Welding: Description Of The Procedure - Telwin MASTERMIG 300 Manuel D'instructions

the tab for pulling the spindle is correctly seated in its hole (1a).
- Release the pressure counter-roller/s and move it/them away from the lower roller/s
(2a).
- Make sure the puller roller is suitable for the wire being used (2b).
- Free the end of the wire and remove the distorted end with a clean cut and no burr;
turn the reel anti-clockwise and thread the end of the wire into the wire-guide infeed,
pushing it 50-100mm into the wire guide of the torch fitting (2c).
- Re-position the counter-roller/s, adjusting the pressure to an intermediate value, and
make sure that the wire is correctly positioned in the groove of the lower roller (3).
- Use the adjustment screw located at the centre of the spindle to apply a slight braking
pressure on the spindle itself (1b).
- Remove the nozzle and contact tip (4a).
- Insert the welding machine plug in the power supply outlet, switch on the welding
machine, press the torch button and wait for the end of the wire to pass through the
whole of the wire guide hose and protrude by 10-15 cm from the front part of the
torch, release the button.
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WARNING! During these operations the wire is live and subject to mechanical
stress; therefore if adequate precautions are not taken the wire could cause
hazardous electric shock, injury and striking of electric arcs:
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- Do not direct the mouthpiece of the torch towards parts of the body.
- Keep the torch away from the gas bottle.
- Re-fit the contact tip and the nozzle onto the torch (4b).
- Check that wire feed is regular; set the roller and spindle braking pressure to the
minimum possible values making sure that the wire does not slide in the groove and
when feed is halted the loops of wire are not loosened by excessive reel inertia.
- Cut the end of the wire so that 10-15 mm protrude from the nozzle.
- Close the reel compartment door.

6. WELDING: DESCRIPTION OF THE PROCEDURE

6.1 PRELIMINARY OPERATIONS
- Insert the earth connector into the (-) socket (for welding machines with a single earth
connector).
- Insert the earth connector in the desired (-) quick connector depending on the
material to be welded (for welding machines with 2 or more earth connectors);
- quick connector (-) with max reactance (
material and resulting (Al) alloys, copper alloys (CuAl/CuSi).
- quick connector (-) with min reactance (
(SS), carbon steel and low-alloy (Fe) steel.
- Connect the return cable to the piece being welded.
- Turn on and adjust the protective gas using the pressure reducing valve (5-7 l/min)
NOTE: At the end of the job, remember to turn off the protective gas.
- Switch the welder on and set the welding current by means of the rotary switch.
6.2 WELDING (FIG. H)
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.
6.3 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. To 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 Teflon guide hose.
The above pieces for aluminium welding are available as optionals.
6.4 SPOT WELDING (FIG.I)
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.
6.5 RIVET WELDING (FIG.L)
This operation is only possible for compact welding machines with an/one earth
connector.
This process allows dented or deformed metal sheets to be re-shaped, without having
) or position 2-3 for aluminium
) or position 1-2 for stainless steel
FIG. G
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 latter to the metal sheet. The dented metal sheet can now be
re-shaped using the appropriate appliance
6.6 METAL SHEET HARDENING (FIG.M)
This operation is only possible for compact welding machines with one or more earth
connectors.
In order to carry out this process, the kit should be requested.
After welding and hammering, the metal sheet looses its original characteristics; body
work-shops normally use oxyacetylene welding torches to return the metal sheet to its
original state. This torch is used to heat the metal sheet up to about 800° Celsius and is
then rapidly cooled using a cloth soaked with water.
The oxyacetylene equipment can now be replaced using the following hardening
process:
- Remove the torch nozzle and fit the special electrode holder and the coal electrode by
tightening the appropriate knob.
- Turn the adjustment switch to position 1 (higher positions may overheat the electrode
and the machine).
- Release the pressure from the towing rollers by releasing the spring in order to
prevent the wire from being dragged along the torch.
If only a small area is to be hardened, carry out the operation as if it were spot welding by
placing the end of the electrode in contact with the metal sheet until this heats up. When
the sheet is sufficiently heated, cool it down using a cloth soaked with water. If a large
area is to be hardened, the electrode should be rotated.
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WARNING:
- The indicator light comes on when there is overheating and cuts off the power supply;
it will reset automatically within a few minutes, after cooling down.
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7. MAINTENANCE
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WARNING! BEFORE CARRYING OUT MAINTENANCE OPERATIONS MAKE
SURE THE WELDING MACHINE IS SWITCHED OFF AND DISCONNECTED FROM
THE MAIN POWER SUPPLY.
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7.1 ROUTINE MAINTENANCE:
ROUTINE MAINTENANCE OPERATIONS CAN BE CARRIED OUT BY THE
OPERATOR.
7.1.1 Torch
- Do not put the torch or its cable on hot pieces; this would cause the insulating
materials to melt, making the torch unusable after a very short time;
- Make regular checks on the gas pipe and connector seals;
- Every time the wire reel is changed, blow out the wire-guide hose using dry
compressed air (max. 5 bar) to make sure it is not damaged;
- Before using the welding machine, always check the torch terminal parts for wear
and make sure they are assembled correctly: nozzle, contact pipe, gas diffuser.
7.1.2 Wire feeder
- Make frequent checks on the state of wear of the wire feeder rollers, regularly remove
the metal dust deposited in the feeder area (rollers and wire-guide infeed and
outfeed).
7.2 EXTRAORDINARY MAINTENANCE
EXTRAORDINARY MAINTENANCE OPERATIONS SHOULD BE CARRIED OUT
ONLY AND EXCLUSIVELY BY SKILLED OR AUTHORISED ELECTRICAL-
MECHANICAL TECHNICIANS.
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WARNING! BEFORE REMOVING THE WELDING MACHINE PANELS AND
WORKING INSIDE THE MACHINE MAKE SURE THE WELDING MACHINE IS
SWITCHED OFF AND DISCONNECTED FROM THE MAIN POWER SUPPLY
OUTLET.
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If checks are made inside the welding machine while it is live, this may cause
serious electric shock due to direct contact with live parts and/or injury due to
direct contact with moving parts.
- Inspect the welding machine regularly, with a frequency depending on use and the
dustiness of the environment, and remove the dust deposited on the transformer,
reactance and rectifier using a jet of dry compressed air (max. 10 bar).
- Do not direct the jet of compressed air on the electronic boards; these can be cleaned
with a very soft brush or suitable solvents.
- At the same time make sure the electrical connections are tight and check the wiring
for damage to the insulation.
- At the end of these operations re-assemble the panels of the welding machine and
screw the fastening screws right down.
- Never, ever carry out welding operations while the welding machine is open.
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