Start, Figure B.23 | Lincoln Electric SVM185-A instruction

B-38

OPERATION

B-38

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EXAMPLE 5 - 4 STEP TRIGGER: Manual control of Start and Crater times with Burnback ON. The 4 step trigger sequence gives the most flexibility when the Start, Crater and Burnback functions are active. This is a popular choice when welding aluminum because extra heat may be needed during Start and less heat desired during crater. With 4 step trigger, the welder chooses the amount of time to weld at the Start, Weld and Crater settings by using the gun trigger. Burnback reduces the occurrence of wire to sticking into the weld pool at the end of a weld and conditions the end of the wire for the next arc start. ( See Figure B.23)

In this sequence,

PREFLOW:

Shielding gas begins to flow immediately when the gun trigger is pulled.

STRIKE:

After preflow time expires, the power source regulates to the start output and wire is advanced towards the work piece at the Strike WFS. If an arc is not estab- lished within 1.5 seconds, the power source output and wire feed speed skips to the weld settings.

START:

The power source welds at the start WFS and voltage until the trigger is released.

UPSLOPE:

During upslope, the power source output and the wire feed speed ramp to the weld settings throughout the start time. The time period of ramping from the start settings to the weld settings is called UPSLOPE.

WELD:

After upslope, the power source output and the wire feed speed continue at the weld settings.

DOWNSLOPE:

As soon as the trigger is released, the wire feed speed and power source output ramp to the crater settings throughout the crater time. The time period of ramping from the weld settings to the crater settings is called

DOWNSLOPE.

CRATER:

During CRATER, the power source continues to supply output at the crater WFS and voltage.

BURNBACK:

When the trigger is released, the wire feed speed is turned OFF and the machine output continues for the burnback time.

POSTFLOW:

Next, the machine output is turned OFF and shielding gas continues until the post flow timer expires.

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Trigger Pulled
Idle	Preflow

Shielding On

Arc Established

Strike

Trigger Released

Start

FIGURE B.23

4 Step Trigger

Start = ON

Crater = ON

Burnback = ON

Upslope Weld

Trigger Pulled

Down slope

TriggerReleased
Crater Burnback Postflow	Idle

Return

Gas

Off

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Power

Wel d

1.5 sec max .

Burnback Time

Source