ALFRA ROTABEST RB 35 SP Manuel D'utilisation page 20

Special information on handling switchable permanent magnets
The magnetic surface is located on the underside of the magnetic core drilling machine and generate the magnetic
holding force through magnetic flow 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 in 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 flow of the TML permanent magnet requires a minimum material thickness of approx. 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 workpiece, this reduces the holding force. In the
same way, paint, rust, scale, surface coatings, grease or similar substances all form a gap, or an air gap, between
the workpiece 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.
Maintenance and inspection of the magnetic core drilling machine
The user is obliged to maintain and service the core drilling machine in compliance with the specifications in the
operating manual and according to the country-specific standards and regulations.
The maintenance intervals are classified according to the frequency with which the maintenance should be carried
out.
Always disconnect the machine from the mains before any maintenance operations, otherwise
there is a risk of injury due to unintentional machine switch-on.
Before every use...
inspect the core drilling machine and underside of the magnet for visible signs of damage
•
clean the surface of the workpiece and the underside of the magnet
•
check the blocking function of the safety tab on the lever
•
check the correct, firm fit of the core drill
•
check connection cables for damage
•
Magnetic force in %
100
90-95
90
45
11
0
20