MP 10x4.3x4 / N38 - ring magnet

Advantages as well as disadvantages of NdFeB magnets.

In addition to their magnetic capacity, neodymium magnets provide the following advantages:

• They do not lose strength, even after nearly ten years – the decrease in power is only ~1% (based on measurements),
• They show high resistance to demagnetization induced by presence of other magnetic fields,
• A magnet with a metallic nickel surface has an effective appearance,
• The surface of neodymium magnets generates a concentrated magnetic field – this is one of their assets,
• Neodymium magnets are characterized by extremely high magnetic induction on the magnet surface and can work (depending on the form) even at a temperature of 230°C or more...
• Possibility of accurate machining and optimizing to complex requirements,
• Wide application in future technologies – they are utilized in hard drives, brushless drives, medical devices, as well as modern systems.
• Relatively small size with high pulling force – neodymium magnets offer high power in tiny dimensions, which allows their use in small systems

Cons of neodymium magnets and proposals for their use:

• They are prone to damage upon heavy impacts. To avoid cracks, it is worth securing magnets in a protective case. Such protection not only shields the magnet but also improves its resistance to damage
• When exposed to high temperature, neodymium magnets suffer a drop in force. Often, when the temperature exceeds 80°C, their strength decreases (depending on the size, as well as shape of the magnet). For those who need magnets for extreme conditions, we offer [AH] versions withstanding up to 230°C
• Magnets exposed to a humid environment can corrode. Therefore during using outdoors, we suggest using water-impermeable magnets made of rubber, plastic or other material resistant to moisture
• We suggest cover - magnetic holder, due to difficulties in creating threads inside the magnet and complex shapes.
• Possible danger related to microscopic parts of magnets pose a threat, in case of ingestion, which gains importance in the context of child health protection. Additionally, small elements of these magnets are able to complicate diagnosis medical after entering the body.
• High unit price – neodymium magnets cost more than other types of magnets (e.g. ferrite), which increases costs of application in large quantities

Breakaway strength of the magnet in ideal conditions – what it depends on?

Breakaway force was defined for the most favorable conditions, assuming:

• on a base made of mild steel, perfectly concentrating the magnetic field
• possessing a thickness of min. 10 mm to avoid saturation
• with a surface cleaned and smooth
• with direct contact (no paint)
• under vertical force vector (90-degree angle)
• at room temperature

Practical aspects of lifting capacity – factors

It is worth knowing that the application force may be lower depending on elements below, in order of importance:

• Air gap (between the magnet and the metal), since even a very small clearance (e.g. 0.5 mm) leads to a reduction in lifting capacity by up to 50% (this also applies to paint, corrosion or debris).
• Direction of force – maximum parameter is reached only during perpendicular pulling. The shear force of the magnet along the plate is usually several times lower (approx. 1/5 of the lifting capacity).
• Element thickness – to utilize 100% power, the steel must be adequately massive. Thin sheet limits the attraction force (the magnet "punches through" it).
• Metal type – different alloys reacts the same. High carbon content worsen the interaction with the magnet.
• Surface finish – ideal contact is possible only on smooth steel. Rough texture reduce the real contact area, reducing force.
• Heat – NdFeB sinters have a sensitivity to temperature. When it is hot they are weaker, and in frost they can be stronger (up to a certain limit).

* Lifting capacity testing was conducted on plates with a smooth surface of optimal thickness, under perpendicular forces, whereas under attempts to slide the magnet the load capacity is reduced by as much as 75%. In addition, even a minimal clearance {between} the magnet’s surface and the plate reduces the load capacity.