UMP 97x40 [M8+M10] GW F300 kg / N38 - search holder

Strengths and weaknesses of rare earth magnets.

Besides their high retention, neodymium magnets are valued for these benefits:

• They do not lose strength, even after approximately ten years – the reduction in lifting capacity is only ~1% (according to tests),
• They are resistant to demagnetization induced by external magnetic fields,
• In other words, due to the shiny layer of nickel, the element looks attractive,
• They feature high magnetic induction at the operating surface, which increases their power,
• Through (appropriate) combination of ingredients, they can achieve high thermal strength, enabling functioning at temperatures reaching 230°C and above...
• Thanks to versatility in designing and the capacity to modify to specific needs,
• Huge importance in electronics industry – they are commonly used in HDD drives, electric motors, diagnostic systems, also other advanced devices.
• Relatively small size with high pulling force – neodymium magnets offer high power in tiny dimensions, which makes them useful in compact constructions

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

• To avoid cracks upon strong impacts, we suggest using special steel housings. Such a solution protects the magnet and simultaneously increases its durability.
• Neodymium magnets lose force when exposed to high temperatures. After reaching 80°C, many of them experience permanent drop of power (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 rust. Therefore while using outdoors, we suggest using water-impermeable magnets made of rubber, plastic or other material protecting against moisture
• We recommend casing - magnetic mechanism, due to difficulties in realizing nuts inside the magnet and complicated forms.
• Possible danger to health – tiny shards of magnets are risky, in case of ingestion, which is particularly important in the aspect of protecting the youngest. Additionally, small components of these products can disrupt the diagnostic process medical when they are in the body.
• High unit price – neodymium magnets are more expensive than other types of magnets (e.g. ferrite), which can limit application in large quantities

Maximum lifting force for a neodymium magnet – what it depends on?

The load parameter shown 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
• with a cross-section minimum 10 mm
• with a surface free of scratches
• with direct contact (no paint)
• during pulling in a direction perpendicular to the mounting surface
• at temperature room level

Determinants of practical lifting force of a magnet

Holding efficiency is affected by specific conditions, including (from most important):

• Gap between surfaces – every millimeter of separation (caused e.g. by veneer or unevenness) diminishes the magnet efficiency, often by half at just 0.5 mm.
• Loading method – declared lifting capacity refers to detachment vertically. When slipping, the magnet exhibits significantly lower power (often approx. 20-30% of nominal force).
• Steel thickness – insufficiently thick steel causes magnetic saturation, causing part of the flux to be wasted into the air.
• Material type – the best choice is pure iron steel. Stainless steels may generate lower lifting capacity.
• Smoothness – ideal contact is possible only on polished steel. Rough texture reduce the real contact area, weakening the magnet.
• Temperature influence – high temperature weakens pulling force. Too high temperature can permanently demagnetize the magnet.

* Holding force was measured on a smooth steel plate of 20 mm thickness, when a perpendicular force was applied, in contrast under shearing force the holding force is lower. In addition, even a slight gap {between} the magnet and the plate lowers the load capacity.