Mma Welding; Maintenance - Telwin TIG DC Series Bedienungsanleitung

fittings.
WARNING! Always close the gas bottle valve when the work has been
completed.
5.5.2 MMA welding
Almost all coated electrodes must be connected to the generator's positive pole (+),
except acid coated electrodes, which must to be connected to the negative pole (-).
Connecting the welding cable-electrode holder clamp
Fit a special clamp to the terminal which tightens the bare section of the electrode.
This cable must be connected to the terminal with the (+) symbol.
Connecting the return cable to the welding current
To be connected to the piece being welded or to the metal workbench on which it is
positioned, as close as possible to the joint that is being made
This cable must be connected to the terminal with the (-) symbol.
6. WELDING: PROCEDURE DESCRIPTION
6.1 TIG WELDING
6.1.1 General principles
TIG welding is a welding procedure that exploits the heat generated by the electric
arc which is struck and maintained between a non-consumable electrode (Tungsten)
and the piece to be welded. The Tungsten electrode is supported by a torch which is
able to deliver welding current and protect the electrode and the weld pool against
atmospheric oxidation using an inert gas flow (normally Argon: Ar 99.5%) supplied via
a ceramic nozzle (FIG. G).
TIG welding is suitable for all low-alloy and high-alloy carbon steels and to heavy
metals, copper, nickel, titanium and relative alloys.
Electrodes with 2% cerium content (grey coloured strip) are generally used for TIG DC
welding with a (-) pole electrode.
It is essential to sharpen the Tungsten electrode axially on a grinding wheel, see FIG.
H, making sure that the tip is perfectly concentric to prevent arc deviation. It is important
to ensure grinding is performed lengthwise along the electrode. This operation must
be repeated periodically according to the use, wear and tear of the electrode, or when
the same has been accidentally contaminated, oxidised or used incorrectly.
To achieve good welding results, it is essential to use the exact electrode diameter and
current, as indicated in the table (TAB.3).
The ceramic nozzle will normally protrude from the electrode by 2-3mm, and may
reach 8 mm for corner welding operations.
Fusion welding solders the joint edges. No welding material is required when using
specifically prepared thin diameters (up to approx. 1 mm (FIG. I).
When dealing with thicker materials, it is necessary to use suitably sized sticks made
of the same base material, and ensure the edges are prepared properly (FIG. L). To
achieve good welding results, it is important to ensure all pieces are perfectly clean,
with no sign of oxide, oil, grease, solvents etc.
6.1.2 Procedure (LIFT strike)
- Use the knob to adjust the welding current to the required rate; adjust this value
during welding processes to adapt to the actual heat transfer required.
- Check that the gas flow is correct.
The electric arc strike involves the to-and-fro stroke of the Tungsten electrode on the
piece to be welded. This strike procedure causes less electro-irradiated disturbance
and reduces Tungsten inclusions and wear of the electrode to a minimum; rest
the electrode tip on the piece using a very light amount of pressure, then raise
the electrode by 2-3 mm with a slight delay to strike the arc. At the beginning, the
welding machine delivers a I
BASE
will be delivered.
- To interrupt welding operations, quickly raise the electrode away from the piece.
6.2 MMA WELDING
6.2.1 General principles
- It is essential to follow the recommendations provided by the manufacturer on the
electrode packaging which indicates the correct electrode polarity and relative rated
current.
- Welding current is regulated to suit the diameter of the electrode being used and the
type of soldering to be performed; an example of the currents used for the various
electrode diameters can be seen below:
Ø Electrode (mm)
1.6
2
2.5
3.2
4
5
- One can see that for the same diameter electrode, high levels of current will be
used for flat welding, whilst lower current levels will be used for vertical or overhead
welding.
- The mechanical characteristics of the welded joint are determined by the intensity
of the selected current and also other welding parameters such as the length of the
arc, the operating speed and position, the diameter and quality of the electrodes
(to ensure correct conservation, use special packaging or containers to store and
protect the electrodes against humidity).
- Welding characteristics also depend on the Arc Force value (dynamic behaviour)
of the welding machine. This parameter can be set via the control panel (where
applicable), or using a 2 potentiometer remote control.
- Note that high Arc Force values provide deeper penetration and allow welding to
be performed in any position, typically using basic electrodes; low Arc Force values
provide a smoother arc without spraying, typically using rutile electrodes.
The welding machine is also fitted with Hot Start and Anti Stick devices which
guarantee easy start procedures and prevent the electrode from sticking to the
piece.
6.2.2 Procedure
- Hold the mask IN FRONT OF THE FACE, then lightly scratch the electrode tip on
the piece to be welded as if you were trying to strike a match; this is the correct way
of striking the arc: where applicable, enable the VRD device and the arc strike will be
achieved using quick to-and-fro strokes of the electrode on the piece to be welded.
WARNING: DO NOT TAP the electrode against the piece; this can damage the
coating and make it difficult to strike the arc.
- A soon as the arc is struck, try to maintain a distance from the piece which is
equivalent to the diameter of the electrode being used, and try to maintain this
distance as constant as possible during the welding operations; remember that the
angle of the electrode as it moves forwards should be about 20-30 degrees.
- At the end of the welding seam, move the electrode tip backwards slightly, above the
crater, and fill it in; now quickly lift the electrode from the weld pool to extinguish the
arc (Examples of welding seams - FIG. M).
current; after a few seconds the set welding current
Welding current (A)
Min.
25
40
60
80
120
150

7. MAINTENANCE

WARNING! BEFORE CARRYING OUT MAINTENANCE OPERATIONS
MAKE SURE THE WELDING MACHINE IS SWITCHED OFF AND DISCONNECTED
FROM THE MAIN POWER SUPPLY.
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.
- Accurately couple the electrode holder clamp, the gas diffusor calibrated with the
diameter of the selected electrode in order to prevent overheating, poor diffusion of
the gas and relative malfunctions.
- Before every use, check the state of wear and the correct assembly of the terminal
parts of the torch: nozzle, electrode, electrode holder clamp, gas diffusor.
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.).
- Check that the yellow led (ie. thermal protection interruption- either over or
undervoltage or short circuit) is not lit.
- 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 the mains voltage: if the value is too high or too low the welding machine will
be stopped.
Max. - Check that there is no short-circuit at the output of the machine: if this is the case
eliminate the incovenience.
50
- Check that all connections of the welding circuit are correct, particularly that the
80
work clamp is well attached to the workpiece, with no interferring material or
surface-coverings (ie. Paint).
110
- Protective gas must be of appropriate type (Argon 99.5%) and quantity.
160
200
250
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