ALFRA ROTABEST RB 35 SP Manual De Instrucciones página 20

SPEciAL inFORMATiOn On hAndLing SwiTchABLE PERMAnEnT MAgnETS
The magnetic surface is located on the underside of the magnetic core drilling machine 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 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 work piece, 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 work piece and the switchable magnet, reducing the holding force.
Temperature
The high-power permanent magnets installed in the 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.
20
Magnetic force in %
100
90-95
90
45
11
0