MW 10x4 / N38 - cylindrical magnet

Advantages as well as disadvantages of neodymium magnets NdFeB.

Apart from their superior holding force, neodymium magnets have these key benefits:

• Their strength remains stable, and after approximately 10 years, it drops only by ~1% (theoretically),
• They are extremely resistant to demagnetization caused by external magnetic sources,
• In other words, due to the glossy nickel coating, the magnet obtains an stylish appearance,
• They possess intense magnetic force measurable at the magnet’s surface,
• Thanks to their enhanced temperature resistance, they can operate (depending on the shape) even at temperatures up to 230°C or more,
• With the option for fine forming and precise design, these magnets can be produced in various shapes and sizes, greatly improving application potential,
• Wide application in advanced technical fields – they find application in data storage devices, electric motors, clinical machines along with technologically developed systems,
• Compactness – despite their small size, they generate strong force, making them ideal for precision applications

Disadvantages of NdFeB magnets:

• They may fracture when subjected to a heavy impact. If the magnets are exposed to physical collisions, they should be placed in a metal holder. The steel housing, in the form of a holder, protects the magnet from fracture while also reinforces its overall strength,
• Magnets lose field strength when exposed to temperatures exceeding 80°C. In most cases, this leads to irreversible performance loss (influenced by the magnet’s dimensions). To address this, we provide [AH] models with superior thermal resistance, able to operate even at 230°C or more,
• They rust in a moist environment. For outdoor use, we recommend using sealed magnets, such as those made of polymer,
• The use of a protective casing or external holder is recommended, since machining fine details in neodymium magnets is not feasible,
• Health risk related to magnet particles may arise, when consumed by mistake, which is crucial in the context of child safety. Additionally, minuscule fragments from these devices might disrupt scanning after being swallowed,
• Higher purchase price is one of the drawbacks compared to ceramic magnets, especially in budget-sensitive applications

Detachment force of the magnet in optimal conditions – what contributes to it?

The given holding capacity of the magnet corresponds to the highest holding force, measured in ideal conditions, namely:

• using a steel plate with low carbon content, serving as a magnetic circuit closure
• with a thickness of minimum 10 mm
• with a smooth surface
• with zero air gap
• with vertical force applied
• at room temperature

Magnet lifting force in use – key factors

The lifting capacity of a magnet is determined by in practice the following factors, according to their importance:

• Air gap between the magnet and the plate, as 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 measured by applying a steel plate with a smooth surface of suitable thickness (min. 20 mm), under perpendicular pulling force, whereas under attempts to slide the magnet the holding force is lower. Moreover, even a slight gap {between} the magnet’s surface and the plate decreases the load capacity.