MW 38x3.5 / N38 - cylindrical magnet

Advantages as well as disadvantages of neodymium magnets.

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

• They do not lose power, even over approximately 10 years – the decrease in power is only ~1% (theoretically),
• They do not lose their magnetic properties even under close interference source,
• In other words, due to the smooth layer of gold, the element gains a professional look,
• The surface of neodymium magnets generates a strong magnetic field – this is a key feature,
• Due to their durability and thermal resistance, neodymium magnets can operate (depending on the form) even at high temperatures reaching 230°C or more...
• Thanks to modularity in shaping and the capacity to customize to specific needs,
• Significant place in modern industrial fields – they serve a role in HDD drives, electric motors, precision medical tools, also modern systems.
• Thanks to efficiency per cm³, small magnets offer high operating force, in miniature format,

Disadvantages of NdFeB magnets:

• Susceptibility to cracking is one of their disadvantages. Upon intense impact they can break. We recommend keeping them in a steel housing, which not only secures them against impacts but also increases their durability
• NdFeB magnets demagnetize when exposed to high temperatures. After reaching 80°C, many of them experience permanent weakening of strength (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
• When exposed to humidity, magnets start to rust. To use them in conditions outside, it is recommended to use protective magnets, such as those in rubber or plastics, which secure oxidation and corrosion.
• Limited ability of producing threads in the magnet and complex shapes - preferred is a housing - magnetic holder.
• Possible danger related to microscopic parts of magnets are risky, when accidentally swallowed, which is particularly important in the context of child health protection. 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 contributes to it?

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

• using a sheet made of high-permeability steel, serving as a magnetic yoke
• with a thickness of at least 10 mm
• characterized by smoothness
• without any clearance between the magnet and steel
• under perpendicular force vector (90-degree angle)
• at temperature approx. 20 degrees Celsius

Determinants of lifting force in real conditions

In real-world applications, the actual holding force is determined by a number of factors, presented from most significant:

• Air gap (between the magnet and the metal), since even a microscopic clearance (e.g. 0.5 mm) can cause a decrease in lifting capacity by up to 50% (this also applies to paint, rust or dirt).
• Force direction – remember that the magnet has greatest strength perpendicularly. Under shear forces, the capacity drops drastically, often to levels of 20-30% of the maximum value.
• Metal thickness – thin material does not allow full use of the magnet. Magnetic flux passes through the material instead of generating force.
• Steel grade – the best choice is pure iron steel. Cast iron may attract less.
• Surface condition – ground elements guarantee perfect abutment, which improves field saturation. Uneven metal reduce efficiency.
• Heat – NdFeB sinters have a sensitivity to temperature. At higher temperatures they lose power, and in frost they can be stronger (up to a certain limit).

* Holding force was measured on the plate surface of 20 mm thickness, when a perpendicular force was applied, in contrast under shearing force the holding force is lower. Moreover, even a slight gap {between} the magnet and the plate reduces the lifting capacity.