project: lowering flowrates for dual shield flux core
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  1. #1
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    project: lowering flowrates for dual shield flux core

    So ever since I learned about dual shield flux core, I had this nagging suspicion. The larger flowrates "required" by some literature might be due (in part) due to the very long CTWD necessitated by the DSFC process. With 0.045" E71T-1C/1M, the process needs about ¾ - 1" of "stickout" from the tip, so I could definitely understand needing upwards of 40+ CFH to make sure the shielding gas covers the spread considering that most MIG guns either have the contact tip flush or just slightly recessed; so the nozzle orifice itself is anywhere from 1" to perhaps 13/16" away if it happens to have a recessed tip. So I thought, what if the nozzle was simply longer, to the point where the nozzle orifice was approximately 3/8" away from the weld joint, similar to what on would use with short-circuit MIG with typical wire diameters? Would it still "work"? I'm only a hobbyist, so "work" has a looser definition for me than a professional, so what they heck, try it out.

    So I got bought some extra nozzles, chucked them up in the lathe sliced them up to make a predetermined nozzle length (in order to "bury" the contact tip with a huge recess) and cobbled together a longer frankenstein nozzle to try out.

    Here you can see my standard nozzle (the nickel-plated copper one), and the new mega nozzle. 82.2mm vs 92.5mm. With this setup, I only need 3/8" - 7/16" stand-off distance from the nozzle to the work, while still achieving about 7/8" of actual stickout/CTWD. First try with only 27CFM of C25 worked great. Close enough to the work to really cut down the shielding gas use, but far enough that it doesn't obstruct the view.



    I basically took a cylindrical nozzle, and took off a length, and attached the top of standard conical nozzle so as to have them meet on the flat part and not the taper, and just spot welded it all the way around. Didn't use any filler or anything, just autogenous tacks all the way around. It just needed to not fall off.



    Other than the nozzle getting hotter because it is closer to the arc, worked out great for me. I guess if I feel really ambitious I could add water-cooling to the nozzle to wick-out the heat, but that will be a project for another day. Of course I could be totally wrong, but for now I'll run with it when/if I should end up using dual shield.
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  2. #2
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    Re: project: lowering flowrates for dual shield flux core

    You should make a gas lens nozzle
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  3. #3
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    Re: project: lowering flowrates for dual shield flux core

    I’ve none somewhat similar with Mig by shortening the tip thus increasing the nozzle shielding slightly.


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  4. #4
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    Re: project: lowering flowrates for dual shield flux core

    Who says you need that much stickout? I weld that crap every day, I don't use 1 inch of stickout.

  5. #5
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    Re: project: lowering flowrates for dual shield flux core

    Quote Originally Posted by TimmyTIG View Post
    Who says you need that much stickout? I weld that crap every day, I don't use 1 inch of stickout.
    Most literature spec's out roughly 3/4" of stickout, including Lincoln.





    Quote Originally Posted by Lis2323 View Post
    I’ve none somewhat similar with Mig by shortening the tip thus increasing the nozzle shielding slightly.


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    I thought about that, but that would require shortening a new tip everytime you want to change out the tip. With this nozzle, it's a 1-time deal, and I can just use any appropriately sized tip without having to shave it down.

    Quote Originally Posted by Louie1961 View Post
    You should make a gas lens nozzle
    I already have the screens. Just need to make a custom punch-out tool
    Last edited by Oscar; 08-27-2019 at 02:36 PM.
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  6. #6
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    Re: project: lowering flowrates for dual shield flux core

    All I can tell you is when some worm on the other shift turns the gas down too low and I don't notice it, I either get worm tracks or porosity. And a gas lens won't work with MIG cause there's too many sparks.

  7. #7
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    Re: project: lowering flowrates for dual shield flux core

    Quote Originally Posted by TimmyTIG View Post
    And a gas lens won't work with MIG cause there's too many sparks.
    challenge accepted!
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  8. #8
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    Re: project: lowering flowrates for dual shield flux core

    Quote Originally Posted by TimmyTIG View Post
    Who says you need that much stickout? I weld that crap every day, I don't use 1 inch of stickout.
    times two.

  9. #9
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    Re: project: lowering flowrates for dual shield flux core

    Quote Originally Posted by lars66 View Post
    times two.
    Exactly. The other thing the shielding gas does is cool the weld and the mig gun. Personally I would rather buy the gas and save the mig gun. Why not use co2 if gas usage is an issue?
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  10. #10
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    Re: project: lowering flowrates for dual shield flux core

    Quote Originally Posted by M J D View Post
    Exactly. The other thing the shielding gas does is cool the weld and the mig gun. Personally I would rather buy the gas and save the mig gun. Why not use co2 if gas usage is an issue?
    Depends on the wire as which gas/gases you can use.

  11. #11
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    Re: project: lowering flowrates for dual shield flux core

    Quote Originally Posted by TimmyTIG View Post
    Who says you need that much stickout? I weld that crap every day, I don't use 1 inch of stickout.
    I'm with this, I never run anywhere near 3/9 inch of stick out, closer to 3/8th at the most, down to 1/4 most of the time, i'm not sure why the manufacturer spec out that much stick out, but I've passed many a weld test, and even qualified quite a few new procedures with half the stick out.

  12. #12
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    Re: project: lowering flowrates for dual shield flux core

    Quote Originally Posted by M J D View Post
    Exactly. The other thing the shielding gas does is cool the weld and the mig gun. Personally I would rather buy the gas and save the mig gun. Why not use co2 if gas usage is an issue?
    I know it's odd, but gas usage is not an issue for me. I can afford all the shielding gas I ever need. So why do I do this crazy stuff? Just to see if I'm right, and if I can prove that I'm right about my thoughts.
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  13. #13
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    Re: project: lowering flowrates for dual shield flux core

    What's messed up about dual shield is when it's throwing massive porosity, you can't even really tell it's happening. That's why I don't fool with the gas. That thing can make a huge mess in a hurry.

  14. #14
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    Re: project: lowering flowrates for dual shield flux core

    I just made another one for one of my smaller MIGs, that uses an MB24KD mig gun. This is for running 035 dual shield.



    In this one, I integrated from the beginning, a slight 2.5° downward droop to the conical tip I welded on. This takes into account the downward slope the wire takes when using the mfg recommended stickout.




    Using 0.035 E71T-1C/1M. Ran beautifully. Only needs 5/16" to 3/8" from nozzle-to-work to achieve the mgf required ~7/8" electrical stickout. I only used ~19 CFH for this.




    No porosity or any other such purported issues. Just a nice clean weld without wasting a crap ton of shielding gas.

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  15. #15
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    Re: project: lowering flowrates for dual shield flux core

    Quote Originally Posted by Oscar View Post
    I know it's odd, but gas usage is not an issue for me. I can afford all the shielding gas I ever need. So why do I do this crazy stuff? Just to see if I'm right, and if I can prove that I'm right about my thoughts.
    There it is...experimentation....this is how we came this far in industry, some fella and his curiosity got the best of him, so he plays around with this idea and that idea and pretty soon he has a real solution to something that's been bothering the crap out of him for weeks. Takes that idea to the powers that be and bingo we have a new product or idea on the market.

    Never quit experimenting I do it all the time sometimes it works sometimes it dont

  16. #16
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    Re: project: lowering flowrates for dual shield flux core

    The minimum stickout recommendation for dual shield is to preheat the wire so it has a chance to get any moisture out of the core and avoid hydrogen cracking.

    But 3/4" is CTWD so from the tip to the workpiece. Not how much wire you can see sticking out before it goes into a stream of metal.

    On spray or dual shield, the tip should be recessed at least 1/8" or so. And you'll probably have at least 1/4" from the base metal to the wire end - much more if you are welding heavy stuff or a fillet. So 3/4" total but 1/4" is the puddle & the arc and 1/8" is inside. That leaves you with 3/8" of wire sticking out that you could see - if you're looking from the side.

    If you have a 300 or 400 Amp mig gun with a matching nozzle, 3/8" is not going to look like a lot. It'll look perfectly normal. I think a lot of people that don't think about it, are actually are running 3/4" CTWD with dual shield.

    PS. Some guns have heavy duty nozzles as an option and they are actually a bit longer if you look closer and can have 1/4" recess.
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    Last edited by Pete.S.; 09-05-2019 at 10:04 PM.

  17. #17
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    Re: project: lowering flowrates for dual shield flux core

    what i like about dual shield, is the visibilty from all the clearance from nozzles end. in other words, i like the opposite of what your doing w/ the nozzle, so i can see better. a lil while back, i did a bunch of stainless plate to rebar (flare bevel), so i used 309 dual shield, as it gave good pentration, probally better penn. than any other procedure. i customized a nozzle for that by making it smaller dia. yeah, i proabaly spend more on gas though, but worth it to me

  18. #18
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    Re: project: lowering flowrates for dual shield flux core

    Quote Originally Posted by Pete.S. View Post
    The minimum stickout recommendation for dual shield is to preheat the wire so it has a chance to get any moisture out of the core and avoid hydrogen cracking.

    But 3/4" is CTWD so from the tip to the workpiece. Not how much wire you can see sticking out before it goes into a stream of metal.

    On spray or dual shield, the tip should be recessed at least 1/8" or so. And you'll probably have at least 1/4" from the base metal to the wire end - much more if you are welding heavy stuff or a fillet. So 3/4" total but 1/4" is the puddle & the arc and 1/8" is inside. That leaves you with 3/8" of wire sticking out that you could see - if you're looking from the side.

    If you have a 300 or 400 Amp mig gun with a matching nozzle, 3/8" is not going to look like a lot. It'll look perfectly normal. I think a lot of people that don't think about it, are actually are running 3/4" CTWD with dual shield.

    PS. Some guns have heavy duty nozzles as an option and they are actually a bit longer if you look closer and can have 1/4" recess.

    Yes, I understand this, but perhaps I used my wording too loosely. I should have known better to not inter-change "CTWD" and "stickout". But then again, I'm only a hobbyist. The CTWD is indeed within the range suggested by the literature I have found, which is 3/4-1", which was the basis for all the initial measurements and subsequent modifications.
    Last edited by Oscar; 09-05-2019 at 11:48 PM.
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  19. #19
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    Re: project: lowering flowrates for dual shield flux core

    "If it looks stupid but it works, then it aint stupid".

    We do the opposite with our nozzles here for solid wire short-arc - the MB36 guns, tips and nozzles sold here are nearly always specced for spray transfer, so 1/4" or more recessed tip, and it's hard to find a setup off the shelf that's not like this.
    We simply cut off 1/4" of nozzle to make the tip flush, and therefore keeping a proper electrical stick-out length for short-arc. Doing some heavy work you just swap nozzles. ...if you remember

  20. #20
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    Re: project: lowering flowrates for dual shield flux core

    Kinda the same here, on the nickel plated 36 nozzle, it's recessed roughly 3/16" IIRC. Probably for the pulse-MIG side of things, which uses spray-transfer on the high side.
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