How to prevent blow through

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Hi all.   I'm welding a patch panel into some 24 ga. automotive sheet metal, using my Weldpak 100 MIG setup.  As per the chart on the lid I have my voltage set to "A" and the wirespeed to "2".  Using Hobart .24 wire.  C25 gas set to 15 on the flow gauge.I'm having a big problem blowing right through the metal.  Usually it's when I'm striking the arc.  Other times it's when I have a nice bead going. I can't go any lower with the voltage.  I've tried a longer stickout but it pops and doesn't arc very well.What are some other things I can try to prevent this from happening?ThanksCurt
Reply:This is a common problem and for me what I do is what my old welder friend calls 'long arcing'. He tells me to pull the wand away from the work about 1/4 of an inch or so. Hit the trigger and dont hold it down. Just tap the trigger, let off and you will get a much better result. Im not an expert at teaching this technique and I am sure someone here is better at explaining this than me. Really faster on the trigger.
Reply:That's the way I do it on real thin stuff, just run a series of tacks. It gives the base metal a chance to cool down before applying more heat to it.                                             MikeOl' Stonebreaker  "Experience is the name everyone gives to their mistakes"Hobart G-213 portableMiller 175 migMiller thunderbolt ac/dc stick Victor O/A setupMakita chop saw
Reply:and thensproing....it warps.Lincoln Power Mig 210MP MIGLincoln Power Mig 350MP - MIG and Push-PullLincoln TIG 300-300Lincoln Hobby-Weld 110v  Thanks JLAMESCK TIG TORCH, gas diffuser, pyrex cupThermal Dynamics Cutmaster 101My brain
Reply:So you just do a series of real quick tacks?  Do you adjust the voltage or wire speed at all for this method?  Thanks.
Reply:If possible hold a piece of copper or ally behind your weld seam and do a series of short tacks. The copper will act as a heat sink and draw the heat from the panel thus minimizing the distortion. Move around withe your welds and go slowly. Too much heat=big problems
Reply:Originally Posted by RaindemSo you just do a series of real quick tacks?  Do you adjust the voltage or wire speed at all for this method?  Thanks.
Reply:If you want to see a master at work welding patch panels, read this threadhttp://www.garagejournal.com/forum/s...3534&showall=1MillerMatic 252, HTP 221 w/cooler, Hypertherm PM45, Lincoln IdealArc 250 AC/DC"I'd like to believe as many true things and as few false things as possible"
Reply:If you vary the stickout you can momentarily increase or decrease the amperage.  Say you normally run with a 3/8 stickout on light material.  As you notice the heat building up pull back on your gun and run half an inch stickout... This will reduce your amperage.  For light gauge pulling back to 3/4 inch is about the limit.  If you need more heat reduce the stickout.
Reply:Originally Posted by frieedIf you want to see a master at work welding patch panels, read this threadhttp://www.garagejournal.com/forum/s...3534&showall=1
Reply:Welcome to my worldMillerMatic 252, HTP 221 w/cooler, Hypertherm PM45, Lincoln IdealArc 250 AC/DC"I'd like to believe as many true things and as few false things as possible"
Reply:How automotive welding (or thinner material) differs from other types is that you cannot stitch the metals together like a sewing machine. Lets say you have a 1 foot weld to do.. put a short stitch (less than an inch) on one end, then another stitch in the middle, then one on the other end, then rinse and repeat making sure not to weld anywhere near where you just stitched. This keeps the metal cool enough to lessen the warpage problem and eliminates blow-thru. The thinner the metal, the shorter the stitch and the need for more time to let the metal cool. It may look like crap when you are done, but grinding and the appropriate skim-coat of bondo and its better than new. Keep asking and keep looking for answers. I have been doing this for years and learned just like you are.