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Cathodic cleaning

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  • Cathodic cleaning

    Am I confused? As I understand, cathodic cleaning action happens only during the electrode positive portion of the ac cycle,(workpiece negative as the electrons are leaving the workpiece to jump to the electrode.)

    My near new Diversion is a 72%EN or 28% EP, with square wave

    I bought a Dialarc 250 HF with water TIG. It being a transformer machine I think AC balance is 50%, with sine wave. It is said to be "high frequancy", though I don't know how high that is. Shouldn't this mean more cleaning action? It doesn't seem to be the case. Is this normal? Can it be fixed?
    Last edited by Willie B; 12-17-2013, 10:43 AM. Reason: More Info

  • #2
    Originally posted by Willie B View Post
    Am I confused? As I understand, cathodic cleaning action happens only during the electrode positive portion of the ac cycle,(workpiece negative as the electrons are leaving the workpiece to jump to the electrode.)

    My near new Diversion is a 72%EN or 28% EP, with square wave

    I bought a Dialarc 250 HF with water TIG. It being a transformer machine I think AC balance is 50%, with sine wave. It is said to be "high frequancy", though I don't know how high that is. Shouldn't this mean more cleaning action? It doesn't seem to be the case. Is this normal? Can it be fixed?
    While no one had a response to my question, I did unearth more information:
    A transformer machine produces a 50/50 balance between EP & EN at 60 HZ, with a superimposed High Frequency of up to 3500 HZ at up to 1000 Volts.
    While balance is at 50%, Electrode positive half of the cycle, current is limited because the oxide layer on aluminum isn't easily conductive, as it displaces air, the air between the electrically charged points is not as easily ionized. The arc from work to tungsten is weakened. Tungsten heating, and cleaning action are limited. In low frequency such as 60 HZ machines the needed ionization of air is lost twice a cycle. In square wave the direction of flow changes and builds to a peak quickly enough to carry the ionization over to the next half cycle. It is the re ionization of air that is responsible for the willy nilly nature of arc wander. Old technology machines used HF High voltage power to establish ionization the high current low voltage arc could follow.
    Think of a lightning bolt, electrons rush down a path of ionized air until they reach a point where the air isn't ionized, here they pool for an instant until sufficient electron numbers, (voltage strength), ionizes another "step leader", then electrons rush to the next pool. The process repeats thousands of times until it reaches the ground. All this happens in a tiny fraction of a second. When we see lightning our eyes aren't quick enough to see the steps, yet we see the random direction each step leader moves describing a jagged line from cloud to earth.

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    • #3
      Originally posted by Willie B View Post
      While no one had a response to my question, I did unearth more information:
      A transformer machine produces a 50/50 balance between EP & EN at 60 HZ, with a superimposed High Frequency of up to 3500 HZ at up to 1000 Volts.
      While balance is at 50%, Electrode positive half of the cycle, current is limited because the oxide layer on aluminum isn't easily conductive, as it displaces air, the air between the electrically charged points is not as easily ionized. The arc from work to tungsten is weakened. Tungsten heating, and cleaning action are limited. In low frequency such as 60 HZ machines the needed ionization of air is lost twice a cycle. In square wave the direction of flow changes and builds to a peak quickly enough to carry the ionization over to the next half cycle. It is the re ionization of air that is responsible for the willy nilly nature of arc wander. Old technology machines used HF High voltage power to establish ionization the high current low voltage arc could follow.
      Think of a lightning bolt, electrons rush down a path of ionized air until they reach a point where the air isn't ionized, here they pool for an instant until sufficient electron numbers, (voltage strength), ionizes another "step leader", then electrons rush to the next pool. The process repeats thousands of times until it reaches the ground. All this happens in a tiny fraction of a second. When we see lightning our eyes aren't quick enough to see the steps, yet we see the random direction each step leader moves describing a jagged line from cloud to earth.
      TIG Welding for dummies came with my Diversion. It talks about High Frequency arc stabilization in transformer based welders as "up to almost a million hertz." In a caption under the illustration it says 16000 HZ. It talks of very high voltage without specifying. Miller manual says if higher voltage is needed widen point gap up to .012, or as narrow as possible (.008) to reduce radio wave transmission.

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      • #4
        Willie

        here is a video on AC balance that may help explain it..

        http://www.youtube.com/watch?v=RG4ZOwSw9CQ#t=196

        Comment


        • #5
          A "Magnetic Amplifier" welder like a Dialarc has NO ability to adjust AC balance...and are fixed at 50/50 balance

          "Chopper" welders like the Syncrowave have the ability to adjust that balance..

          "Inverter" welders like the Dynasty have the additional ability to adjust frequency and waveform..

          http://www.millerwelds.com/resources...lance-Control/

          http://www.youtube.com/watch?v=u-daLs9Q7ac

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