CM PML-3 / N45 - magnetic gripper

Strengths as well as weaknesses of neodymium magnets.

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

• They retain magnetic properties for nearly 10 years – the drop is just ~1% (according to analyses),
• Magnets effectively defend themselves against loss of magnetization caused by foreign field sources,
• A magnet with a smooth gold surface is more attractive,
• Magnetic induction on the top side of the magnet remains impressive,
• Neodymium magnets are characterized by very high magnetic induction on the magnet surface and can function (depending on the form) even at a temperature of 230°C or more...
• Possibility of exact machining and adjusting to concrete applications,
• Fundamental importance in future technologies – they are commonly used in HDD drives, electromotive mechanisms, medical devices, and technologically advanced constructions.
• Thanks to efficiency per cm³, small magnets offer high operating force, occupying minimum space,

Cons of neodymium magnets and proposals for their use:

• At very 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 strength. Often, when the temperature exceeds 80°C, their strength decreases (depending on the size and 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 when using outdoors, we recommend using water-impermeable magnets made of rubber, plastic or other material protecting against moisture
• Limited possibility of producing threads in the magnet and complicated shapes - preferred is casing - magnetic holder.
• Health risk resulting from small fragments of magnets pose a threat, if swallowed, which is particularly important in the context of child health protection. It is also worth noting that small elements of these devices can be problematic in diagnostics medical in case of swallowing.
• Higher cost of purchase is a significant factor to consider compared to ceramic magnets, especially in budget applications

Maximum lifting capacity of the magnet – what contributes to it?

The declared magnet strength refers to the peak performance, measured under ideal test conditions, meaning:

• with the use of a sheet made of low-carbon steel, guaranteeing maximum field concentration
• possessing a thickness of min. 10 mm to avoid saturation
• with an polished touching surface
• without the slightest insulating layer between the magnet and steel
• for force applied at a right angle (pull-off, not shear)
• at temperature approx. 20 degrees Celsius

Key elements affecting lifting force

During everyday use, the real power depends on a number of factors, presented from most significant:

• Space between magnet and steel – even a fraction of a millimeter of distance (caused e.g. by varnish or unevenness) drastically reduces the magnet efficiency, often by half at just 0.5 mm.
• Pull-off angle – note that the magnet has greatest strength perpendicularly. Under shear forces, the holding force drops drastically, often to levels of 20-30% of the nominal value.
• Substrate thickness – for full efficiency, the steel must be adequately massive. Thin sheet restricts the attraction force (the magnet "punches through" it).
• Material composition – not every steel attracts identically. High carbon content worsen the interaction with the magnet.
• Surface condition – smooth surfaces guarantee perfect abutment, which increases force. Rough surfaces weaken the grip.
• Operating temperature – NdFeB sinters have a negative temperature coefficient. When it is hot they are weaker, and at low temperatures they can be stronger (up to a certain limit).

* Holding force was checked on a smooth steel plate of 20 mm thickness, when a perpendicular force was applied, whereas under attempts to slide the magnet the load capacity is reduced by as much as 5 times. Moreover, even a slight gap {between} the magnet and the plate lowers the lifting capacity.