SM 18x200 [2xM5] / N42 - magnetic separator

Advantages and disadvantages of rare earth magnets.

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

• They do not lose strength, even during approximately ten years – the drop in strength is only ~1% (according to tests),
• They are extremely resistant to demagnetization induced by external disturbances,
• By using a reflective layer of gold, the element acquires an elegant look,
• Magnets are distinguished by impressive magnetic induction on the working surface,
• Neodymium magnets are characterized by very high magnetic induction on the magnet surface and can function (depending on the shape) even at a temperature of 230°C or more...
• Thanks to flexibility in designing and the capacity to modify to complex applications,
• Wide application in innovative solutions – they find application in computer drives, brushless drives, medical devices, also multitasking production systems.
• Compactness – despite small sizes they offer powerful magnetic field, making them ideal for precision applications

Problematic aspects of neodymium magnets and proposals for their use:

• They are fragile upon heavy impacts. To avoid cracks, it is worth protecting magnets in a protective case. Such protection not only protects the magnet but also increases its resistance to damage
• Neodymium magnets lose power when exposed to high temperatures. After reaching 80°C, many of them experience permanent drop of power (a factor is the shape as well as dimensions of the magnet). We offer magnets specially adapted to work at temperatures up to 230°C marked [AH], which are extremely resistant to heat
• Due to the susceptibility of magnets to corrosion in a humid environment, we recommend using waterproof magnets made of rubber, plastic or other material resistant to moisture, in case of application outdoors
• Limited possibility of making nuts in the magnet and complex forms - preferred is a housing - mounting mechanism.
• Health risk resulting from small fragments of magnets are risky, in case of ingestion, which is particularly important in the context of child safety. It is also worth noting that tiny parts of these magnets are able to complicate diagnosis medical after entering the body.
• Higher cost of purchase is one of the disadvantages compared to ceramic magnets, especially in budget applications

Detachment force of the magnet in optimal conditions – what it depends on?

Breakaway force is the result of a measurement for the most favorable conditions, taking into account:

• on a block made of mild steel, perfectly concentrating the magnetic flux
• with a cross-section of at least 10 mm
• with an ideally smooth touching surface
• under conditions of ideal adhesion (surface-to-surface)
• under vertical application of breakaway force (90-degree angle)
• in temp. approx. 20°C

Lifting capacity in real conditions – factors

In practice, the actual lifting capacity results from many variables, listed from crucial:

• Distance – existence of any layer (paint, dirt, gap) acts as an insulator, which reduces power rapidly (even by 50% at 0.5 mm).
• Force direction – note that the magnet has greatest strength perpendicularly. Under sliding down, the capacity drops significantly, often to levels of 20-30% of the maximum value.
• Substrate thickness – for full efficiency, the steel must be sufficiently thick. Paper-thin metal limits the lifting capacity (the magnet "punches through" it).
• Material type – the best choice is pure iron steel. Stainless steels may attract less.
• Plate texture – ground elements guarantee perfect abutment, which improves force. Rough surfaces reduce efficiency.
• Temperature – heating the magnet results in weakening of induction. It is worth remembering the thermal limit for a given model.

* Holding force was checked on the plate surface of 20 mm thickness, when a perpendicular force was applied, in contrast under parallel forces the load capacity is reduced by as much as 75%. Moreover, even a minimal clearance {between} the magnet and the plate reduces the holding force.