimal conditions, namely:

• with mild steel, serving as a magnetic flux conductor
• of a thickness of at least 10 mm
• with a refined outer layer
• with zero air gap
• under perpendicular detachment force
• in normal thermal conditions

Lifting capacity in real conditions – factors

In practice, the holding capacity of a magnet is affected by these factors, in descending order of importance:

• 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.

* Lifting capacity was measured using a smooth steel plate of suitable thickness (min. 20 mm), under perpendicular pulling force, whereas under shearing force the lifting capacity is smaller. Moreover, even a slight gap {between} the magnet’s surface and the plate decreases the lifting capacity.