OPERATION |
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EXAMPLE 3 - 2 STEP TRIGGER: Customized Arc Start, Crater and Arc End. Sometimes it is advanta- geous to set specific arc start, crater and arc ending parameters for the ideal weld. Many times when weld- ing aluminum crater control is necessary to make a good weld. This is done by setting Start, Crater and Burnback functions to desired values. (See Figure B.21)
For 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.
UPSLOPE:
Once the wire touches the work and an arc is estab- lished, both the machine 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.
CRATER:
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.
BURNBACK:
After the crater time expires, 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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Idle
Shielding On 
Gas
Off 
PulledTrigger
Preflow
FIGURE B.21
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| 2 Step Trigger | |||
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| Start = ON | |||
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| Crater = ON | |||
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| Burnback = ON | ||||
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Strike |
| Upslope | Weld | |||||
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ReleasedTrigger
Downslope
Burnback Postflow Idle
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Power | Weld |
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| 1.5 sec max . | ||||
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Source | Start |
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Output | Crater |
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| Off |
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WFS | Weld |
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Crater |
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| Run |
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| Off |
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Start time | Crater ti me |
B urnback Time