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Thread: Lack of shielding gas

  1. #1
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    Lack of shielding gas

    I have been having really poor welds lately. I have been extra careful to clean well before starting etc but I still get really bad porosity.

    My 25-75 CO2-Ar is at about 24cfph. I turned my feed way down and felt the nozzle on my cheek and can feel gas coming out.

    Welds start good but then start to deteriorate as I go. I get surface porosity and grapes of very porous material if I weld near an edge.

    I pulled my gun out and reinstalled it. It seems SUPER hard to remove and shove in, is there anything I can lube the o-rings with? Glycerin? Mig wire cleaning solution? I am assuming this shouldn't be so hard to shove in. It should go in until the brass of the lead contacts the aluminum of the roller assembly right?

    Any ideas are appreciated. This is a real piss off. Especially when you do the extra effort to "over" clean the metal first.

    PS Miller DVI-2, welding 1x1x.100" tubing on a 45 degree corner. Voltage @ 3, feed @ 45.

  2. #2
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    Re: Lack of shielding gas

    You could have a leak in you gas hoses or an obstruction somewhere. Standard secondary pressure from a mig regulator is 50 to 80 psi. The pressure builds up in your feed hose and surges out on start for up to a second or more at start. Then the pressure equalizes from 3 to 8 psi when the solenoid is kept open.

    What could be happening is a sufficient amount of gas is reaching the nozzle at start, then petering out. I use portable flowmeters to confirm continuous flow. Here is a recent discussion. http://weldingweb.com/vbb/showthread.php?t=103021
    Last edited by shovelon; 03-25-2012 at 09:55 PM. Reason: tired
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  3. #3
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    Re: Lack of shielding gas

    So I borrowed a gun tip flowmeter from Praxair. With the bottle set at 26cfh I would get about 10 in the first puff and then nothing. I cranked the bottle WAY up and I could get about 10cfh after the first puff.

    Shopped around for a new gun. I figured since I had to buy one I would get a Q-gun. The M-10 my welder came with is pretty junky.

    The only one I could find in town that wasn't a small (150A) one is a 400A Q-gun. I ended up getting this gun for $290. It is pretty big but it has the swivel head, really nice curved handle, oversize machine end, etc. I figure if I upgrade my DVI-2 at some point I would be better off bigger than smaller.

    Also the rating for a gun is only 60% when you use mix gas. I normally use 25-75 so bigger is better in this sense.

    Now I am wondering how long I have had a gas problem. I thought I was being lazy with my cleaning but I think this has been going on for a while too. I was doing MAW vs GMAW for a while I guess!

    Thanks for the tip. I have ordered my own flowmeter. Anyone with a MIG welder should own one of these and check from time to time.

  4. #4
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    Re: Lack of shielding gas

    It sounds like you have a pinched line. make sure you do not have a restriction around the regulator or in the hose leading from the gas solenoid to the gun bayonet connection.
    To test simply lossen off the wire feed rolls then pull the trigger. Check for loss of flow at the nozzle first like you have done then at the hose leading to the gun connection then next to the gas solenoid if you can access, If you have no loss of flow at the gun bayonet connection then the restriction is between there and the gun nozzzle.
    With the symptoms you describe I have discovered in one case that the bottle when chained up was pinching the line running from the flowmeter to the machine.

  5. #5
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    Re: Lack of shielding gas

    lotechman,

    It was my gun. That's why I replaced it with the Q-gun. I deal with KMS in Kamloops and they would have taken the gun back if I still had a problem but it works fine with the new gun.

    As I mentioned it is a little big but such a nice gun. It's amazing how useful the swivel head feature of the Q-guns is! Such a simple idea but I have only welded for a few hours since I got it and I have used it on 2 different projects! You can make your position super comfortable.

    Sean.

  6. #6
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    Re: Lack of shielding gas

    sean,

    Hate to burst your bubble but the Bernard Q 300's with Miller back end are available on E-Bay all the time for between $100-150 shipped.

    Miller ships their wirefeeders with the Bernard Q 300/400 feeders. Lots of commercial users have their own preferences for guns (plus spare parts) and therefore don't take the Bernard guns. Think they're then resold in lots. I've bought several for my Miller welders.
    Syncro 250 DX
    Dynasty 200 DX
    MM 251 w/30A SG
    XMT 304 w/714 Feeder & Optima Pulser
    HH187
    Dialarc 250 AC/DC
    Hypertherm PM 1250
    Smith, Harris, Victor O/A
    Smith and Thermco Gas Mixers
    Access to a full fab shop with CNC Plasma, Water Jet, etc.

  7. #7
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    Re: Lack of shielding gas

    SundownIII,

    You must be looking at a different ebay because the cheapest one on ebay right now is $200 plus shipping. I got a 400 feeder for $290 off the shelf in town. I am not crying over the extra few bucks in convenience cost that allowed me to get some work done this weekend.

    PS I am in Canada so buying just about anything is a slightly different affair.

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