Torch Maintenance - Elettro PLASMA 74 Manual De Instrucciones

possible, close to the cutting area so as to switch the unit off
quickly if necessary. The capacity of magnetothermic switch or of
fuses in series to the switch should be equal or above the current
I absorbed by the unit. The absorbed current I
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the technical specifications on the unit close to input voltage U
available. Any extensions should have adequate sections for
absorbed current I .
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3.3 USE
Switch the unit on by turning knob A (pict.1 - 1a) of the mains
switch; this is shown by light B (pict.1 - 1a) which is on. By
pressing for a second the torch button, the compressed air flow
is opened. Check that, under this condition, the pressure shown
on gauge I (pict. 2) is about 75 PSI (4,7 bar or KPaX100),
otherwise adjust it by the knob of the reducing unit H (pict. 2),
then lock this knob by pressing it down. Connect work clamp to
the piece to be cut. Set the cutting current by means of the knob
C (pict. 1a), only for item 424. Use the Ø 1 mm nozzle up to 50A
and the Ø 1,2 mm nozzle up to 70A.
N.B. Cut quality is greatly improved if the nozzle is kept at a
distance of approx. 2 mm from the workpiece. Often for
practical reasons, however, cutting is performed with the
nozzle in contact with the workpiece. Cutting with the
nozzle in contact with the workpiece must not be performed
at currents above 50A as this leads to rapid (sometimes
even instantaneous) destruction of the nozzle hole; this in
turn leads to poor cutting quality.
Clean the work piece to ensure good electrical contact of the
work clamp. Do not connect work clamp to the piece to be
removed. Press torch button to start pilot arc, if cutting does not
start after 4 seconds, the pilot arc turns off and the button should
be pressed again to repeat the operation. When possible, the
torch should be pulled. Pulling is easier than pushing. Keep torch
in vertical position when cutting. Once cutting is over and after
releasing button, air continues to flow out of the torch for about 1
minute so it enables torch to cool down. It is recommended not
to turn the unit off before that time. If you have do drill holes or to
start the cut of the piece from its centre, you should tilt the torch
and then slowly straighten it to prevent molten metal from being
spread on nozzle (see pict. 4). This operation should be carried
out when cutting pieces of thickness above 1/8" (3 mm). If you
have to cut near angles or recesses (see picture 5) it is
recommended to use extended electrodes and nozzles. Should
circular cut be done it is recommended to use caliper (supplied
on request).
N.B. : Avoid keeping pilot arc uselessly on in air, to avoid
electrode, diffuser and nozzle consumption.
3.4 CUTTING TROUBLE
1) Insufficient penetration
This may be due to:
- high speed. Always make sure that arc thoroughly passes
through the piece to be cut and that it is not tilted, when going
forward, by a percentage above 10 ÷ 15° (see picture 6). It is
thus avoided to wear nozzle (see pict. 7) out and to burn the
nozzle holder (see picture 8).
- Excessive thickness of piece (see graph of cutting speed and
thickness).
- Work clamp not properly in electric contact with piece.
- Worn nozzle and electrode.
- Too low cutting current.
N.B. : When the unit does not thoroughly pass through, scums
clog nozzle.
2) Cutting arc switches off
This may be due to:
- worn nozzle, electrode or diffuser.
is indicated in - too high air pressure.
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- too low feed voltage.
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3) Tilted cutting
When cutting is tilted (see picture 9) switch the unit off, loosen
nozzle holder and turn nozzle by a quarter turn, then lock and try
again.
Repeat until cutting is straight (see picture 10).
4) Excessive wear of consumable parts
This may be due to:
a) too low air pressure with respect to the recommended one.
b) excessive burns on the end part of nozzle holder.
3.5 PRACTICAL RECOMMENDATIONS
- If the system air contains much humidity and oil it is required to
use a drying filter to avoid excessive oxidation and wear of
consumable parts, to avoid torch damage or to reduce speed
and quality of cutting.
- Impurities of air favour oxidation of electrode and nozzle and
make it difficult to start pilot arc. If this occurs, clean the end part
of electrode and inside the nozzle with fine abrasive paper.
- Make sure that new electrode and nozzle to fit are clean and
degreased.
- To avoid damage of torch, always use original spares.

3.6 TORCH MAINTENANCE

Always disconnect the unit before any repair of torch.
1) Replace wear parts (picture 11 – 11a)
The parts subject to wear are electrode A, diffuser B and nozzle
C. Either part may be only replaced after loosening nozzle holder
D.
Electrode A should be replaced when a 1/16" (1,5 mm) deep
central crater develops (see pict. 12).
ATTENTION! When unscrewing the electrode, do not make
sudden stresses but gradually force so as to have the
thread unlocked. Lubricate the thread of the new electrode
with silicone lubricant (supplied with the unit). This new
electrode is to be screwed in its housing and locked without
tightening.
Nozzle C should be replaced when its central hole is damaged or
enlarged with respect to the new part (see picture 13). Use of
worn electrode quickly wears out the nozzle. Excessive use of
electrode causes overheating and reduces the life of diffuser B.
Make sure that after replacing it, nozzle D is tight enough.
ATTENTION! Nozzle holder D should be only screwed on
head when electrode A diffuser B and nozzle C are
assembled.
2) Replace torch body E (see picture 11 – 11a).
Remove screw V. Withdraw handle F from body E by swaying it
and making sure that button wires are not torn when separating
both parts. Withdraw the G and H safety contacts wires.
Withdraw the contact L. Unscrew fitting I after cutting the
insulating hose K. Fit the new torch body following all above
operations in reverse order. Fitting I is insulated by shrink hose K
stuck to the fitting when heated by a small source (ex. a lighter).
Before placing handle, make sure that cables are far away from
each other and that fittings are tightly secured.
3) Substitution of adapter W. Only for item 424 (see picture
11a)
Remove ring nut Z and cut the clamps locking cable R. Loosen
screw Y and extract cover X. Extract the control cable pins N and
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