MPL 30x20x5 / N38 - lamellar magnet

Advantages and disadvantages of neodymium magnets NdFeB.

In addition to their tremendous magnetic power, neodymium magnets offer the following advantages:

• They have unchanged lifting capacity, and over more than ten years their attraction force decreases symbolically – ~1% (in testing),
• They remain magnetized despite exposure to strong external fields,
• The use of a mirror-like gold surface provides a eye-catching finish,
• They have very high magnetic induction on the surface of the magnet,
• These magnets tolerate elevated temperatures, often exceeding 230°C, when properly designed (in relation to build),
• The ability for accurate shaping or customization to specific needs – neodymium magnets can be manufactured in many forms and dimensions, which amplifies their functionality across industries,
• Important function in new technology industries – they find application in HDDs, electric drives, diagnostic apparatus and sophisticated instruments,
• Thanks to their power density, small magnets offer high magnetic performance, in miniature format,

Disadvantages of NdFeB magnets:

• They are prone to breaking when subjected to a sudden 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 breakage and enhances its overall durability,
• They lose power at extreme temperatures. Most neodymium magnets experience permanent loss in strength when heated above 80°C (depending on the dimensions and height). However, we offer special variants with high temperature resistance that can operate up to 230°C or higher,
• They rust in a wet environment. For outdoor use, we recommend using sealed magnets, such as those made of rubber,
• Limited ability to create complex details in the magnet – the use of a external casing is recommended,
• Health risk from tiny pieces may arise, especially if swallowed, which is crucial in the family environments. It should also be noted that tiny components from these products have the potential to hinder health screening after being swallowed,
• High unit cost – neodymium magnets are pricier than other types of magnets (e.g., ferrite), which increases the cost of large-scale applications

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

The given holding capacity of the magnet represents the highest holding force, assessed under optimal conditions, that is:

• with mild steel, serving as a magnetic flux conductor
• of a thickness of at least 10 mm
• with a refined outer layer
• with zero air gap
• with vertical force applied
• under standard ambient temperature

What influences lifting capacity in practice

In practice, the holding capacity of a magnet is affected by these factors, arranged from the most important to the least relevant:

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

* Holding force was tested on the plate surface of 20 mm thickness, when a perpendicular force was applied, however under shearing force the load capacity is reduced by as much as fivefold. In addition, even a small distance {between} the magnet and the plate reduces the load capacity.