Remote Control Operation; Benefits Of The Precision Tig® 225 - Lincoln Electric PRECISION TIG SVM186-A Service Manual

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REMOTE CONTROL OPERATION

A Foot Amptrol is included with the PRECISION TIG®
225 Ready-Pak models and available for other models
(See Accessories Section) for remote current control
while TIG welding. An optional Hand Amptrol may also
be used. An optional Arc Start Switch may be used to
start and stop the welding if no remote control of the
current is desired. Refer to the Accessories Section
of this manual.
Both the Hand and Foot Amptrol work in a similar man-
ner. For simplicity, the following explanation will refer
only to "Amptrols", meaning both Foot and Hand mod-
els. The term "minimum" refers to a foot pedal in the
"up" position, as it would be with no foot pressure, or a
Hand Amptrol in the relaxed position, with no thumb
pressure.
"Maximum" refers to a fully depressed Foot Amptrol,or
a fully extended Hand Amptrol.
When the welder is in TIG modes activating the
Amptrol energizes the electrode terminal and varies
the output welding current from its minimum value of 5
Amp (DC) or (AC), to the maximum value set by the
Current Control on the control panel. This helps elimi-
nate accidental high current damage to the work piece
and/or tungsten, and provides a fine control of the cur-
rent. When the welder is in the stick mode a remote
control has no effect and is not used.
It is important to note that, in some cases, the tungsten
will not start an arc at the minimum current because
the tungsten may be too large or cold. To start an arc
reliably, it is important to depress the Amptrol far
enough so that the machine output current is near the
tungsten operating range. For example, a 3/32" tung-
sten may be used on DC- to weld over the full range of
the machine.
To start the arc, the operator may have to turn the cur-
rent control up and depress the Amptrol approximately
1/4 of the way down. Depressing the Amptrol to its min-
imum position may not start the arc. Also if the current
control is set too low, the arc may not start. In most
cases, a large or cold tungsten will not readily establish
an arc at low currents. This is normal. In Direct Current
mode the PRECISION TIG® 225 will start a 3/32", 2%
thoriated tungsten electrode at 15 amperes provided
the electrode tip is properly grounded and not contam-
inated.
OPERATION
BENEFITS OF THE PRECISION TIG® 225 DESIGN
In AC TIG welding of aluminum, the positive portion of
the AC wave provides cleaning (removal of aluminum
oxide) of the work piece. This is desirable on materials
with a heavy oxide coating. However the positive por-
tion may also cause the electrode to overheat at high
currents causing "tungsten spitting". The negative por-
tion of the AC wave offers no cleaning action but con-
centrates more heat on the work.
The AC waveform of the PRECISION TIG® 225 opti-
mizes cleaning and heating of the work. The result is
the capability to weld through the complete range in AC
TIG or DC- TIG requiring only one electrode, a 3/32"
2% thoriated tungsten.
PRECISION TIG® 225
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