BM 950x180x70 [4x M8] - magnetic beam

Strengths and weaknesses of neodymium magnets.

Besides their remarkable pulling force, neodymium magnets offer the following advantages:

• They do not lose magnetism, even over approximately ten years – the drop in strength is only ~1% (based on measurements),
• They are resistant to demagnetization induced by external field influence,
• A magnet with a metallic gold surface has an effective appearance,
• They feature high magnetic induction at the operating surface, which affects their effectiveness,
• Due to their durability and thermal resistance, neodymium magnets can operate (depending on the form) even at high temperatures reaching 230°C or more...
• Thanks to the possibility of free molding and customization to individualized needs, magnetic components can be modeled in a broad palette of geometric configurations, which expands the range of possible applications,
• Universal use in electronics industry – they find application in mass storage devices, electromotive mechanisms, diagnostic systems, and complex engineering applications.
• Thanks to their power density, small magnets offer high operating force, in miniature format,

Drawbacks and weaknesses of neodymium magnets and proposals for their use:

• They are prone to damage upon too strong impacts. To avoid cracks, it is worth protecting magnets in a protective case. Such protection not only protects the magnet but also improves its resistance to damage
• NdFeB magnets lose force when exposed to high temperatures. After reaching 80°C, many of them experience permanent drop of strength (a factor is the shape and 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
• When exposed to humidity, magnets start to rust. For applications outside, it is recommended to use protective magnets, such as magnets in rubber or plastics, which prevent oxidation and corrosion.
• Due to limitations in producing threads and complicated forms in magnets, we propose using cover - magnetic mechanism.
• Potential hazard resulting from small fragments of magnets can be dangerous, if swallowed, which gains importance in the context of child health protection. Additionally, small elements of these products can be problematic in diagnostics medical after entering the body.
• Higher cost of purchase is one of the disadvantages compared to ceramic magnets, especially in budget applications

Magnetic strength at its maximum – what contributes to it?

The declared magnet strength concerns the limit force, measured under ideal test conditions, specifically:

• using a plate made of low-carbon steel, acting as a magnetic yoke
• possessing a massiveness of min. 10 mm to ensure full flux closure
• with a surface free of scratches
• without any air gap between the magnet and steel
• during pulling in a direction perpendicular to the mounting surface
• at ambient temperature approx. 20 degrees Celsius

Key elements affecting lifting force

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

• Gap between surfaces – every millimeter of distance (caused e.g. by varnish or dirt) significantly weakens the pulling force, often by half at just 0.5 mm.
• Direction of force – maximum parameter is reached only during pulling at a 90° angle. The force required to slide of the magnet along the plate is standardly several times smaller (approx. 1/5 of the lifting capacity).
• Base massiveness – insufficiently thick plate does not close the flux, causing part of the flux to be wasted to the other side.
• Material type – ideal substrate is high-permeability steel. Hardened steels may generate lower lifting capacity.
• Surface finish – full contact is obtained only on polished steel. Rough texture create air cushions, weakening the magnet.
• Operating temperature – neodymium magnets have a sensitivity to temperature. At higher temperatures they lose power, and at low temperatures they can be stronger (up to a certain limit).

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