SM 25x150 [2xM8] / N42 - magnetic separator

Strengths as well as weaknesses of rare earth magnets.

In addition to their magnetic capacity, neodymium magnets provide the following advantages:

• They have unchanged lifting capacity, and over more than ten years their performance decreases symbolically – ~1% (in testing),
• Magnets very well defend themselves against demagnetization caused by ambient magnetic noise,
• By applying a reflective layer of gold, the element has an modern look,
• The surface of neodymium magnets generates a concentrated magnetic field – this is a key feature,
• 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 ability of flexible shaping and customization to unique projects, neodymium magnets can be produced in a variety of shapes and sizes, which increases their versatility,
• Universal use in innovative solutions – they serve a role in mass storage devices, electromotive mechanisms, advanced medical instruments, as well as industrial machines.
• Relatively small size with high pulling force – neodymium magnets offer impressive pulling force in compact dimensions, which enables their usage in small systems

Drawbacks and weaknesses of neodymium magnets: weaknesses and usage proposals

• Brittleness is one of their disadvantages. Upon intense impact they can break. We advise keeping them in a strong case, which not only secures them against impacts but also increases their durability
• Neodymium magnets lose their strength under the influence of heating. As soon as 80°C is exceeded, many of them start losing their force. Therefore, we recommend our special magnets marked [AH], which maintain durability even at temperatures up to 230°C
• They rust in a humid environment. For use outdoors we recommend using waterproof magnets e.g. in rubber, plastic
• We suggest a housing - magnetic mechanism, due to difficulties in producing threads inside the magnet and complex shapes.
• Potential hazard related to microscopic parts of magnets can be dangerous, in case of ingestion, which gains importance in the context of child health protection. Furthermore, tiny parts of these magnets are able to disrupt the diagnostic process medical when they are in the body.
• Due to neodymium price, their price is higher than average,

Maximum lifting capacity of the magnet – what contributes to it?

Breakaway force was determined for optimal configuration, including:

• with the contact of a sheet made of special test steel, ensuring full magnetic saturation
• possessing a thickness of min. 10 mm to ensure full flux closure
• with an ideally smooth touching surface
• under conditions of gap-free contact (metal-to-metal)
• under vertical application of breakaway force (90-degree angle)
• in temp. approx. 20°C

Lifting capacity in practice – influencing factors

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

• Clearance – the presence of any layer (paint, tape, air) interrupts the magnetic circuit, which reduces capacity steeply (even by 50% at 0.5 mm).
• Load vector – maximum parameter is obtained only during perpendicular pulling. The shear force of the magnet along the plate is typically several times smaller (approx. 1/5 of the lifting capacity).
• Base massiveness – insufficiently thick sheet does not close the flux, causing part of the flux to be lost into the air.
• Material type – the best choice is high-permeability steel. Hardened steels may generate lower lifting capacity.
• Plate texture – ground elements guarantee perfect abutment, which increases force. Uneven metal weaken the grip.
• Heat – neodymium magnets have a negative temperature coefficient. At higher temperatures they lose power, and at low temperatures they can be stronger (up to a certain limit).

* Holding force was measured on the plate surface of 20 mm thickness, when a perpendicular force was applied, whereas under attempts to slide the magnet the lifting capacity is smaller. Additionally, even a slight gap {between} the magnet’s surface and the plate decreases the load capacity.