Special Information On Handling Switchable Permanent Magnets - ALFRA ROTABEST SP-V Mode D'emploi

Special Information on Handling Switchable Permanent Magnets

The magnetic surface of the incorporated TML permanent magnet is located on the underside of the magnetic drill
stand and generates the magnetic holding force through magnetic flux when activated. The magnet can be
activated independently of the mains voltage by pressing the lever down. For the magnet to be released the black
safety tab must be pushed by using the ball of your hand and the lever pulled upwards. The machine remains
attached to the workpiece even in the event of a power failure.
Material thickness
The magnetic flux of the TML permanent magnet requires a minimum material thickness of 8 mm to flow
completely through the workpiece. If this material thickness is not given, the maximum holding force is reduced in
accordance with the material thickness. Conventional electric or permanent magnets have a deeply penetrating
magnetic field similar to tree tap roots, and require a large material thickness of more than 25 mm to achieve the
maximum holding force. The compact magnetic field of the ALFRA TML magnets is similar to a shallow root and
achieves maximum holding force even with small material thicknesses, so that drilling can be done with sufficient
holding force even on thin sheets from only 3–4 mm thick.
Material
The load-bearing capacity of the permanent magnets is determined using an S235 material. Steels with a high
carbon content or whose structure has been changed by heat treatment have a low holding force. Foamed or pore-
flawed cast parts also have a lower holding force.
Material
Non-alloyed steel (0.1-0.3% C content)
Non-alloyed steel (0.3-0.5% C content)
Cast steel
Grey cast iron
Nickel
Stainless steel, aluminium, brass
Surface quality
If a kind of "air gap" is produced between the magnet and the workpiece, this reduces the holding force. In the
same way, paint, rust, scale, surface coatings, grease or similar substances all form an air gap between the
workpiece and the switchable magnet, reducing the holding force.
Temperature
The high-power permanent magnets installed in the TML magnet irreversibly lose their magnetic properties from a
temperature of more than 80°C, so that the full holding force is never reached again even after the magnets have
cooled down.
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Magnetic force in %
100
90-95
90
45
11
0