MW 29x10 / N38 - cylindrical magnet

Advantages as well as disadvantages of rare earth magnets.

Besides their remarkable field intensity, neodymium magnets offer the following advantages:

• They retain magnetic properties for nearly ten years – the loss is just ~1% (based on simulations),
• They maintain their magnetic properties even under external field action,
• The use of an shiny layer of noble metals (nickel, gold, silver) causes the element to be more visually attractive,
• Neodymium magnets ensure maximum magnetic induction on a small surface, which allows for strong attraction,
• Through (adequate) combination of ingredients, they can achieve high thermal resistance, enabling action at temperatures approaching 230°C and above...
• Thanks to freedom in shaping and the ability to customize to specific needs,
• Fundamental importance in electronics industry – they are utilized in mass storage devices, brushless drives, diagnostic systems, as well as modern systems.
• Compactness – despite small sizes they offer powerful magnetic field, making them ideal for precision applications

Problematic aspects of neodymium magnets and proposals for their use:

• At strong impacts they can break, therefore we advise placing them in strong housings. A metal housing provides additional protection against damage and increases the magnet's durability.
• Neodymium magnets decrease their force under the influence of heating. As soon as 80°C is exceeded, many of them start losing their power. Therefore, we recommend our special magnets marked [AH], which maintain durability even at temperatures up to 230°C
• When exposed to humidity, magnets start to rust. To use them in conditions outside, it is recommended to use protective magnets, such as magnets in rubber or plastics, which secure oxidation and corrosion.
• Limited possibility of making threads in the magnet and complicated forms - preferred is a housing - magnetic holder.
• Potential hazard resulting from small fragments of magnets pose a threat, in case of ingestion, which becomes key in the aspect of protecting the youngest. It is also worth noting that tiny parts of these products can disrupt the diagnostic process medical in case of swallowing.
• Due to neodymium price, their price is higher than average,

Maximum holding power of the magnet – what it depends on?

The specified lifting capacity represents the peak performance, measured under optimal environment, namely:

• with the application of a yoke made of low-carbon steel, guaranteeing maximum field concentration
• with a thickness of at least 10 mm
• with an ground contact surface
• with total lack of distance (without impurities)
• for force acting at a right angle (pull-off, not shear)
• at ambient temperature room level

Magnet lifting force in use – key factors

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

• Space between magnet and steel – every millimeter of distance (caused e.g. by varnish or dirt) diminishes the magnet efficiency, often by half at just 0.5 mm.
• Pull-off angle – remember that the magnet has greatest strength perpendicularly. Under shear forces, the holding force drops significantly, 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 lifting capacity (the magnet "punches through" it).
• Chemical composition of the base – mild steel gives the best results. Higher carbon content reduce magnetic permeability and holding force.
• Surface quality – the more even the plate, the larger the contact zone and stronger the hold. Unevenness creates an air distance.
• Thermal environment – temperature increase causes a temporary drop of induction. Check the thermal limit for a given model.

* Lifting capacity was assessed using a smooth steel plate of optimal thickness (min. 20 mm), under perpendicular pulling force, however under attempts to slide the magnet the lifting capacity is smaller. Moreover, even a minimal clearance {between} the magnet’s surface and the plate decreases the lifting capacity.