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  1. #1
    Join Date
    Dec 2005
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    Georgia
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    13

    AC vs DC on a stick welder

    Just gotta ask....it seems as though everyone I talk to says that DC is easier to weld with. Why?

  2. #2
    Join Date
    Mar 2006
    Location
    Manchester, NH
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    With AC your current is switching between positive and negative 120 times each second. At the instant of the switch your arc is actually go out and then has to re-establish.

    With DC there is no switching. You have a smooth, stable arc. The difference between AC and DC welding is instantly noticeable, with everyone preferring DC. However, if all you have is an AC machine, you can still make perfectly acceptable welds with that too.
    Miller Dynasty 200DX
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  3. #3
    Join Date
    Sep 2005
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    1,051

    specialty electrodes

    Howdy Howdy!

    Sometimes you can get specialty electrodes for AC machines. They work similar, but don't run quite as nice as DC. Such as 6011 or 7018 AC-DC If an AC machine is all you have or can afford, then use it with the right rod, and it can get er done with some practice. But if your buying, and can afford it, it is definately worth getting the DC. The AC rods have an arc stabilizer in it, that helps maintain the ionized gases between arc cycles. Good luck! Brian Lee Sparkeee29

  4. #4
    Join Date
    Dec 2007
    Location
    Houston, Texas
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    370
    One of the major places you need an AC machine is in ship building, when welding into a corner and arc blow becomes a problem. It takes an AC machine to overcome this. John
    Long time Teacher - Processes
    Owner - 2 LWS's
    Hobart - Lincoln- Miller - ESAB(Linde)

  5. #5
    Join Date
    Dec 2005
    Location
    Georgia
    Posts
    13
    First, thanks everyone for the reply. I have access to AC/DC combo machines....so using either isn't a problem. I now understand why DC is prefered....guess I should have paid more attention in my farm electrical class and maybe that would have come to me before.

    Quote Originally Posted by weldgault View Post
    One of the major places you need an AC machine is in ship building, when welding into a corner and arc blow becomes a problem. It takes an AC machine to overcome this. John
    John, could you explain what you mean by this? I don't really understand why the AC would become necessary.

  6. #6
    Join Date
    Feb 2004
    Location
    Los Angeles
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    Ed Conley
    Screaming Broccoli, Inc
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  7. #7
    Join Date
    Dec 2005
    Location
    Georgia
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    Quote Originally Posted by Broccoli1 View Post
    That'll work......thanks.

  8. #8
    Join Date
    Oct 2006
    Location
    Plymouth MA
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    273
    On my old Lincolns, the leads are bolted on DC+(never need nuthin' more). The only place I ever use AC is aluminum tig, or big 7024(it makes such a nice bead) in the shop.
    "Weld It And You Won't Be Screwed"
    Rescued from the boneyard SA-250 on a fully equipt trailer (My Wife's Explorer cries every time I hitch up)
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  9. #9
    Join Date
    May 2007
    Location
    schurz
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    249
    well as some ppl know i love ac and i prefer it over dc and there are ppl out there that will argue and tell me in wrong but its just based on yur preference i like the ac for iron powder electrodes and 6011 but i will use dc is if i have to use the 7018 or a 6010 yeah
    it is always better to be long than to too short.

  10. #10
    Join Date
    Feb 2008
    Location
    Western Colorado
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    18
    Quote Originally Posted by injun joe View Post
    well as some ppl know i love ac and i prefer it over dc and there are ppl out there that will argue and tell me in wrong but its just based on yur preference i like the ac for iron powder electrodes and 6011 but i will use dc is if i have to use the 7018 or a 6010 yeah
    Yeah, I've got a portable that's AC/DC but in the shop I've got a couple of 225 AC machines (Miller and Forney). I use a hi-frequency unit on the Miller a lot with 7018, 6010 and such. The Forney is pretty sweet with 6011. Heck, most of the portable work I'm doing now days I use the AC & 6011 there too.

  11. #11
    Join Date
    Mar 2003
    Location
    Brethren, Mi
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    11,403
    I agree with Tozzi, go to almost any professional job and you will find DC machines with the leads bolted to DC+ fir stick work. The only reason for a home hobby type to ever use AC is for nickle work on occasion.

  12. #12
    Join Date
    Oct 2007
    Location
    Libertyville, IL
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    472
    There is one thing that makes me wonder. There're tables that specify current range for certain electrode diameters. For some reason, they do not distinguish between AC and DC. So if an electrode of X size requires 100-140 Amps, it doesn't matter if this is AC or DC.

    If we take into consideration the periodic nature of AC, we very well may suspect that the same electrode would require higher AC current (vs. DC). However, I have never seen any mentioning of this in the literature.

    So, if we trust that it doesn't matter, then many of the smaller AC/DC units will provide a significantly wider range of capability in AC mode (let's say, 230A @AC vs. 150A @DC).

    Please correct me if I'm wrong.
    Last edited by MichaelP; 02-27-2008 at 10:22 PM.

  13. #13
    Join Date
    Nov 2007
    Location
    McDonough Georgia
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    22
    AC will normally require a higher amperage than DC due to the nature of the type power. This is also noticed when using different polarities in DC. Positive electrode will provide less heat to the work piece than negative electrode due to the fact that the current flow is negative to positive always in DC mode. Negative electrode will provide a steady current flow to the work piece thus providing more heat.

  14. #14
    Join Date
    Jan 2004
    Location
    Browns Valley, CA
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    8,518
    Quote Originally Posted by MichaelP View Post
    There is one thing that makes me wonder. There're tables that specify current range for certain electrode diameters. For some reason, they do not distinguish between AC and DC. .
    I've never seen a table that didn't say what polarity or voltage the references were for. You may have not had all of the information, such as a cover sheet or the like.

    A table on the front of a buzzbox is a different story - it's only got AC!

    Hank
    ...from the Gadget Garage
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  15. #15
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    Oct 2007
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    Libertyville, IL
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    Quote Originally Posted by hankj View Post
    I've never seen a table that didn't say what polarity or voltage the references were for.
    Here're some of the Miller/Hobart tables: http://www.hobartwelders.com/elearning/#stick

    http://www.millerwelds.com/pdf/spec_sheets/AD8-0.pdf

    http://www.millerwelds.com/education...calculator.php

    Same table is on my Thunderbolt AC/DC unit. Similar tables I found in the majority of my books. "Welding Essentials", however, does distinguish between AC and DC assigning slightly higher (~10-20%) amperage for the AC mode.

    Now back to the "permanently bolted to DC electrode". It is understandable for welders that provide similar current range in both AC and DC (let's say, up to 300 A in both modes). But when we're talking about something like Lincoln AC/DC 225A/125A or Miller Thunderbolt XL AC/DC 225A/150A, we can see that they have a potential to employ significantly thicker electrodes in the AC mode. Using the above mentioned "Welding Essentials" table (p.139) that distiunguishes between those modes, we can see that the AC/DC Lincoln can use up to 1/4" E6011 electrode in AC mode, but will be limited by 3/16" stick in DC. Whether this capability is important is a different story.

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