I'm having some troubles when welding upside down (or atleast at an upward angle)

Basically the molten wire turns into a little ball that gets closer back to the tip of the torch and it's difficult to get the melting done at the metal that needs to be welded

Any tips on how to prevent that?

Oh... this is on a MIG-welder with gas

reverse the polarity of the leads.

huh? how does that work?

It’s a tough one to explain, but try turning down your wire speed a little, and move along quickly enough that you don’t build up a big pool of molten metal. This is where it’s extra important to watch your puddle and walk it along at the perfect speed, not too fast, not too slow.

The arc travels from negative to positive, so if you have it set for electrode positive, you will put more heat into the electrode, and less into the work. While electrode negative, more heat goes into the work.

When upside down, if you are set for electrode positive, your wire will tend to melt faster and create the problem you are describing. The down side is that if more heat is going into the work, you have to be extra careful to control the more molten puddle. Dial the power down a little if it becomes an issue.

ok... I'll check the welder's manual

can I leave it at that setting, or should I go back for "normal" welding?

thanks for the tips!

So far for me, not building up big blobs is the hard part. It's also a lot harder to get good penetration than I expected. I just butt welded a pair of things made of 18g sheet, and had to turn the power up most of the way (110v MIG) to get good "stickage". Redid the welds about three times before I got it. The first two times, I just made big blobs that were barely stuck to the parts.

Wire speed and hand speed seem to be very closely related. I presume moving your hand slower helps in penetration (?), as does higher power, but also increases the chance of burning through (which is actually a far smaller risk than I first assumed).

I haven't tried upside down yet, but I have worked on a vertical surface, and didn't really find it any different from working on a horizontal surface.

The key to welding is puddle control. You need to build a puddle, and walk it along at the proper pace to achieve the desired weld. Hand speed, and wire speed are all dictated by the puddle. If you have really high wire speed and thin material, you'll be moving very quickly. That's a good way to minimize warpage, but control is not as good.

Also, a lot depends on whether pushing or pulling the puddle. Pushing will not penetrate as much and will drive the puddle, where with pulling, you are allowing the puddle more time to penetrate.

I'm still working on my welding skills (I get along, but could still use improvement)
I've found the hand/eye coordination is just as important as your welder settings
Keep it in one place to get a nice puddle forming and just a fraction before you blow throught the metal, move a little further

I think that's part of the problem. I never see the puddle, just the blob. Perhaps I need to reverse the polarity on my leads, too.

Ah, I like negative setting with flux core. It goes on like flowing water in any position.

I can never weld one handed. I alway hold the tip with my left hand to keep it steady.

me too
an auto darkning helmet sure helps a lot too

I usually start by turning down my wire speed, and leaving everything else alone if the pen' is good. I adjust from there, but not too often.

I welded my Mayeur stiffening kit on last winter and it involved alot of upside down welding. After experimenting a bit I found what worked for me was to turn the heat and the wire speed up and do a series of 'spot' welds right beside each other. You don't have the trigger pressed long enough to form a molten ball, but the increased wire speed and heat will give you a nice, deep 'spot' weld. Attach a bunch of them together and you get a decent weld that isn't too ugly. I also think this method avoids some warpage because the amount of heat put into the metal isn't as intense.

I love hearing welding tips from people. And Jeroen, it's nice to hear that you're working (actively) on your car!

Practice practice practice. Then practice some more.

If you want to learn how to use your MIG welder and you must teach yourself (because you don't have any professional welder neighbors to show you), get yourself some 1/4" plates and turn the heat up all the way and go to town welding 1/4" plates together. On the highest temperature setting, adjust the wire feed in small steps to see what happens.

You will see that with a higher wire feed, your welds will stand taller and can approach looking like a caterpillar crawling along. As you slow the wire down, the weld is hotter and you get more penetration and the base material will acually fuse into the weld.

If you slow the wire down too much, you just vaporize the wire and it will stick in the nozzle tip.

You must also practice holding the nozzle tip consistantly. I like to try to keep the tip away from the base material far enough to have about 1/4" of wire sticking out of the tip. As you get the nozzle closer, the weld can get hotter, but you run the risk of melting the wire to the nozzle tip. If you move the tip further away, the weld cools off and you get a more blobby weld.

It takes practice.

When you get good at welding 1/4" plate and you know how a good weld "sounds" then you can move to thinner materials. The thinner materials do exactly what the thicker materials do, but with less heat. At maximum heat, you will 'blow-through' thin sheet metal until you figure out what wire speeds you need to use.

I know that on my welder, I can weld sheet metal (car bodies) on 2 different heat settings (but with two different wire feed speeds). If I go hotter, I speed up the wire. If I go with the lower heat setting, I slow the wire down. To prevent warpage, I use the lower heat setting. If I want strength and lots of penetration, and warpage is not a concern, I will go hotter.

The hotter the weld setting, the easier it is to get good penetration and a nice looking weld, but the price of using more heat is warpage and possibly overheating the metal causing it to turn brittle.

You don't need to reverse the polarity to do well upside down. Use a higher wire speed and slightly lower heat. Also you have to keep the tip closer to the work This will keep the arc short and the extra force will help push the puddle up. As Steve mentioned pushing the wire ahead of you instead of pulling it behind will cause less penetration which will help. You can use short bursts that melt a single puddle, then repeat over and over, allowing each puddle to solidify before pulling the trigger again. This technique requires higher heat than running a continuous bead but helps prevent burn-through. Last tip, wear leather.