UMH 25x8x45 [M5] / N38 - magnetic holder with hook

Strengths and weaknesses of neodymium magnets.

In addition to their long-term stability, neodymium magnets provide the following advantages:

• They do not lose magnetism, even over around ten years – the drop in strength is only ~1% (theoretically),
• Magnets effectively protect themselves against demagnetization caused by foreign field sources,
• A magnet with a metallic nickel surface is more attractive,
• Magnetic induction on the working layer of the magnet is extremely intense,
• Neodymium magnets are characterized by extremely high magnetic induction on the magnet surface and can function (depending on the form) even at a temperature of 230°C or more...
• Thanks to versatility in constructing and the capacity to modify to complex applications,
• Huge importance in future technologies – they are used in magnetic memories, brushless drives, diagnostic systems, as well as multitasking production systems.
• Thanks to concentrated force, small magnets offer high operating force, with minimal size,

Disadvantages of NdFeB magnets:

• They are fragile upon too strong impacts. To avoid cracks, it is worth securing magnets in a protective case. Such protection not only shields the magnet but also increases its resistance to damage
• Neodymium magnets decrease their strength under the influence of heating. As soon as 80°C is exceeded, many of them start losing their power. Therefore, we recommend our special magnets marked [AH], which maintain durability even at temperatures up to 230°C
• Due to the susceptibility of magnets to corrosion in a humid environment, we recommend using waterproof magnets made of rubber, plastic or other material resistant to moisture, when using outdoors
• We suggest casing - magnetic mechanism, due to difficulties in producing nuts inside the magnet and complex forms.
• Potential hazard to health – tiny shards of magnets pose a threat, if swallowed, which becomes key in the aspect of protecting the youngest. Furthermore, tiny parts of these magnets are able to disrupt the diagnostic process medical when they are in the body.
• High unit price – neodymium magnets have a higher price than other types of magnets (e.g. ferrite), which can limit application in large quantities

Best holding force of the magnet in ideal parameters – what affects it?

The force parameter is a theoretical maximum value conducted under specific, ideal conditions:

• using a base made of high-permeability steel, acting as a ideal flux conductor
• possessing a thickness of minimum 10 mm to ensure full flux closure
• characterized by smoothness
• under conditions of ideal adhesion (metal-to-metal)
• for force acting at a right angle (pull-off, not shear)
• at standard ambient temperature

Magnet lifting force in use – key factors

During everyday use, the actual holding force is determined by several key aspects, ranked from crucial:

• Clearance – existence of foreign body (rust, tape, gap) acts as an insulator, which reduces capacity steeply (even by 50% at 0.5 mm).
• Loading method – declared lifting capacity refers to detachment vertically. When attempting to slide, the magnet holds significantly lower power (often approx. 20-30% of maximum force).
• Base massiveness – insufficiently thick plate causes magnetic saturation, causing part of the flux to be lost into the air.
• Steel grade – the best choice is pure iron steel. Cast iron may generate lower lifting capacity.
• Smoothness – full contact is obtained only on smooth steel. Rough texture reduce the real contact area, reducing force.
• Thermal conditions – neodymium magnets have a negative temperature coefficient. At higher temperatures they lose power, and in frost they can be stronger (up to a certain limit).

* Lifting capacity was determined using a polished steel plate of suitable thickness (min. 20 mm), under perpendicular pulling force, in contrast under shearing force the holding force is lower. In addition, even a small distance {between} the magnet’s surface and the plate decreases the lifting capacity.