spool guns??

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Why do these small machines require spool guns to weld aluminium?  I haven't learned mig yet but it seems like they weld aluminium at school without a spool gun. So whats the deal? Why cant you just feed the aluminium wire from in the machine?
Reply:Yes you can. But in the best of all conditions you want a short torch lead, a teflon liner kit, U drive rolls, and large diameter stiff wire like 5356. I have done in the past and it worked. More trouble than it is worth though.Weld like a "WELDOR", not a wel-"DERR" MillerDynasty700DX,Dynasty350DX4ea,Dynasty200DX,Li  ncolnSW200-2ea.,MillerMatic350P,MillerMatic200w/spoolgun,MKCobraMig260,Lincoln SP-170T,PlasmaCam/Hypertherm1250,HFProTig2ea,MigMax1ea.
Reply:Originally Posted by jamesyarbroughWhy do these small machines require spool guns to weld aluminium?  I haven't learned mig yet but it seems like they weld aluminium at school without a spool gun. So whats the deal? Why cant you just feed the aluminium wire from in the machine?
Reply:jamesyarbrough, aluminum wire is less stiff than steel in the same diameter.  Push-only MIG torches have a lined conduit/wire guide that has some 'room inside' for the wire to slide.  Aluminum wire, in those conditions will bend from side to side inside the conduit and that means some of the wire will not feed, it will "coil up" or pile up- so to speak.  Then the coil/pile is 'full' or the conduit has 'accumulated' enough wire and at that second; the wire will rush out into the welding arcs surging the wire speed wildly.The machines we use for MIG are Constant Voltage so the current is (primarily) varied to keep the voltage constant. When the resistance (R) in the equation V=IR, which is the contact tip or wire tip's distance from the parent metal with the 'ground' clamp changes; .... the power supply varies the Current (I) up or down to try to keep the Voltage (V) constant.Therefore if the machine is set to weld at a given voltage, and the wire feed is variable.. the current will be varied in compensation. What usually results is a lot of burn back where the wire is fused to the tip.So imagine you're welding and someone is standing back at the power supply turning up and down the wire speed AND the heat???  not the easiest way to weld.So the weld consistency is poor, the speed of aluminum MIG is usually much higher rate of travel than steel. This means that if you add the wire unpredictably, speeding up and slowing down, to the power supply trying to add or remove current to compensate for the variations in voltage: the result is a very poor quality weld.If you'd really like to get frustrated take an older MIG stretch out, one where the steel wire has left deposits of copper coating, or worn the interior and then run aluminum wire in that....! now that is unpredictable welding torch performance.It can be done; but not in any kind of decent quality, move-around-the-shop, regular day's work circumstances.  The push-only limit to aluminum wire feed is about 10" so the distance from the roll in a spool gun to the tip is usually about that or less to give reliable wire speed so you can do your job without fighting the power supply's control circuit and the weld deposition being inconsistent. Not to mention; the tips burned up will buy the spool gun.If these facts weren't true, then there wouldn't be spool guns for aluminum, not that they aren't useful for other wires too.Cheers,Kevin MorinLast edited by Kevin Morin; 01-01-2013 at 06:59 PM.Reason: typo's
Reply:Aluminium wire has much less rigidity, which causes it to be more likely to crumple-up and "birds-nest" in the feeders.  The solutions that Shovelon mentioned are all ones which keep the wire path shorter, less changes in direction, as well as heavier wire, which has a little more rigidity through its length...With a spool gun, the wire path is very short.  The other production type option is a push-pull gun, in which the wire is still fed through the machine with the large spool, but there is a second motor in the gun itself which works in concert with the drive motor in the machine.  The one in the gun "pulls" the wire while the one in the machine pushes the wire towards the gun...  That works very well, but is an expensive option.  The higher cost machines also use 4 wheels in the feeder, while the lower end machines have 2.
Reply:Well thanx for the info guys. I have only walked down the mig isle a few times at school. But it seems like there is only a couple migs they let students run aluminum on. They dont have spool guns but the torch and cable is a bit larger than the others. Never payed a lot of attention so I cant describe with any real detail.  I only ask because it seems like a spool gun would be heavy and awkward to use.
Reply:Miller Push-Pull on left and Miller MIG on right. They look very similar. Attached ImagesMillermatic 200Hobart Handler 120Victor O/A & Ramco BandsawLincoln 225 ACSnapOn AD HoodMiller XMT304/22AHypertherm Powermax 1650 G3Lincoln Idealarc DC600 w/Extreme 12 VSMiller Digital Elite "Joker"
Reply:Yep thats it. The one one the left... so are they more expensive than a spool gun?
Reply:About $1200 for the gun and about another $1800-2000 for the XR Control unless your machine is setup to run them.Millermatic 200Hobart Handler 120Victor O/A & Ramco BandsawLincoln 225 ACSnapOn AD HoodMiller XMT304/22AHypertherm Powermax 1650 G3Lincoln Idealarc DC600 w/Extreme 12 VSMiller Digital Elite "Joker"
Reply:Wow thats ridiculous.  Probably on costs 30 bucks to make. Lol. Ok so I guess a spool gun would be the way to go then. Again, thanks for the info!
Reply:Originally Posted by jamesyarbroughWow thats ridiculous.  Probably on costs 30 bucks to make. Lol. Ok so I guess a spool gun would be the way to go then. Again, thanks for the info!
Reply:Part of the reason of such a high cost is there is no "hobby" level of this equipment. Hobby welders from Miller, $500-$1200, Miller professional welders, $2400 and up, way up.Millermatic 200Hobart Handler 120Victor O/A & Ramco BandsawLincoln 225 ACSnapOn AD HoodMiller XMT304/22AHypertherm Powermax 1650 G3Lincoln Idealarc DC600 w/Extreme 12 VSMiller Digital Elite "Joker"
Reply:When I bought a Bernard Q300 for my Millermatic 200, I shortened the old gun and installed a Teflon liner for aluminum welding.  I tried 5356 and 4340, 100% Argon.  It fed well, but burned back and stuck to he tip regardless of voltage or WFS settings.  Ruined around 10 tips in an hour.  I still have no idea why it just will not work well when it works off my Spoolmatic with the same power source.  Granted I have very little experience with welding, it just seems like it should work but doesn't.  I guess that's why people shell out a grand for spoolguns.TA Arcmaster 300CM3XMT 304S22P12 suitcase feederX-Treme 12VSOptima pulserTA161SMaxstar 150STLHypertherm PM45OP setupStihl 020AVP, 039, 066 Magnum