CM PML-3 / N45 - magnetic gripper

Strengths as well as weaknesses of NdFeB magnets.

Apart from their strong holding force, neodymium magnets have these key benefits:

• They have stable power, and over nearly ten years their attraction force decreases symbolically – ~1% (according to theory),
• Neodymium magnets are highly resistant to demagnetization caused by external magnetic fields,
• A magnet with a shiny nickel surface has better aesthetics,
• Magnetic induction on the surface of the magnet remains extremely intense,
• Due to their durability and thermal resistance, neodymium magnets can operate (depending on the form) even at high temperatures reaching 230°C or more...
• Possibility of exact machining and optimizing to atypical applications,
• Huge importance in modern technologies – they are used in HDD drives, motor assemblies, diagnostic systems, also other advanced devices.
• Relatively small size with high pulling force – neodymium magnets offer strong magnetic field in compact dimensions, which allows their use in compact constructions

Disadvantages of neodymium magnets:

• At strong impacts they can crack, therefore we recommend placing them in strong housings. A metal housing provides additional protection against damage, as well as increases the magnet's durability.
• When exposed to high temperature, neodymium magnets experience a drop in power. Often, when the temperature exceeds 80°C, their power 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
• They rust in a humid environment. For use outdoors we recommend using waterproof magnets e.g. in rubber, plastic
• We recommend cover - magnetic mechanism, due to difficulties in realizing nuts inside the magnet and complex forms.
• Health risk resulting from small fragments of magnets can be dangerous, in case of ingestion, which gains importance in the context of child health protection. It is also worth noting that tiny parts of these products can disrupt the diagnostic process medical in case of swallowing.
• High unit price – neodymium magnets cost more than other types of magnets (e.g. ferrite), which can limit application in large quantities

Maximum holding power of the magnet – what affects it?

The load parameter shown refers to the limit force, obtained under optimal environment, namely:

• with the application of a sheet made of low-carbon steel, guaranteeing maximum field concentration
• possessing a thickness of at least 10 mm to ensure full flux closure
• characterized by lack of roughness
• under conditions of ideal adhesion (surface-to-surface)
• during detachment in a direction perpendicular to the plane
• in neutral thermal conditions

Impact of factors on magnetic holding capacity in practice

It is worth knowing that the magnet holding may be lower influenced by elements below, in order of importance:

• Distance (betwixt the magnet and the plate), as even a microscopic distance (e.g. 0.5 mm) can cause a decrease in force by up to 50% (this also applies to varnish, rust or dirt).
• Force direction – catalog parameter refers to detachment vertically. When slipping, the magnet exhibits significantly lower power (typically approx. 20-30% of nominal force).
• Steel thickness – insufficiently thick plate does not accept the full field, causing part of the flux to be lost into the air.
• Chemical composition of the base – mild steel attracts best. Higher carbon content lower magnetic properties and holding force.
• Surface finish – full contact is obtained only on polished steel. Rough texture reduce the real contact area, weakening the magnet.
• Thermal conditions – NdFeB sinters have a negative temperature coefficient. When it is hot they are weaker, and in frost they can be stronger (up to a certain limit).

* Holding force was measured on a smooth steel plate of 20 mm thickness, when the force acted perpendicularly, in contrast under parallel forces the lifting capacity is smaller. Moreover, even a slight gap {between} the magnet’s surface and the plate decreases the load capacity.