SM 25x325 [2xM8] / N42 - magnetic separator

Strengths and weaknesses of neodymium magnets.

Besides their tremendous strength, neodymium magnets offer the following advantages:

• They retain magnetic properties for around 10 years – the loss is just ~1% (according to analyses),
• Magnets perfectly protect themselves against demagnetization caused by external fields,
• Thanks to the shiny finish, the surface of nickel, gold-plated, or silver gives an elegant appearance,
• Neodymium magnets generate maximum magnetic induction on a small area, which increases force concentration,
• Made from properly selected components, these magnets show impressive resistance to high heat, enabling them to function (depending on their shape) at temperatures up to 230°C and above...
• Thanks to the potential of flexible forming and adaptation to unique projects, magnetic components can be modeled in a broad palette of forms and dimensions, which amplifies use scope,
• Universal use in high-tech industry – they find application in HDD drives, motor assemblies, precision medical tools, and modern systems.
• Relatively small size with high pulling force – neodymium magnets offer strong magnetic field in tiny dimensions, which makes them useful in small systems

Cons 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.
• We warn that neodymium magnets can lose their strength at high temperatures. To prevent this, we suggest our specialized [AH] magnets, which work effectively even at 230°C.
• They oxidize in a humid environment. For use outdoors we suggest using waterproof magnets e.g. in rubber, plastic
• We suggest casing - magnetic mount, due to difficulties in producing threads inside the magnet and complicated shapes.
• Health risk resulting from small fragments of magnets can be dangerous, if swallowed, which is particularly important in the context of child safety. Additionally, tiny parts of these devices are able to complicate diagnosis medical after entering the body.
• High unit price – neodymium magnets have a higher price than other types of magnets (e.g. ferrite), which can limit application in large quantities

Breakaway strength of the magnet in ideal conditions – what affects it?

Breakaway force is the result of a measurement for ideal contact conditions, assuming:

• with the contact of a sheet made of special test steel, guaranteeing full magnetic saturation
• possessing a thickness of at least 10 mm to ensure full flux closure
• with a plane perfectly flat
• under conditions of gap-free contact (metal-to-metal)
• during detachment in a direction vertical to the mounting surface
• in temp. approx. 20°C

Determinants of lifting force in real conditions

It is worth knowing that the magnet holding may be lower depending on the following factors, in order of importance:

• Gap between magnet and steel – every millimeter of distance (caused e.g. by varnish or dirt) diminishes the pulling force, often by half at just 0.5 mm.
• Angle of force application – highest force is available only during perpendicular pulling. The resistance to sliding of the magnet along the plate is usually several times smaller (approx. 1/5 of the lifting capacity).
• Plate thickness – insufficiently thick plate causes magnetic saturation, causing part of the flux to be wasted into the air.
• Material composition – not every steel reacts the same. Alloy additives weaken the interaction with the magnet.
• Surface condition – smooth surfaces ensure maximum contact, which improves force. Uneven metal weaken the grip.
• Thermal factor – hot environment reduces magnetic field. Too high temperature can permanently demagnetize the magnet.

* Holding force was measured on the plate surface of 20 mm thickness, when the force acted perpendicularly, however under shearing force the lifting capacity is smaller. Additionally, even a slight gap {between} the magnet’s surface and the plate reduces the holding force.