SMZR 32x200 / N52 - magnetic separator with handle

Advantages as well as disadvantages of neodymium magnets NdFeB.

In addition to their immense pulling force, neodymium magnets offer the following advantages:

• They virtually do not lose power, because even after ten years, the performance loss is only ~1% (based on calculations),
• They remain magnetized despite exposure to magnetic noise,
• Because of the reflective layer of silver, the component looks visually appealing,
• The outer field strength of the magnet shows remarkable magnetic properties,
• With the right combination of magnetic alloys, they reach significant thermal stability, enabling operation at or above 230°C (depending on the design),
• With the option for fine forming and personalized design, these magnets can be produced in multiple shapes and sizes, greatly improving engineering flexibility,
• Important function in modern technologies – they serve a purpose in hard drives, rotating machines, diagnostic apparatus as well as sophisticated instruments,
• Compactness – despite their small size, they deliver powerful magnetism, making them ideal for precision applications

Disadvantages of rare earth magnets:

• They may fracture when subjected to a powerful impact. If the magnets are exposed to external force, it is suggested to place them in a protective enclosure. The steel housing, in the form of a holder, protects the magnet from breakage , and at the same time enhances its overall resistance,
• They lose magnetic force at high temperatures. Most neodymium magnets experience permanent loss in strength when heated above 80°C (depending on the geometry and height). However, we offer special variants with high temperature resistance that can operate up to 230°C or higher,
• They rust in a moist environment. For outdoor use, we recommend using waterproof magnets, such as those made of non-metallic materials,
• The use of a protective casing or external holder is recommended, since machining fine details in neodymium magnets is difficult,
• Safety concern related to magnet particles may arise, if ingested accidentally, which is crucial in the health of young users. Furthermore, minuscule fragments from these products have the potential to interfere with diagnostics after being swallowed,
• Due to the price of neodymium, their cost is considerably higher,

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

The given holding capacity of the magnet corresponds to the highest holding force, measured under optimal conditions, specifically:

• with the use of low-carbon steel plate serving as a magnetic yoke
• having a thickness of no less than 10 millimeters
• with a smooth surface
• with zero air gap
• under perpendicular detachment force
• in normal thermal conditions

Key elements affecting lifting force

Practical lifting force is dependent on factors, listed from the most critical to the less significant:

• Air gap between the magnet and the plate, since 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.

* Lifting capacity testing was carried out on plates with a smooth surface of suitable thickness, under a perpendicular pulling force, whereas under attempts to slide the magnet the holding force is lower. In addition, even a small distance {between} the magnet’s surface and the plate decreases the load capacity.