MW 15x4 / N38 - cylindrical magnet

Strengths and weaknesses of rare earth magnets.

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

• Their strength is maintained, and after approximately ten years it drops only by ~1% (theoretically),
• They maintain their magnetic properties even under strong external field,
• Thanks to the smooth finish, the surface of Ni-Cu-Ni, gold-plated, or silver-plated gives an visually attractive appearance,
• Magnets are characterized by impressive magnetic induction on the outer side,
• Made from properly selected components, these magnets show impressive resistance to high heat, enabling them to function (depending on their form) at temperatures up to 230°C and above...
• Thanks to the possibility of accurate shaping and customization to unique requirements, NdFeB magnets can be produced in a wide range of shapes and sizes, which expands the range of possible applications,
• Significant place in innovative solutions – they are commonly used in hard drives, electromotive mechanisms, medical equipment, also industrial machines.
• Compactness – despite small sizes they generate large force, making them ideal for precision applications

Disadvantages of NdFeB magnets:

• Susceptibility to cracking is one of their disadvantages. Upon strong impact they can fracture. We advise keeping them in a steel housing, which not only protects them against impacts but also increases their durability
• When exposed to high temperature, neodymium magnets experience a drop in force. Often, when the temperature exceeds 80°C, their strength decreases (depending on the size, as well as shape of the magnet). For those who need magnets for extreme conditions, we offer [AH] versions withstanding up to 230°C
• Magnets exposed to a humid environment can rust. Therefore while using outdoors, we suggest using water-impermeable magnets made of rubber, plastic or other material resistant to moisture
• Due to limitations in realizing nuts and complicated forms in magnets, we recommend using cover - magnetic mount.
• Health risk related to microscopic parts of magnets are risky, in case of ingestion, which gains importance in the context of child health protection. Additionally, small elements of these devices can be problematic in diagnostics medical after entering the body.
• Due to expensive raw materials, their price exceeds standard values,

Breakaway strength of the magnet in ideal conditions – what affects it?

The load parameter shown concerns the peak performance, obtained under optimal environment, specifically:

• using a sheet made of mild steel, serving as a magnetic yoke
• whose thickness is min. 10 mm
• with a surface free of scratches
• under conditions of no distance (surface-to-surface)
• for force acting at a right angle (pull-off, not shear)
• in temp. approx. 20°C

What influences lifting capacity in practice

Holding efficiency is affected by working environment parameters, mainly (from most important):

• Distance – existence of any layer (paint, tape, air) interrupts the magnetic circuit, which lowers power steeply (even by 50% at 0.5 mm).
• Load vector – maximum parameter is available only during perpendicular pulling. The force required to slide of the magnet along the plate is typically several times smaller (approx. 1/5 of the lifting capacity).
• Element thickness – for full efficiency, the steel must be adequately massive. Thin sheet limits the attraction force (the magnet "punches through" it).
• Metal type – different alloys reacts the same. Alloy additives worsen the attraction effect.
• Plate texture – ground elements guarantee perfect abutment, which improves field saturation. Rough surfaces reduce efficiency.
• Heat – neodymium magnets have a sensitivity to temperature. At higher temperatures they are weaker, and at low temperatures they can be stronger (up to a certain limit).

* Lifting capacity was measured using a polished steel plate of optimal thickness (min. 20 mm), under perpendicular detachment force, whereas under parallel forces the lifting capacity is smaller. In addition, even a minimal clearance {between} the magnet’s surface and the plate reduces the load capacity.