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Your guide to making the best decision when choosing a magnet for holding applications

Two magnets attract to each other because their fields interact. A permanent magnet is attracted to a ferrous workpiece because magnetism is induced in the workpiece. Therefore, the permanent magnet’s field and the newly induced field in the ferrous part interact and attract.

The strength of the magnetic field represented by Br produced by a magnet and defined as flux density is measured in gauss or Tesla. The higher the Br the more powerful the magnet. Ceramic, also known as ferrite magnets, have a maximum Br of 4,000 gauss and Neo (NdFeB) magnets which are the most powerful magnets available, start at a Br of 12,500 gauss.

Holding force is proportional to Br squared. With Neodymium at about Br of 12,500 gauss and ceramic at about Br of 4,000 gauss, there will be a 9.8 times increase in holding force from ceramic to Neodymium.

For any magnet consideration the maximum attraction is magnet to magnet which will give you a specific pull force or holding force. This same force can be duplicated with one magnet paired and aligned with a steel workpiece with zero air gap. The workpiece must be equal to or larger than the surface area of the magnet and the thickness of the steel designed to get the same output. These parameters are used for applications with precise application requirements.

The choice of the type and size of magnet can be optimized for both performance cost purposes. For any general holding application, the pull force is not that precise. Depending on the ferrous material, size, thickness, alignment, air gap and grade of magnet you can get a range of results. The magnets will always attract but the strength of the magnetic field will determine how the two will interact.

The higher the magnetic field the better alignment and resultant holding force. In other words, the higher the flux density of the magnet the more aggressive the interaction and attraction to the ferrous material.

Ceramic magnets which have a limited Br of 4,000 gauss are considerably lower cost than Rare Earth (RE) magnets such as NdFeB. However, to realize the same performance level, the size of the NdFeB maybe only a quarter of the size of the ceramic one. When a performance exceeding a Br of 4,000.

For more information about magnetic assemblies, contact the experts here at TyTek for attractive answers.


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