Telwin MAXIMA 270 Manuel D'instructions page 9

SETTING THICKNESS
The setting of the thickness is carried out by adjusting the knob (Fig. C-3).
This knob regulates the welding power according to sheet thickness and
affects simultaneously the wire feeder speed as well as the amount of
current transferred to the filler wire.
Referring to the table provided in the machine (Fig. F), set the knob (Fig.
C-3) depending on the material, wire, gas, and thickness that will be
welded.
MANUAL OPERATION:
In manual mode, the wire feeding speed and the welding voltage are
adjusted separately. The knob (Fig. C-6) adjusts the wire speed, the knob
(Fig. C-7) adjusts the welding voltage (which determines the welding
power and influences the seam shape).
With reference to the table available on the machine (Fig. F) set
the knobs (Fig. C-6 and C-7) according to the material, wire, gas and
thickness you intend welding.
7. TIG DC WELDING: DESCRIPTION OF THE PROCEDURE (multiprocess
version only)
GENERAL PRINCIPLES
TIG DC welding is suitable for all types of low-alloy and high carbon
steel, and heavy metals such as copper, nickel, titanium and their alloys
(Fig. H). An electrode with 2% Cerium (grey band) is normally used for
TIG DC welding with electrode at the (-) pole. The tungsten electrode
must be axially sharpened using a grinding wheel, see Fig. I; make sure
the tip is perfectly concentric to prevent arc deviation. The electrode
must be ground along its length. This operation must be repeated
periodically according to the use and wear state of the electrode, or
when the electrode itself has been accidentally contaminated, oxidised
or used incorrectly. For the welding to be good, the exact diameter of
the electrode must be used with the exact current, see table (TAB. 5). The
electrode normally projects from the ceramic nozzle by 2-3 mm, but can
reach 8 mm for welding edges.
The weld is created by the edges that melt. Filler metal is not needed
when welding suitably prepared thin material (up to about 1 mm) (Fig.
L). A greater thickness requires rods made from the same material as the
basic material and with a suitable diameter, with edges that have been
suitably prepared (Fig. M). For welding to be successful, the pieces must
be carefully cleaned and free from oxide, grease, oil, solvent, etc.
PROCEDURE (LIFT STRIKE)
- Adjust the welding current to the desired value using knob C-3 or C-6;
Adapt the current during welding to the real thermal load necessary.
- Make sure the gas is flowing correctly.
The arc ignites through contact, distancing the tungsten electrode
from the workpiece. Igniting in this manner causes less electric-
irradiated disturbances and reduces tungsten inclusions and electrode
wear to a minimum.
- Place the tip of the electrode on the workpiece, pressing gently.
- Immediately lift the electrode by 2÷3 mm to obtain the arc strike.
The welding machine initially supplies reduced current. After a few
seconds, the set welding current is issued.
- Quickly lift the electrode from the workpiece to interrupt welding.
8. MMA WELDING: DESCRIPTION OF THE PROCEDURE (multiprocess
version only)
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
2.0
2.5
3.2
4.0
- 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
Welding current (A)
Min. Max.
25 50
40 80
60 110
80 150
120 180
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).
WARNING:
Instability of the arc due to the composition of the electrode can occur,
depending on the brand, type and thickness of the electrode coatings.
PROCEDURE
- Keeping the mask IN FRONT OF YOUR FACE, rub the tip of the electrode
on the piece to be welded, moving as if striking a match; this is the most
correct method for igniting the arc.
WARNING: DO NOT TAP the electrode against the workpiece, which
could damage the coating and make arc striking difficult.
- As soon as the arc has struck, try to keep the electrode at a distance
from the workpiece that is equivalent to the diameter of the electrode
being used, and keep this distance as constant as possible while
welding; remember that the electrode angle while moving forward
must be approx. 20-30 degrees.
- At the end of the welding seam, take the electrode end slightly back
as to the forward direction, above the crater to fill it, then quickly lift
the electrode from the weld pool to switch off the arc (Aspects of the
welding seam - Fig. N).
9. MAINTENANCE
WARNING! BEFORE
OPERATIONS MAKE SURE THE WELDING MACHINE IS
SWITCHED OFF AND DISCONNECTED FROM THE MAIN POWER
SUPPLY.
ROUTINE MAINTENANCE:
ROUTINE MAINTENANCE OPERATIONS CAN BE CARRIED OUT BY THE
OPERATOR.
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 every use, check the wear and correct assembly of the parts at
the end of the torch: nozzle, contact tip, gas diffuser.
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).
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.
- 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.
- After having carried out maintenance or repairs, restore the connections
- 9 -
CARRYING OUT MAINTENANCE