SM 18x275 [2xM5] / N42 - magnetic separator

Advantages and disadvantages of neodymium magnets NdFeB.

In addition to their remarkable magnetic power, neodymium magnets offer the following advantages:

• They do not lose their even over approximately 10 years – the reduction of lifting capacity is only ~1% (according to tests),
• They are highly resistant to demagnetization caused by external magnetic fields,
• Because of the brilliant layer of gold, the component looks visually appealing,
• The outer field strength of the magnet shows advanced magnetic properties,
• With the right combination of magnetic alloys, they reach increased thermal stability, enabling operation at or above 230°C (depending on the design),
• With the option for fine forming and personalized design, these magnets can be produced in numerous shapes and sizes, greatly improving application potential,
• Important function in modern technologies – they find application in HDDs, electric drives, clinical machines along with high-tech tools,
• Relatively small size with high magnetic force – neodymium magnets offer strong power in small dimensions, which makes them ideal in compact constructions

Disadvantages of magnetic elements:

• They are fragile when subjected to a heavy impact. If the magnets are exposed to shocks, they should be placed in a protective case. The steel housing, in the form of a holder, protects the magnet from fracture and enhances its overall strength,
• They lose field intensity at elevated temperatures. Most neodymium magnets experience permanent loss in strength when heated above 80°C (depending on the geometry and height). However, we offer special variants with high temperature resistance that can operate up to 230°C or higher,
• Magnets exposed to humidity can oxidize. Therefore, for outdoor applications, it's best to use waterproof types made of rubber,
• Limited ability to create precision features in the magnet – the use of a housing is recommended,
• Possible threat related to magnet particles may arise, especially if swallowed, which is notable in the health of young users. Additionally, miniature parts from these magnets might complicate medical imaging when ingested,
• Due to the price of neodymium, their cost is above average,

Best holding force of the magnet in ideal parameters – what affects it?

The given strength of the magnet corresponds to the optimal strength, calculated under optimal conditions, that is:

• with mild steel, serving as a magnetic flux conductor
• of a thickness of at least 10 mm
• with a refined outer layer
• with zero air gap
• in a perpendicular direction of force
• under standard ambient temperature

Lifting capacity in real conditions – factors

Practical lifting force is determined by factors, listed from the most critical to the less significant:

• Air gap between the magnet and the plate, because even a very small distance (e.g. 0.5 mm) causes a drop in lifting force of up to 50%.
• Direction of applied force, because the maximum lifting capacity is achieved under perpendicular application. The force required to slide the magnet along the plate is usually several times lower.
• Thickness of the plate, as a plate that is too thin causes part of the magnetic flux not to be used and to remain wasted in the air.
• Material of the plate, because higher carbon content lowers holding force, while higher iron content increases it. The best choice is steel with high magnetic permeability and high saturation induction.
• Surface of the plate, because the more smooth and polished it is, the better the contact and consequently the greater the magnetic saturation.
• Operating temperature, since all permanent magnets have a negative temperature coefficient. This means that at high temperatures they are weaker, while at sub-zero temperatures they become slightly stronger.

* Holding force was checked on a smooth steel plate of 20 mm thickness, when the force acted perpendicularly, whereas under parallel forces the load capacity is reduced by as much as fivefold. In addition, even a minimal clearance {between} the magnet’s surface and the plate lowers the lifting capacity.