MPL 50x30x4 / N38 - lamellar magnet

Advantages as well as disadvantages of neodymium magnets NdFeB.

In addition to their long-term stability, neodymium magnets provide the following advantages:

• They retain their attractive force for around ten years – the loss is just ~1% (in theory),
• They show superior resistance to demagnetization from external magnetic fields,
• The use of a decorative nickel surface provides a eye-catching finish,
• They possess intense magnetic force measurable at the magnet’s surface,
• With the right combination of magnetic alloys, they reach increased 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,
• Significant impact in advanced technical fields – they serve a purpose in hard drives, electric motors, clinical machines and other advanced devices,
• Thanks to their concentrated strength, small magnets offer high magnetic performance, in miniature format,

Disadvantages of rare earth magnets:

• They may fracture when subjected to a heavy impact. If the magnets are exposed to external force, it is advisable to use in a steel housing. The steel housing, in the form of a holder, protects the magnet from damage and strengthens its overall resistance,
• They lose strength at extreme temperatures. Most neodymium magnets experience permanent degradation 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, especially when used outside, we recommend using sealed magnets, such as those made of plastic,
• The use of a protective casing or external holder is recommended, since machining internal cuts in neodymium magnets is not feasible,
• Health risk due to small fragments may arise, when consumed by mistake, which is crucial in the family environments. Moreover, small elements from these products might hinder health screening if inside the body,
• Due to expensive raw materials, their cost is considerably higher,

Maximum magnetic pulling force – what affects it?

The given strength of the magnet means the optimal strength, determined under optimal conditions, specifically:

• with the use of low-carbon steel plate acting as a magnetic yoke
• with a thickness of minimum 10 mm
• with a polished side
• with zero air gap
• in a perpendicular direction of force
• under standard ambient temperature

What influences lifting capacity in practice

Practical lifting force is dependent on elements, 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) can cause 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 was assessed with the use of a smooth steel plate of suitable thickness (min. 20 mm), under perpendicular pulling force, however under shearing force the lifting capacity is smaller. In addition, even a slight gap {between} the magnet’s surface and the plate decreases the holding force.