CM PML-3 / N45 - magnetic gripper

Advantages as well as disadvantages of neodymium magnets NdFeB.

In addition to their immense field intensity, neodymium magnets offer the following advantages:

• They retain their full power for nearly ten years – the drop is just ~1% (in theory),
• They are very resistant to demagnetization caused by external magnetic sources,
• Thanks to the polished finish and silver coating, they have an visually attractive appearance,
• They have exceptional magnetic induction on the surface of the magnet,
• These magnets tolerate elevated temperatures, often exceeding 230°C, when properly designed (in relation to form),
• The ability for precise shaping as well as adaptation to custom needs – neodymium magnets can be manufactured in a wide range of shapes and sizes, which amplifies their functionality across industries,
• Important function in new technology industries – they find application in data storage devices, rotating machines, diagnostic apparatus or even technologically developed systems,
• Relatively small size with high magnetic force – neodymium magnets offer impressive pulling strength in compact dimensions, which makes them ideal in compact constructions

Disadvantages of NdFeB magnets:

• They are prone to breaking when subjected to a sudden impact. If the magnets are exposed to physical collisions, we recommend in a metal holder. The steel housing, in the form of a holder, protects the magnet from breakage and additionally strengthens its overall robustness,
• They lose field intensity at elevated 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,
• Magnets exposed to damp air can corrode. Therefore, for outdoor applications, we suggest waterproof types made of coated materials,
• Using a cover – such as a magnetic holder – is advised due to the restrictions in manufacturing threads directly in the magnet,
• Potential hazard related to magnet particles may arise, in case of ingestion, which is important in the family environments. Additionally, tiny components from these products might disrupt scanning if inside the body,
• Due to the price of neodymium, their cost is considerably higher,

Maximum magnetic pulling force – what it depends on?

The given holding capacity of the magnet corresponds to the highest holding force, measured under optimal 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 polished side
• in conditions of no clearance
• in a perpendicular direction of force
• in normal thermal conditions

Practical aspects of lifting capacity – factors

The lifting capacity of a magnet is influenced by in practice key elements, from primary to secondary:

• 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.

* Holding force was measured on a smooth steel plate of 20 mm thickness, when a perpendicular force was applied, however under attempts to slide the magnet the load capacity is reduced by as much as fivefold. In addition, even a minimal clearance {between} the magnet’s surface and the plate lowers the holding force.