Lincoln Electric SQUARE WAVE TIG 355 Service Manual page 24

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At Maximum, the arc will be more forceful and less
prone to sticking but will produce more spatter.
12. PREFLOW
This control adjusts the amount of time the gas and
water valves are open before the arc starts. It is
adjustable from 0 to 10 seconds.
The Preflow time occurs only if the valves were
closed (no gas flow) when the Arc Start switch or
Amptrol was pressed. If a new weld is started
while the gas valve is still on during the Afterflow
time of a previous weld, the Preflow time is
bypassed since gas shielding is already present.
This allows new welds to start immediately with no
preflow delay.
Note that since the arc cannot start during the
Preflow time, a long Preflow setting can cause
complaints about arc starting.
Preflow time of 0.5 seconds is satisfactory for most
applications.
13. SPOT CONTROLS
Spot Switch — A two-position toggle switch:
Recommended for use in the 2-step Arc Start
Switch mode only.
ON: Spot Time control is active. Once the arc is
established, the Spot time begins. At the end of
the Spot time (or if the Arc Start switch/Amptrol is
released sooner), the arc stops. (If Crater Fill [Item
16] is on, downslope begins.)
OFF: Locks out the Spot Time control.
Spot Time Control: Not active if the Spot switch is
off. Adjusts weld time from 0.1 to 5 seconds. Weld
time is the time from when the arc is fully estab-
lished until the arc is turned off (or when Crater Fill
downslope is started). The Arc Start switch or
Amptrol must be held down during the Spot time; if
it is released before the end of the Spot time, the
arc will be turned off (or Crater Fill started).
14. START CONTROLS
Start Switch — A two-position toggle switch:
ON: Start Current control is active. At the begin-
ning of the weld, current will be the value preset by
the Start Current control.
Amptrol has no effect on this current.
OFF: Locks out Start Current and Time controls.
Start Current Display Pushbutton
OPERATION
In general, a
15. PULSE CONTROLS
The position of the
SQUARE WAVE TIG 355
Press and hold in this pushbutton to display the
Start Current preset by the Start Current control.
(The Volts/Amps switch (Item 7) must be in the
"AMPS" position to read preset current.)
Start Current Control
Locked out if the Start switch is off.
Presets the current that will be provided at the start
of the weld. The current can be preset from 2 to
400 amps. The position of the amptrol has no
effect on the initial current.
Current is displayed on the Ammeter when the
pushbutton is pressed before welding.
A "hot" start is used to quickly heat the tungsten
and work, usually on DC TIG welding.
Start Current higher than what the welding current
will be. After the time is set on the Start Time con-
trol, the current will step down to the current set
and controlled by the Peak Current control (Item 6)
and the Amptrol.
A "soft" start is used to preheat the tungsten and
work, usually on AC TIG welding. Set the Start
Current lower than what the welding current will be.
The arc will establish at the Start Current and then
ramp up to the current set and controlled by the
Peak Current control (Item 6) and the Amptrol. The
time to get up to welding current is set by the Start
Time control. During the ramp up, the Amptrol will
affect the current that the ramp is going toward and
therefore the rate at which the current increases.
Start Time Control
Locked out if the Start switch is off. Adjusts the
Start Time from approximately 0.1 to 10 seconds.
Pulse Switch — A two-position toggle switch:
ON: Pulsing will begin as soon as an arc is estab-
lished and will continue until the weld is completed.
If you are using Start Controls, pulsing begins after
the Start Current. If you are using Crater Fill, puls-
ing will continue during the downslope period.
OFF: Locks out Pulse controls.
Pulses per Second Control — Controls the num-
ber of pulses per second from approximately 0.1 to
10 pps. 0.1 pulses per second is slow pulsing (one
pulse every 10 seconds); 10 pulses per second is
fast pulsing.
Background % Peak Current Control — Controls
the background (low pulse) current from zero to
100% of the peak current set and controlled by the
Peak Current control (Item 6) and the Amptrol.
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The present Start
Set the