IBS Magnet - Information on Holding Magnets

Know-how

All holding magnet systems are combinations of permanent magnets and iron structures. The iron on the magnet´s pole shaped into sleeves, pots or other pole pieces guides and concentrates the magnetic flux onto the holding surface.

This surface must be sufficiently large to be able to carry the total flux of the magnet. The best holding forces are obtained by using annealed steel
(St 37 K) with a flat, smooth surface.

Several magnet systems are shown below. The holding force of the system shown in comparison to an open magnet is given as an approximate factor.

1.1	"Open" disc or rod magnet Factor 1

1.2	With iron backing plate Factor 1.3

1.3	With iron backing plate plus central pole Factor 4.5

1.4	Disc magnet in iron pot (disc-type holding magnet) Factor 6

1.5	Ring magnet in iron pot with additional central pole. Factor 6

1.6	AINiCo rod magnet in iron sleeve (Deep pot holding magnet, pot magnets) Factor 7.5

1.7	U-shaped magnetic rail Factor 5.5

1.8	Magnet block between 2 flat iron strips (sandwich system) Factor 18

1.9	Battery of sandwich systems (Types L50 . . . L200) Factor 18 x number of systems

2.	Two magnet blocks with opposing poles on iron backing plate, for achieving a wide-reaching, concentrated magnetic field, as required for catching magnets.

3.	Multiple pole magnetisation on the holding surface of magnetic foils and strips enables a high density of flux lines over the magnetic surface. This magnetisation is particularly suitable for application to thin iron sheets.

4.	The holding force depends on the smoothness of the surface = remaining holding force

5.	The holding force depends on the material of the holding surface.

6.	Ratio of shifting force to holding force.

7.	A "magnetic" short-circuit is caused when both poles are bridged by iron. Connections should therefore be made from unmagnetised materials, e.g. brass, stainless steel.