SM 25x350 [2xM8] / N42 - magnetic separator

Advantages and disadvantages of neodymium magnets NdFeB.

In addition to their pulling strength, neodymium magnets provide the following advantages:

• Their magnetic field remains stable, and after around 10 years, it drops only by ~1% (according to research),
• They show exceptional resistance to demagnetization from external field exposure,
• By applying a bright layer of nickel, the element gains a sleek look,
• The outer field strength of the magnet shows remarkable magnetic properties,
• These magnets tolerate high temperatures, often exceeding 230°C, when properly designed (in relation to build),
• With the option for customized forming and targeted design, these magnets can be produced in numerous shapes and sizes, greatly improving design adaptation,
• Wide application in advanced technical fields – they serve a purpose in HDDs, electric motors, medical equipment as well as other advanced devices,
• Thanks to their concentrated strength, small magnets offer high magnetic performance, in miniature format,

Disadvantages of magnetic elements:

• They can break when subjected to a strong impact. If the magnets are exposed to external force, it is advisable to use in a metal holder. The steel housing, in the form of a holder, protects the magnet from cracks , and at the same time strengthens its overall strength,
• They lose magnetic force at high temperatures. Most neodymium magnets experience permanent loss in strength when heated above 80°C (depending on the shape and height). However, we offer special variants with high temperature resistance that can operate up to 230°C or higher,
• Magnets exposed to wet conditions can rust. Therefore, for outdoor applications, we suggest waterproof types made of plastic,
• Limited ability to create precision features in the magnet – the use of a housing is recommended,
• Possible threat from tiny pieces may arise, when consumed by mistake, which is important in the protection of children. Additionally, tiny components from these devices can hinder health screening if inside the body,
• Due to a complex production process, their cost is considerably higher,

Maximum magnetic pulling force – what contributes to it?

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

• with mild steel, serving as a magnetic flux conductor
• of a thickness of at least 10 mm
• with a polished side
• with zero air gap
• under perpendicular detachment force
• at room temperature

Lifting capacity in real conditions – factors

In practice, the holding capacity of a magnet is affected by these factors, in descending order of importance:

• 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 measured on the plate surface of 20 mm thickness, when the force acted perpendicularly, in contrast under parallel forces the load capacity is reduced by as much as fivefold. Additionally, even a small distance {between} the magnet’s surface and the plate reduces the holding force.