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  1. #1
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    Default UNIMIG RAZOR™ 200 AC/DC Balance Control

    I was looking at the manual for this unit and I was a bit confused when I got the the balance control.

    The manual states:

    9. AC Balance
    Provides selection to adjust the balance of the AC wave form in AC TIG mode.Allows adjustment of the arc to be balanced, penetrating or oxide cleaning duringAC TIG welding. (-5 to +5)

    What exactly does this mean? 50% +/- 5% seems quite inadequate so I must be reading it wrongly.

    Does someone have one or, at least, can someone read better than I can?

    Thanks
    Jack

  2. #2
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    To quickly describe AC balance, imagine a sine wave (can also be square, trapeziod, but let's not complicate).
    A line intersects this waveform, which represents zero volts, where no current is flowing. To the top of this line, we can consider it the electrode positive portion of the waveform, and the bottom is electrode negative. The waveform is constantly changing between DCEN and DECP throughout this waveform. Subsequently, the High frequency arc is firing to help the current push through this zero volt barrier on each cycle of the waveform.

    AC balance is how much time (ie how much area under the curve) is spent either 'positive' or 'negative'.
    The electrode positive section of the wave is the cleaning action of the waveform (breaking down the aluminium oxide layer, seen as 'frosting' on the weld periphery).
    The electrode negative section of the wave is the penetrating action of the waveform (penetrating into the base material to join material).
    Given that these different 'halves' of the wave indicate direction of electron flow, it also influences where the heat balance resides- in the torch side of the equation, or the job side.

    High end machines will give accurate info on what the AC balance setting actually is. Most manufacturers give an arbitrary scale (5- to +5 in your case, by the sounds).
    It seems like 0 = blanaced waveform (50% cleaning, 50% penno)
    -5 would either be high cleaning or penno, (you'll be able to tell on a test piece), and the +5 side will be the other end of the spectrum.

    My EWM Tetrix, when set to zero, corresponds to 65% Electrode Negative (penetrating). and I've got a precise percentage range to work with within that if I need.

  3. #3
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    Quote Originally Posted by Jack Ryan View Post
    Does someone have one or, at least, can someone read better than I can?
    I have one, and I have no clue what the AC balance numbers mean - all I know is that if you change the amps, the AC balance resets to the factory default, which is so very dumb, but Unimig don't care.

    I have tried experimenting with the balance settings to try and work out what gives more heat vs cleaning, and couldn't work it out.

    I've got a current clamp for my oscilloscope which I've been meaning to use to try and see what's actually going on, but the welder and scope are at opposite ends of the workshop, and haven't got quite motivated to move one close enough to the other to do any testing.

  4. #4
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    Quote Originally Posted by Commander_Keen View Post
    To quickly describe AC balance, imagine a sine wave (can also be square, trapeziod, but let's not complicate).
    A line intersects this waveform, which represents zero volts, where no current is flowing. To the top of this line, we can consider it the electrode positive portion of the waveform, and the bottom is electrode negative. The waveform is constantly changing between DCEN and DECP throughout this waveform. Subsequently, the High frequency arc is firing to help the current push through this zero volt barrier on each cycle of the waveform.

    AC balance is how much time (ie how much area under the curve) is spent either 'positive' or 'negative'.
    The electrode positive section of the wave is the cleaning action of the waveform (breaking down the aluminium oxide layer, seen as 'frosting' on the weld periphery).
    The electrode negative section of the wave is the penetrating action of the waveform (penetrating into the base material to join material).
    Given that these different 'halves' of the wave indicate direction of electron flow, it also influences where the heat balance resides- in the torch side of the equation, or the job side.
    Thanks for that explanation and I apologise for my lack of clarity but I know what AC balance is, I just don't understand the Unimig parameters. Typically AC balance might be set to 70% meaning that 70% of the time the machine is operating DCEN. Plus or minus 5 means nothing to me - it can't possibly mean plus or minus 5%.


    High end machines will give accurate info on what the AC balance setting actually is. Most manufacturers give an arbitrary scale (5- to +5 in your case, by the sounds).
    It seems like 0 = blanaced waveform (50% cleaning, 50% penno)
    -5 would either be high cleaning or penno, (you'll be able to tell on a test piece), and the +5 side will be the other end of the spectrum.
    That must be what it is but it is hardly intuitive.


    My EWM Tetrix, when set to zero, corresponds to 65% Electrode Negative (penetrating). and I've got a precise percentage range to work with within that if I need.
    I can deal with that OK. The AC balance is just a change in the "mark:space ratio" of the square wave output. It is trivial to convert that to a percentage so I don't know why Unimig didn't.

    Again, thanks for your response - an arbitrary scale it must be.

    Jack

  5. #5
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    Quote Originally Posted by RustyArc View Post
    I have one, and I have no clue what the AC balance numbers mean - all I know is that if you change the amps, the AC balance resets to the factory default, which is so very dumb, but Unimig don't care.

    I have tried experimenting with the balance settings to try and work out what gives more heat vs cleaning, and couldn't work it out.

    I've got a current clamp for my oscilloscope which I've been meaning to use to try and see what's actually going on, but the welder and scope are at opposite ends of the workshop, and haven't got quite motivated to move one close enough to the other to do any testing.
    Are you able to weld aluminium?

    Does your CRO do capture and save? It would be interesting to see what is happening.

    Thanks for your input.

    Jack

  6. #6
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    Maybe this explanation makes more sense ?
    https://www.millerwelds.com/resource...alance-control

  7. #7
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    Quote Originally Posted by Jack Ryan View Post
    I was looking at the manual for this unit and I was a bit confused when I got the the balance control.
    Does someone have one or, at least, can someone read better than I can?

    Thanks
    Jack
    Jack,
    I don't have this welder, however I do have the manual in a PDF file. I think your reading skills are fine. The manual does not mention the
    balance percentages in relation to the plus or minus 5. I think the numbers are arbitrary, perhaps loosely based on percentages.
    It may be just trial and error, find the number that works for you on some test welds with aluminium.

    Regards,
    Paul

  8. #8
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    Quote Originally Posted by droog View Post
    Maybe this explanation makes more sense ?
    https://www.millerwelds.com/resource...alance-control

    Thanks for that but understanding AC balance is not the problem, understanding the Unimig manual is. If I want an AC balance of 70% (70% DCEN) I want to see "70%" on the display (or at worst, 30%). I don't want to see "4" as it means nothing to me.

    Jack

  9. #9
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    Quote Originally Posted by paul33 View Post
    Jack,
    I don't have this welder, however I do have the manual in a PDF file. I think your reading skills are fine. The manual does not mention the
    balance percentages in relation to the plus or minus 5. I think the numbers are arbitrary, perhaps loosely based on percentages.
    It may be just trial and error, find the number that works for you on some test welds with aluminium.

    Regards,
    Paul
    Yes, I think you are right Paul. It seems a shame though that the microprocessor looking after the process couldn't be used for such a trivial calculation.

    Thanks
    Jack

  10. #10
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    Quote Originally Posted by Jack Ryan View Post
    Thanks for that but understanding AC balance is not the problem, understanding the Unimig manual is. If I want an AC balance of 70% (70% DCEN) I want to see "70%" on the display (or at worst, 30%). I don't want to see "4" as it means nothing to me.

    Jack
    Yeah sorry understand now.
    Pretty sure they are just arbitrary numbers. The good thing is next month they will bring out a new model with increased cleaning action and control and mark it as +-10 (


    And just after posting that I find the manual states +-10 on page 8 and 9. Then +-5 on page 12.
    https://unimig.com.au/wp-content/upl...CDC-Manual.pdf
    Last edited by droog; 2nd Jun 2021 at 04:11 PM. Reason: Reference manual

  11. #11
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    Quote Originally Posted by droog View Post
    Yeah sorry understand now.
    And just after posting that I find the manual states +-10 on page 8 and 9. Then +-5 on page 12.
    No problem.

    Their WEB site shows +/- 10 as well. Clearly, I'm not the only one struggling to understand what they mean.

    Jack

  12. #12
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    That's the problem with machines with an arbitrary scale.
    Imagine going from one machine to the next, and having to correlate what values relate to what actual settings. At least when comparing a DCEN percentage value, you can compare between machines.
    It would be a pain in the ass at best. sometimes doing a job by feel is not good enough

    @droog - just like Spinal Tap's Marshall amps which go to 11, for 'that little bit more'

  13. #13
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    Quote Originally Posted by Jack Ryan View Post
    Are you able to weld aluminium?

    Does your CRO do capture and save? It would be interesting to see what is happening.
    It welds aluminium just fine, but with my odd attempt at tweaking the balance, I really haven't been able to work out what's cleaning more and what's penetrating more, it all just looks the same to my very untrained eye.

    My CRO, while digital (HP 54602A), doesn't capture and save in a useful manner, so I'd probably try and video what's going on. I've been eyeing off a new tablet-style CRO for a while, but since the current CRO has been able to solve pretty much all the problems I've needed it for, it's been hard to prioritise its replacement.

  14. #14
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    Quote Originally Posted by RustyArc View Post
    It welds aluminium just fine, but with my odd attempt at tweaking the balance, I really haven't been able to work out what's cleaning more and what's penetrating more, it all just looks the same to my very untrained eye.

    My CRO, while digital (HP 54602A), doesn't capture and save in a useful manner, so I'd probably try and video what's going on. I've been eyeing off a new tablet-style CRO for a while, but since the current CRO has been able to solve pretty much all the problems I've needed it for, it's been hard to prioritise its replacement.
    A video works for me.

    I would have thought it unusual to have a CRO in a fabrication type workshop but I guess not - at least two of us have them.

    Jack

  15. #15
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    Quote Originally Posted by Jack Ryan View Post
    A video works for me.

    I would have thought it unusual to have a CRO in a fabrication type workshop but I guess not - at least two of us have them.
    I'll have to get motivated and move it from the smoke-removal end of the workshop to the metal-ruining end...

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