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

Strengths and weaknesses of neodymium magnets.

Besides their immense pulling force, neodymium magnets offer the following advantages:

• Their magnetic field is maintained, and after approximately 10 years it decreases only by ~1% (theoretically),
• They are resistant to demagnetization induced by presence of other magnetic fields,
• The use of an metallic coating of noble metals (nickel, gold, silver) causes the element to look better,
• They show high magnetic induction at the operating surface, which affects their effectiveness,
• Thanks to resistance to high temperature, they can operate (depending on the form) even at temperatures up to 230°C and higher...
• Possibility of individual creating as well as optimizing to concrete requirements,
• Wide application in innovative solutions – they are used in hard drives, electromotive mechanisms, medical devices, as well as complex engineering applications.
• Thanks to concentrated force, small magnets offer high operating force, in miniature format,

Disadvantages of neodymium magnets:

• They are prone to damage upon heavy impacts. To avoid cracks, it is worth securing magnets in special housings. Such protection not only protects the magnet but also improves its resistance to damage
• We warn that neodymium magnets can reduce their strength at high temperatures. To prevent this, we advise our specialized [AH] magnets, which work effectively even at 230°C.
• Due to the susceptibility of magnets to corrosion in a humid environment, we recommend using waterproof magnets made of rubber, plastic or other material stable to moisture, in case of application outdoors
• We recommend a housing - magnetic mechanism, due to difficulties in realizing threads inside the magnet and complex forms.
• Potential hazard to health – tiny shards of magnets pose a threat, in case of ingestion, which is particularly important in the aspect of protecting the youngest. Additionally, tiny parts of these magnets can be problematic in diagnostics medical in case of swallowing.
• With budget limitations the cost of neodymium magnets is economically unviable,

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

Holding force of 0 kg is a theoretical maximum value conducted under standard conditions:

• using a sheet made of low-carbon steel, acting as a ideal flux conductor
• whose thickness reaches at least 10 mm
• with a surface cleaned and smooth
• with zero gap (without paint)
• under vertical force vector (90-degree angle)
• at standard ambient temperature

Practical aspects of lifting capacity – factors

Holding efficiency is affected by working environment parameters, such as (from most important):

• Space between magnet and steel – even a fraction of a millimeter of distance (caused e.g. by varnish or unevenness) diminishes the magnet efficiency, often by half at just 0.5 mm.
• Load vector – highest force is obtained only during pulling at a 90° angle. The resistance to sliding of the magnet along the plate is usually several times smaller (approx. 1/5 of the lifting capacity).
• Substrate thickness – for full efficiency, the steel must be sufficiently thick. Thin sheet restricts the attraction force (the magnet "punches through" it).
• Plate material – low-carbon steel gives the best results. Alloy steels decrease magnetic permeability and lifting capacity.
• Surface finish – full contact is obtained only on smooth steel. Any scratches and bumps create air cushions, weakening the magnet.
• Heat – neodymium magnets have a sensitivity to temperature. At higher temperatures they are weaker, and in frost they can be stronger (up to a certain limit).

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