making better mig welds

[havik180]

I'm still pretty much a beginner but i have tried just about every type of process . I'm ok at best , I don't feel comfortable doing any kind of structural work but that is where my interest lies (chassis/suspension)

So to some of the more experienced weldors here what are the most common mistakes and/or problems made by beginners ? How can they be corrected ? one problem I have is the bead being too fat and too tall , how can I get around that ? Tips on troubleshooting or technique ?

Thanks
Rich

this is my ultimate goal (pic courtesy of Andy)
http://www.millermotorsports.com/mbo...tachmentid=124

[Arcburn]

That picture looks more like TIG rather than MIG... TIG would be great to use but the learning process would take a long time. If that's MIG than who ever did that weld is VERY skilled because I have never seen any MIG weld like that before, most of the one's I see are smooth no "nickel stacks". My teacher at school has been welding for about 25 years and his MIG welds look smooth but his TIG welds are a different story.

[scott-885]

Those are mig beads and can be had by running in a kinda cursive e pattern.
Heres a link to some good info and pics.
http://www.hobartwelders.com/mboard/...ds+wrinkled%27

[Luna]

this is my ultimate goal (pic courtesy of Andy)
http://www.millermotorsports.com/mbo...tachmentid=124

Everytime I see MIG welds like that I wonder if we should be using MIG as the enchmark of bead appearance rather than TIG

Nice Andy. If anyone has more examples like tha I'd lvoe to see them.

[tigman250]

weld appearance depends greatly on sheilding gas used, i just switched jobs, my previous boss used 95-5 (95% argon 5% oxy) now my new boss uses 75-25 (c 25 or 75% argon 25%co2) now C 25 is what i started Mig welding with as soon as i welded with the 95-5 i said i would never run anything diffrent on MY welders! at the new place there are 3 other employees and i cant change the gas type the c 25 seems to weld so cold compared to the 95-5 the beads are tall and skinny they don't seem to penetrate nearly deep enough. in that pic posted by havik180 thoes are the type of welds i'm used to...not so much the appearance of them but how wetted out even they look and to go from that to the stuff i'm forced to put down now it's almost shamefull

[Arcburn]

Those are mig beads and can be had by running in a kinda cursive e pattern.

Thank you for showing me that! My teacher tells us to just go strait and not to do circles, but now that I have seen the proper way to do it I will have to try it!

[H80N]

Cleanliness & Joint prep

havik180
one area that is often overlooked is Cleanliness of the metal.. even a little bit of mill scale or rust will affect both bead appearence and weld quality.. taking a little bit of extra time and making sure that your metal is shiny will pay off ESPECIALLY in chassis and suspension work where you tend to work with relatively thin cross section material... this is not as important for the guys that are doing the really heavy stuff like rock buckets etc. where they really pump massive amounts of heat into the work.. but on the thinner stuff it is critical... the old myth that mig will weld through rust has caused more crummy welds.. when a few minutes with a grinder could have made a huge difference... I see a fair amount of broken welds on both new and repaired equipment... where the mig weld bead had decent appearance but parted right on top of the mill scale or rust...
the other half of this equation is joint fit up and prep... the tighter the fit up the better... and yes mig will fill voids to make up for poor fitup.. but at a cost.. in tube structures like chassis you want to maintain proper geometry.. proper fixturing will help.. but in general the tighter the joint, the less the weld will pull as it cools and shrinks... there is a whole science/art to this process of building a chassis/spaceframe without having it turn out like a pretzel... am sure there are some good books on it... have some old ones from the 1930's on aircraft welding.. they are excellent.. must be some modern ones (think that the EAA has some)
anywho.. enough of my soapbox... just wanted to give you a little bit of input on the larger picture... and please do not take some of these TV shows as gospel on technique... some of those are scary and an example of exactly how NOT to do stuff...
hope this helps
Heiti

[havik180]

Ok how about technique ? what do you pros or experienced guys do (all positions) ? Zig zag , circles , c's , backtracking (forward , back , forward etc.) ?

[JET]

I use C's when working on thin metal and the cursive e's most of the rest of the time. I am not a pro like some of these guys though.

[Bowtieman31]

Making better welds

one problem I have is the bead being too fat and too tall , how can I get around that ? Tips on troubleshooting or technique ?

Usually the cause of the welds you describe is going too slow. Try speeding up your movement of the torch. You may also try slowing the wire speed down a bit. It's all a matter of practice, practice, practice.....

[Paul Seaman]

This is the technique sesion:

The way to flatten the bead is to move quick accross the center of the weld and hang out longer in the edges. So if you'll follow along here is how I would get there.....Doing NNNNN as a patternat the edge of the bead you'll count one-two, then move quick with a snap accross the center of the weld and count one-two then snap accross the center and keep repeating this action . The count allows the weld to fill the center and keep the bead profile flat and fill in the toes to prevent undercut. Also if your bead looks like stitches when finished you are moving too far foreward on the slanted move foreward.

The 95/5 gas will allow less need for the count and produce flatter welds, but it also makes controlling the puddle harder for out of position work as a novice you'll have a great deal of trouble in the vertical up and overhead welds. The C25 gas is sorta the best balance till you've attained a bit of experience. I run only c25 due to the amount of odd position work I do, and after owning my machine for over 2 years I am still not up to the task of 95/5 in the overhead.