Unstable pilot arc

On our welding machine using plasma welding process, unstable pilot arc behaviour occurred. In a difficult to be determined time and condition the pilot arc starts to "flicker" .It can happen directly after starting the arc, after some time (2 -- 3 hours) of arc burning or just after using higher amperage (during welding). When the flickering of the arc occurs the deterioration of the weld quality is observed. With no parameter changed in the program it is visible that the flow and melting of the material is differ-ent.
In case of leakages, dirty installation etc., we have tried a lot, but we haven't found the root yet. We have already checked all electrical connections and work clamps and cleaned everything (also the pipelines, valves, etc.). We have also checked the electrodes, power supply, gas quality, gas pressure, but found nothing. So we really run out of ideas...

Maybe one additional note: We have two automatic welding machines from two different manufacturer. Both worked without any problems and then out of a sudden the same de-scribed problem occurred on both machines.

Thank you very much for every idea!

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• Jul
• 19
• 2011
• 1
• 45
• 29p
• part
• 30s

[seymour86]

could be regulators not keeping constant pressure for the arc flow and as far as your pictures go on welding tip and tricks dot com it Looks like improper flow rates on shielding gas which colud also be caused by faulty regulators. I am not an expert on PAW but I help troubleshoot the ones at my job from time to time. I would say go down the line of the gas flow to see where exactly the problem is as it could be after the regulators.