Aluminium Welding - Telwin MASTERMIG 270/2 Manual De Instrucciones

medium-sized gas cylinder should be placed on the rear
support. Secure the gas cylinder by fastening chain, with
which it is wound, tightly to the hooks. Do not transport the
welder with large gas cylinders. Remove the cap from the
cylinder, clean the thread of the connection and open the
valve for a few seconds to let some of the gas escape. This
will prevent impurities from entering into the pressure
regulator and damaging it. Check that the connection of the
pressure regulator is fitted with a gasket and tighten it
securely. Connect the gas hose by tightening the metal hose
clamp well. Make sure that when the cylinder valve is open,
there are no gas leaks. The valve must be kept closed when
not using the welder to avoid wasting gas.
WIRE REEL ATTACHMENT (FIG. D-E )
- Open the side panel of the generator and remove the
locking screw and fit the wire reel onto the spindle so that
the end of the wire is facing upwards. Make sure that none
of the loops of wire on the reel are overlapping and that
the wire unwinds smoothly. Then re-tighten the screw.
- Make sure that the towing roller is suited to the wire used.
To replace this, simply remove the locking handwheel.
- Take the end of the wire and cut it, rounding off the point,
and thread it through the two wire guides; the wire should
not be bent and should be guided for a few centimetres,
making sure that it runs without implanting itself in the
guide hose of the torch.
- Make sure that the groove of the rollers is in line with the
wire guides.
- Adjust the lever of the pressure spring in order to provide
the towing rollers with sufficient pressure. Depending on
the wire used, the lever should be tightened accordingly;
excessive pressure could twist the wire and make wire
feeding irregular and if there is insufficient pressure, the
wire tends to slide on the roller.
- Adjust the brake with the knob on the spindle in order to
reduce the inertia of the wire reel without overloading the
towing-motor.
- Let the wire run for the whole length of the torch, turn the
main switch to position "l" and press the button of the
torch. T o prevent the wire from implanting itself into the
end of the torch, in the position where the contact tip is
located, the tip should be removed.
WELDING (FIG. F )
Once the machine has been prepared for welding by
carrying out the operations described above, simply place
the earth clamp in contact with the workpiece and press the
torch button, keeping the torch at a safe distance from the
workpiece.
Before carrying out difficult sections of welding, tests
should be carried out on scrap pieces. These tests should
be carried out using the adjustment knob in order to obtain
the best welding possible. If the arc melts in drops and
tends to go out, the speed of the wire should be increased
or the welding current decreased. If, however, the wire hits
the piece violently and causes material to be projected, the
wire speed should be reduced.
It should be remembered that in order to obtain the best
results, each type of wire is suited to a specific current and
wire feed speed. Therefore, for difficult sections of welding
and welding which requires a great deal of time, wires with
different diameters should be tried so that the most suitable
may be chosen.

ALUMINIUM WELDING

For aluminium welding, pure ARGON or an ARGON-
HELIUM mixture should be used for shielding. The wire
used should have the same characteristics as the material
to be welded. Always use an alloy wire (e.g.
aluminium/silicium); never use pure aluminium wire.
Aluminium MIG welding does not present any particular
problems. The only difficulty is in the pulling of the wire for
the whole length of the torch, since aluminium is known to
have poor mechanical characteristics. The smaller the
diameter of the wire the more this problem is accentuated.
This problem can be avoided by making the following
changes:
1.- Replace the guide hose of the torch with a Teflon guide
hose. T o withdraw this, simply loosen the screws at the
end of the torch.
2.- Use contact tips for aluminium.
3.- Replace the wire pulling rollers with those made for
aluminium
4.- Replace the steel guide hose for wire feed with a T eflon
guide hose.
The above pieces for aluminium welding are available as
optionals.
SPOT WELDING (FIG. G)
Two overlapping metal sheets can be spot-welded together
using a wire system and weld material.
This model has been specifically designed for the purposes
of spot-welding and is equipped with adjustable timer
which allows ideal spot-welding time to be set and therefore
the creation of spot-welds which have the same
characteristics.
In order to use the machine for spot-welding, it should be
set-up as follows:
- Replace the nozzle of the torch with the nozzle required
for spot-welding, which is supplied as an accessory. This
nozzle is cylindrical-shaped and has holes for gas
escape at the end
- Turn the current adjustment switch to <maximum>
position.
- Set the wire feed speed at almost maximum speed.
- Turn the switch to <TIMER> position
- Set the spot welding time according to the thickness of
the metal sheets.
To carry out the spot welding, rest the nozzle of the torch on
the surface of the first metal sheet, then press the torch
button in order to start welding: the wire will melt the first
sheet, pass through this sheet and into the second, making
a molten wedge between the two metal sheets.
The button should be pressed until the timer interrupts the
welding.
This system allows spot-welding to be carried out which
would not normally be possible with conventional spot-
welders, since metal sheets can be joined which do not
allow access to the rear side such as box-type sheets.
This system also makes the operator's work much easier
thanks to the extremely light-weight torch.
The application limits of this system depend on the width of
the first metal sheet; the second sheet may be extremely
thick.
RIVET WELDING (FIG.H)
This process allows dented or deformed metal sheets to be
re-shaped, without having to hammer out the sheets from
behind. This is particularly useful for sections of bodywork
with inaccessible rear sides.
The operation is carried out as follows:
- Replace the nozzle of the torch with the nozzle required
for riveting. This nozzle has a side hole for housing the
rivet.
- Turn the current adjustment switch to position 3.
- Adjust the feed speed according to the current and the
diameter of the wire used as if a welding operation was to
be carried out.
- Turn the switch to <TIMER> position.
- Set the time at 1-1.5 seconds
A spot of welding will therefore be carried out at the point
where the head of the rivet is located and so joining the
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