Newbie strugging with MIG on sheetmetal

[dstaley]

Hello guys,
I'm using my new SP135-T with .021 wire to graft in a replacement toe panel in my old Camaro. I'm having trouble getting a good weld on either of the two lower heat settings (A or B). I suspect my problem is not getting the wire feed right, and I assume the lower heat settings require a more precisely selected wire feed.

I'm running 25/75 CO2/Argon mix at 10PSI FWIW. I have no trouble with heavier welds using either of the two hotter settings.

Thanks for any help you can pass on!

[MicroZone]

If you could post a picture or describe what you consider "having trouble getting a good weld"...then we can help.

Are you burning through? Is the weld not sticking? Is the weld too tall?

[dstaley]

On some settings I could get a sustained arc, but it was a strange hissing arc rather than the typical "frying bacon" nice steady crackle, and it seemed like there was little deposition from the wire. I'm suspecting that was "wire feed too low".

Some other settings resulted in difficulty sustaining a good arc, the "bead" (wasn't much of a bead really) was clumpy and didn't flow properly.

I had trouble homing in on good settings, and I'm pretty sure it was user error. The weldor (me) doesn't work right yet, but the welder seems ok. I'm at work now but I'll try to get some pictures when I get home.

[MicroZone]

Sometimes when trying to weld upside down or reverse vertical, this will happen. Were you trying to do this?

[imagineer]

Use setting "B" or "C" and turn your wire speed up. Using a 155 amp Lincoln, I found that if I used a higher voltage AND higher wire speed AND was in motion as I pulled the trigger AND only made 1" beads, I got decent results putting patch panels on a pick up

[dstaley]

Not yet. I was working a horizontal seam on the front of my firewall. I've only tacked the rest of the panel so far.

I wasn't able to get a long enough bead for a quality stitch weld. I didn't have any trouble tacking but sustaining any more than that was difficult. I'll experiment more tonight if possible, but with the 2 year old it's tough to know what will happen each night!

[dstaley]

OK, I'll try that. I wasn't moving when I tried to start, so I'll try "B" with a little motion and experiment with the wire speed. Thanks!

[Robo48]

Sometimes on thin stuff its tough to NOT burn through. I like to just spot the whole way. Once you get the rhythm down you can make a nice bead and not ruin anything. This is of course my way to not screw anything up as I am just past being a first timer.

[dstaley]

I tried heat setting B and experimented more methodically with the heat setting, keeping in mind some of the new information I've discovered on this site about hold-out. I've done a lot of stick welding with my old Lincoln AC225, but I now understand a little better that MIG welding works differently (the gun should be held with the wire in a much different position than an electrode, must think about wire feed as heat control instead of concentrating on arc gap, must look for different shape fillet since MIG welds don't have a thick slag overcoat, etc). MIG is as different from stick welding as oxy-acetylene welding, but in completely different ways I guess.

I was able to improve my welds to the point where I could almost run a bead along the edge of the scrap sheet material I have. After a short distance it would eventually start melting the sheet badly, but that's probably unavoidable. My wire speed yesterday was insufficient. I also was not concentrating on hold-out, and it makes more difference than I realize- I guess it makes sense that the resistance in the weld wire between the nozzle tip and the arc would greatly affect the arc, so by adjusting the hold-out I'm also adjusting heat.

I've decided I must upgrade my welding helmet before I do much more of this. I have an OTOS Chamelion that worked just fine for stick welding, but for this little MIG it's simply not sensitive enough- it lightens while welding, sometimes doesn't darken reliably, and I don't think it's safe for light welding. Time to finally get a more serious piece of safety equipment I guess.

[Robo48]

Today at work I welded a door catch back on a truck door. I haven't done any sheetmetal work with the 135+ at work WOW what a machine. It is really where the smaller welders shine. I couldn't believe how well it runs on thinner metal. The welder was on E 3 with .030 wire if that helps you any. I am guessing either tap A or B for you and somewhere near the bottom of the wire speed. Hope this helps I am not a very good welder but was very impressed with the little guy today

[dstaley]

I am really impressed with them too.

Dad has a Miller 250, and he was shocked at how well the little 135 did when I tested it for the first time in front of him. We all knew it wouldn't be a great choice for 1/4" plate, but for light work like my floor pan, or even 1/8" tubing it's a great little welder. If I can just get the hang of it soon, but in time I know things will improve. it's a lot better welder than I am a weldor.

[bvweld]

Another trick that helps on thin gauge is welding forehand. If your welding right handed go right to left. Changing polarity helps too, (Electrode -) but you really shouldn't have to change it with a small MIG. Keep practicing, you will get there.

[wojeepster]

In replacing panels I make sure the panel is level (butt weld) and then spot every inch. Then I go back and spot in between each inch spot so you now have a spot every half inch, then stich each spot together. That is what works for me.

[dstaley]

I've been getting a lot of practice now between the floor pan, toe panel, patching the transmission tunnel from old shifter cable holes, and closing up all the firewall A/C holes.

You're right, it has to be pretty much a continuous bead of tiny spot welds with the MIG. I've learned that I have to let it cool several seconds between spots, or just move around the patch so that any spot gets plenty of time to cool between little zaps.

Help from you guys has really made all the difference. Thanks!