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

Strengths and weaknesses of NdFeB magnets.

Besides their high retention, neodymium magnets are valued for these benefits:

• They have stable power, and over more than 10 years their performance decreases symbolically – ~1% (in testing),
• They possess excellent resistance to magnetic field loss due to opposing magnetic fields,
• In other words, due to the aesthetic layer of silver, the element gains a professional look,
• The surface of neodymium magnets generates a powerful magnetic field – this is one of their assets,
• Due to their durability and thermal resistance, neodymium magnets can operate (depending on the shape) even at high temperatures reaching 230°C or more...
• Considering the potential of flexible shaping and adaptation to specialized requirements, NdFeB magnets can be produced in a broad palette of forms and dimensions, which expands the range of possible applications,
• Wide application in innovative solutions – they are utilized in computer drives, electric drive systems, medical equipment, also other advanced devices.
• Thanks to efficiency per cm³, small magnets offer high operating force, occupying minimum space,

Cons of neodymium magnets and proposals for their use:

• Susceptibility to cracking is one of their disadvantages. Upon intense impact they can fracture. We advise keeping them in a strong case, which not only protects them against impacts but also increases their durability
• When exposed to high temperature, neodymium magnets experience a drop in force. Often, when the temperature exceeds 80°C, their strength decreases (depending on the size, as well as shape of the magnet). For those who need magnets for extreme conditions, we offer [AH] versions withstanding up to 230°C
• They oxidize in a humid environment. For use outdoors we suggest using waterproof magnets e.g. in rubber, plastic
• Limited ability of making threads in the magnet and complex forms - recommended is a housing - magnet mounting.
• Possible danger to health – tiny shards of magnets can be dangerous, in case of ingestion, which is particularly important in the context of child safety. Additionally, tiny parts of these products can be problematic in diagnostics medical after entering the body.
• Higher cost of purchase is a significant factor to consider compared to ceramic magnets, especially in budget applications

Magnetic strength at its maximum – what contributes to it?

The force parameter is a result of laboratory testing executed under the following configuration:

• with the contact of a yoke made of low-carbon steel, ensuring maximum field concentration
• possessing a thickness of at least 10 mm to avoid saturation
• with a plane perfectly flat
• with direct contact (without impurities)
• for force applied at a right angle (pull-off, not shear)
• at temperature approx. 20 degrees Celsius

Practical aspects of lifting capacity – factors

Bear in mind that the magnet holding may be lower subject to elements below, in order of importance:

• Space between surfaces – even a fraction of a millimeter of distance (caused e.g. by varnish or unevenness) diminishes the pulling force, often by half at just 0.5 mm.
• Loading method – catalog parameter refers to pulling vertically. When slipping, the magnet exhibits significantly lower power (often approx. 20-30% of maximum force).
• Substrate thickness – for full efficiency, the steel must be adequately massive. Paper-thin metal restricts the attraction force (the magnet "punches through" it).
• Material composition – different alloys reacts the same. High carbon content worsen the interaction with the magnet.
• Surface structure – the more even the surface, the better the adhesion and higher the lifting capacity. Unevenness acts like micro-gaps.
• Thermal environment – temperature increase causes a temporary drop of force. It is worth remembering the maximum operating temperature for a given model.

* Lifting capacity was assessed with the use of a smooth steel plate of optimal thickness (min. 20 mm), under perpendicular detachment force, whereas under parallel forces the holding force is lower. Moreover, even a small distance {between} the magnet and the plate decreases the holding force.