Adjustments And Use; Arms And Electrodes Set Up; Electrode Force Adjustment; Welding Parameters Adjustment - TECNA 7911 Manuel D'instruction

ADJUSTMENTS AND USE

ARMS AND ELECTRODES SET UP

With electrodes A clamping the pieces, the arms C should be
parallel and the electrode tips must combine. To adjust them
slacken the locking pin (B), shift the electrode A, and block again.
If it is necessary, pull out the arms for 6 mm. maximum (Fig.6).
To disassemble and adjust the electrodes slacken locking pin B
screw on arms with electrodes Ø 12 (range 74XX).
On cooling arms, to disassemble electrodes use a key (Fig.4).
Electrode tip diameter varies according to the thickness; values
on table 2 should not be exceeded as this can cause overheating
and weak welds (Fig. 8).
When a less pronounced impression of the electrodes on the sheet
metal is required, or when it is necessary to weld plates of different
thickness, the electrodes should be set by using a fine file applying
a reduced force at the electrodes. (Fig. 7)

ELECTRODE FORCE ADJUSTMENT

Adjust the electrode force by following table 2 stating both pressure
values and arms length (the value most complete range is stated
on table 1). In order to adjust the pressure, act on the reducer as
per Picture 3.

WELDING PARAMETERS ADJUSTMENT

Table 2 shows the times and setting for various types of welding.
The timer has a compensation circuit which calculates the actual
welding time needed even when paint, rust or dirt obstruct the
passage of welding current, thus the timer only ends the cycle
when a perfect complete weld has been obtained. Welding current
time is shown on dial I.
Welding current can be adjusted from 100% to 40% by means of
knob 63. We recommend to always use the highest value except
for: very thin thickness, rods with reduced Ø (1-3 mm), stainless
steel sheets.
Another advantage offered by current adjustment is the possibility
of reducing the power absorption when this is too high for the
mains on which the welder is used (of course, you have to increase
the welding and check the welds quality).

WORK

Before connecting the unit to the power line, check if the welder
voltage corresponds to the one of your power supply, as well as
that both socket and system are in a good status, and that the
mains section is of the correct size (see table 5).
Check that the required performances are within the values stated
on table 3 and 4.
Before starting working, check that all safety warnings have been
read and understood.
When welding, the supply voltage drop must not exceed 10-15%.
When trigger 26 is pressed, the welder closes the electrodes;
when the correct force at the electrode is reached, a differential
pressure switch activates the timer which switches on the welding
current for the period selected by means of knob 66 and 63.
Release the pressure at the trigger 26 0,2"-0,8" after the welding
current has stopped; this delay improve the weld quality.
Before starting the welding process, check the welding conditions
(time, pressure, etc.). Use two off-cuts of the sheet to weld; the
spot is correct when the pulling test causes the coming out of the
welding nugget with the hole of a sheet. The twist test shows a
pure area without porosity (see fig. 9).
When the work is over, disconnect the welder from the mains
supply.
Never carry the welder by its cord or yank it to take it off from the
socket. Keep the cord away from heat, oil and sharp edges.
Art. / Item 7911-7913-7915

MAINTENANCE

The following maintenance operations must be carried out
by specialised personnel only, trained to accomplish them
under safety conditions. When possible, the welder must be
disconnected from both pneumatic and electric supply.

ORDINARY MAINTENANCE

GENERAL WARNINGS

• Always check that the screws of electrodes, electrode-holders,
arms, and arm-holders (13), as well as the rigid (91-99) and
flexible (10) connections well tightened.
• Remove oxide traces on the secondary circuit with fine sand
paper.
• Periodically oil axes 19-20-82-83.
• Keep the spot gun free from dust and metal particles attracted
by the magnetic field formed by the welder when operating.
• Neither washing the welding unit with jets of water which could
enter it, nor use strong solvents, thinner, nor benzine that could
damage either painting or the machine plastic components.
• Discharge the moisture from the pressure reduces M (Fig. 3).

ELECTRODES

Electrodes maintenance must be carried out with the welder
switched off and with the compressed air supply disconnected
• When operating, the electrodes must be kept clean and their
diameter must be kept suitable for the work to be carried out.
Too worn electrodes must be replaced.
• On water cooled arms, do not use sealing products to remove
water leakage on the electrode taper. To facilitate the electrode
removal and to prevent from both taper seizure and leakage,
use high conductivity grease similar to the standard one.

PNEUMATIC CIRCUIT

• In case of air leakage, immediately stop operating and remove
it.
• Periodically discharge the moisture from the air assembly (74)
and check that it is both clean and tightened.
• Check pressure gauge calibration.
• Check the status of both compressed air and corresponding
connections.

COOLING CIRCUIT (ON ITEMS 7913-7915 ONLY)

• Check that cooling water circulates freely and in the required
quantity and that the input temperature is included within 10
and 30°C.
• Check the status of both water hoses and corresponding
connections.
• If, during the winter terms, the welder must be stored up in
cool rooms, it is necessary to carefully drain first the cooling
circuit to prevent from possible damages caused by frozen
water.

ELECTRIC CIRCUIT

• Periodically check ground efficiency.
• Periodically check the supply cable status.
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