BM 650x180x70 [4x M8] - magnetic beam

Strengths as well as weaknesses of rare earth magnets.

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

• Their power remains stable, and after approximately ten years it drops only by ~1% (theoretically),
• Neodymium magnets are extremely resistant to magnetic field loss caused by external magnetic fields,
• In other words, due to the reflective layer of silver, the element gains a professional look,
• Neodymium magnets achieve maximum magnetic induction on a their surface, which increases force concentration,
• Thanks to resistance to high temperature, they are capable of working (depending on the form) even at temperatures up to 230°C and higher...
• Due to the possibility of free molding and customization to unique requirements, magnetic components can be created in a broad palette of geometric configurations, which increases their versatility,
• Huge importance in electronics industry – they are used in computer drives, electric motors, medical devices, also modern systems.
• Thanks to their power density, small magnets offer high operating force, in miniature format,

Characteristics of disadvantages of neodymium magnets and proposals for their use:

• To avoid cracks upon strong impacts, we recommend using special steel housings. Such a solution secures the magnet and simultaneously increases its durability.
• NdFeB magnets lose strength when exposed to high temperatures. After reaching 80°C, many of them experience permanent weakening of strength (a factor is the shape as well as dimensions of the magnet). We offer magnets specially adapted to work at temperatures up to 230°C marked [AH], which are very resistant to heat
• Magnets exposed to a humid environment can corrode. Therefore when using outdoors, we advise using water-impermeable magnets made of rubber, plastic or other material protecting against moisture
• Due to limitations in producing threads and complicated forms in magnets, we propose using casing - magnetic holder.
• Health risk to health – tiny shards of magnets are risky, in case of ingestion, which gains importance in the context of child safety. It is also worth noting that small elements of these magnets are able to disrupt the diagnostic process medical in case of swallowing.
• High unit price – neodymium magnets have a higher price than other types of magnets (e.g. ferrite), which increases costs of application in large quantities

Maximum lifting capacity of the magnet – what affects it?

Breakaway force was determined for ideal contact conditions, assuming:

• using a plate made of mild steel, serving as a ideal flux conductor
• with a cross-section minimum 10 mm
• with an ground touching surface
• with total lack of distance (without coatings)
• under vertical force direction (90-degree angle)
• at ambient temperature approx. 20 degrees Celsius

Key elements affecting lifting force

During everyday use, the actual holding force results from a number of factors, listed from crucial:

• Gap between magnet and steel – every millimeter of separation (caused e.g. by varnish or dirt) drastically reduces the magnet efficiency, often by half at just 0.5 mm.
• Loading method – declared lifting capacity refers to detachment vertically. When applying parallel force, the magnet holds much less (often approx. 20-30% of nominal force).
• Substrate thickness – to utilize 100% power, the steel must be adequately massive. Thin sheet restricts the lifting capacity (the magnet "punches through" it).
• Chemical composition of the base – low-carbon steel gives the best results. Alloy admixtures reduce magnetic properties and holding force.
• Surface condition – smooth surfaces ensure maximum contact, which increases field saturation. Rough surfaces reduce efficiency.
• Temperature influence – high temperature reduces pulling force. Too high temperature can permanently demagnetize the magnet.

* Lifting capacity testing was conducted on plates with a smooth surface of suitable thickness, under a perpendicular pulling force, however under shearing force the holding force is lower. Additionally, even a slight gap {between} the magnet and the plate reduces the lifting capacity.