SM 25x350 [2xM8] / N52 - magnetic separator

Advantages as well as disadvantages of neodymium magnets NdFeB.

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

• They have unchanged lifting capacity, and over nearly 10 years their performance decreases symbolically – ~1% (according to theory),
• They are very resistant to demagnetization caused by external magnetic sources,
• Because of the brilliant layer of gold, the component looks aesthetically refined,
• The outer field strength of the magnet shows remarkable magnetic properties,
• These magnets tolerate extreme temperatures, often exceeding 230°C, when properly designed (in relation to build),
• Thanks to the flexibility in shaping and the capability to adapt to individual requirements, neodymium magnets can be created in diverse shapes and sizes, which broadens their functional possibilities,
• Important function in advanced technical fields – they find application in hard drives, electromechanical systems, diagnostic apparatus and technologically developed systems,
• Relatively small size with high magnetic force – neodymium magnets offer strong power in tiny dimensions, which makes them ideal in compact constructions

Disadvantages of magnetic elements:

• They are prone to breaking when subjected to a strong 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 cracks , and at the same time strengthens its overall strength,
• Magnets lose field strength when exposed to temperatures exceeding 80°C. In most cases, this leads to irreversible magnetic decay (influenced by the magnet’s profile). To address this, we provide [AH] models with superior thermal resistance, able to operate even at 230°C or more,
• Magnets exposed to damp air can degrade. Therefore, for outdoor applications, it's best to use waterproof types made of rubber,
• Limited ability to create complex details in the magnet – the use of a mechanical support is recommended,
• Safety concern linked to microscopic shards may arise, especially if swallowed, which is crucial in the context of child safety. It should also be noted that miniature parts from these magnets can disrupt scanning once in the system,
• High unit cost – neodymium magnets are costlier than other types of magnets (e.g., ferrite), which increases the cost of large-scale applications

Maximum lifting force for a neodymium magnet – what contributes to it?

The given pulling force of the magnet represents the maximum force, measured in the best circumstances, namely:

• using a steel plate with low carbon content, serving as a magnetic circuit closure
• having a thickness of no less than 10 millimeters
• with a polished side
• in conditions of no clearance
• under perpendicular detachment force
• in normal thermal conditions

Practical lifting capacity: influencing factors

Practical lifting force is determined by 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 was assessed with the use of a steel plate with a smooth surface of suitable thickness (min. 20 mm), under perpendicular pulling force, in contrast under attempts to slide the magnet the load capacity is reduced by as much as 5 times. Moreover, even a slight gap {between} the magnet and the plate lowers the load capacity.