Telwin TIG DC Series Bedienungsanleitung Seite 8

copper, nickel, titanium and their alloys.
For TIG DC welding with the electrode to the (-) terminal the electrode with 2% thorium
(red band) is usually used or else the electrode with 2% cerium (grey band).
It is necessary to sharpen the tungsten electrode axially on the grinding wheel,
as shown in FIG. M, making sure that the tip is perfectly concentric to prevent arc
deviation. It is important to carry out the grinding along the length of the electrode.
This operation should be repeated periodically, depending on the amount of use and
wear of the electrode, or when the electrode has been accidentally contaminated,
oxidised or used incorrectly. In TIG DC mode 2-stroke (2T) and 4-stroke(4T) operation
are possible.
6.1.3 TIG AC welding
This type of welding can be used to weld metals such as aluminium and magnesium,
which form a protective, insulating oxide on their surface. By reversing the welding
current polarity it is possible to "break" the surface layer of oxide by means of a
mechanism called "ionic sandblasting". The voltage on the tungsten electrode
alternates between positive (EP) and negative (EN). During the EP period the oxide
is removed from the surface ("cleaning"or "pickling") allowing formation of the pool.
During the EN period there is maximum heat transfer to the piece, allowing welding.
max=250A: The possibility of varying the balance parameter in AC
Model with I
2
means that it is possible to reduce the EP current period to a minimum, allowing
quicker welding.
Higher balance values give quicker welding, greater penetration, a more concentrated
arc, a narrower weld pool and limited heating of the electrode. Lower values give a
cleaner piece. If the balance value is too low this will widen the arc and the de-oxidised
part, overheat the electrode with consequent formation of a sphere on the tip making it
more difficult to strike the arc and control its direction. If the balance value is too high
this will create a "dirty" weld pool with dark inclusions.
The table (TAB. 5) summarises the effects of parameter changes in AC welding.
In TIG AC mode 2-stroke (2T) and 4-stroke (4T) operation are possible.
The instructions for this welding procedure are also valid.
The table (TAB. 4) shows suggested values for welding on aluminium; the most
suitable electrode is a pure tungsten electrode (green band).
6.1.4 Procedure
- Use the knob to adjust the welding current to the desired value; if necessary adjust
during welding to the actual required heat transfer.
- Press the torch pushbutton and make sure that the correct amount of gas exits from
the torch; if necessary set the PRE GAS (only model with I
GAS times. These times should be adjusted according to the operation conditions:
in particular the gas delay must allow the electrode and bath to cool after welding
without coming into contact with the atmosphere (oxidation and contamination).
TIG mode with 2T sequence:
- Press the torch pushbutton (P.T.) down fully, strike the arc and keep it at a distance
of 2-3mm from the piece.
- To interrupt welding release the torch pushbutton, which gradually stops the current
(if the FINAL RAMP function is active only model with I
extinguishes the arc with subsequent post gas.
TIG mode with 4T sequence (Model with I
- When the pushbutton is pressed the first time the arc ignites at the welding current.
This value is maintained even when the pushbutton is released. Pressing the
pushbutton and releasing it again ends the welding cycle, starting the POST GAS
period.
TIG mode with 4T sequence (Model with I
- When the pushbutton is pressed the first time the arc ignites at the I Start current.
When released, the current rises to the value of the welding current; this value is
maintained even when the pushbutton is released. When the pushbutton is pressed
again, the current decreases to I minimum , as set in the FINAL RAMP function. This
value is maintained until the pushbutton is released, stopping the welding cycle
and starting the POST GAS period. If the pushbutton is released during the FINAL
RAMP function, the welding cycle stops immediately and the POST GAS period
begins.
6.2 MMA WELDING
- It is most important that the user refers to the maker's instructions indicated on the
stick electrode packaging. This will indicate the correct polarity of the stick electrode
and the most suitable current.
- The welding current must be regulated according to the diameter of the electrode in
use and the type of the joint to be carried out: see below the currents corresponding
to various electrode diameters:
Ø Electrode (mm)
1.6
2
2.5
3.2
4
5
- The user must consider that, according to the electrode diameter, higher current
values must be used for flat welding, whereas for vertical or overhead welds lower
current values are necessary.
- As well as being determined by the chosen current intensity, the mechanical
characteristics of the welded join are also determined by the other welding
parameters i.e. arc length, working rate and position, electrode diameter and
quality (to store the electrodes correctly, keep them in a dry place protected by their
packaging or containers).
6.2.1 Procedure
- Holding the mask IN FRONT OF THE FACE, strike the electrode tip on the workpiece
as if you were striking a match. This is the correct strike-up method.
WARNING: do not hit the electrode on the workpiece, this could damage the
electrode and make strike-up difficult.
- As soon as arc is ignited, try to maintain a distance from the workpiece equal to the
diameter of the electrode in use. Keep this distance as much constant as possible
for the duration of the weld. Remember that the angle of the electrode as it advances
should be of 20-30 grades.
- At the end of the weld bead, bring the end of the electrode backward, in order to
fill the weld crater, quickly lift the electrode from the weld pool to extinguish the arc
(CHARACTERISTICS OF THE WELD BEAD - FIG. N).
7. MAINTENANCE
WARNING! BEFORE CARRYING OUT MAINTENANCE OPERATIONS
MAKE SURE THE WELDING MACHINE IS SWITCHED OFF AND DISCONNECTED
FROM THE MAIN POWER SUPPLY.
max=250A) and POST
2
max=250A) or immediately
2
max=180A):
2
max=250A):
2
Welding current (A)
min. max.
25 - 50
40 - 80
60 - 110
80 - 160
120 - 200
150 - 250
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.
- Connect the electrode holder clamp and the calibrated gas diffusor accurately,
according to the diameter of the selected electrode to avoid overheating, bad gas
diffusion and relative bad operation.
- Before use, always make sure that the end parts of the torch (nozzle, electrode,
electrode holding clamp, gas diffusor) are assembled correctly and not worn.
7.2 EXTRAORDINARY MAINTENANCE
EXTRAORDINARY MAINTENANCE MUST ONLY BE CARRIED OUT BY
TECHNICIANS WHO ARE EXPERT OR QUALIFIED IN THE ELECTRIC-
MECHANICAL FIELD, AND IN FULL RESPECT OF THE IEC/EN 60974-4
TECHNICAL DIRECTIVE.
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.
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.
- Periodically, and in any case with a frequency in keeping with the utilisation and with
the environment's dust conditions, inspect the inside of the welding machine and
remove the dust deposited on the electronic boards with a very soft brush or with
appropriate 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.
- After having carried out maintenance or repairs, restore the connections and wiring
as they were before, making sure they do not come into contact with moving parts or
parts that can reach high temperatures. Tie all the wires as they were before, being
careful to keep the high voltage connections of the primary transformer separate
from the low voltage ones of the secondary transformer.
Use all the original washers and screws when closing the casing.
8. TROUBLESHOOTING
IN CASE OF UNSATISFACTORY FUNCTIONING, BEFORE SERVICING MACHINE
OR REQUESTING ASSISTANCE, CARRY OUT THE FOLLOWING CHECK:
- Check that the welding current is correct for the diamter and electrode type in use.
- Check that when general switch is ON the relative lamp is ON. If this is not the case
then the problem is located on the mains (cables, plugs, outlets, fuses, etc.).
- The yellow LED signalling that the thermostatic safeguard has cut in is not
illuminated.
- Check that the nominal intermittance ratio is correct. In case there is a thermal
protection interruption, wait for the machine to cool down, check that the fan is
working properly.
- Check that all connections of the welding circuit are correct, particularly that the
work clamp is well attached to the workpiece, with no interferring material or
surface-coverings (ie. Paint).
- Protective gas must be of appropriate type (Argon 99.5%) and quantity.
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