Welding Advice

[MP&C]

First, I'll be the last person to say this is the right way, the only way, etc. As the more correct way would not involve a Mig
It works for me, and has helped others. If you have a method that works, then by all means use it and share it. Let people see it and try it, they can have options..

Part of the methods I describe from fit-up to final weld dressing is all in an attempt to maintain consistency throughout. I do the planish first as it seems to better negate the shrink that pulled from all directions by stretching in all directions. Then grinding it down gets it out of the way for planishing the next (overlapped) weld.

All of us have seen distortion in the panel from welding. Even when using a tig, you will see some distortion, but regardless of the process, it is most notable on any areas of CHANGE. A start, short weld pass, and a stop, will show a different HAZ at the ends than it does in the middle of the "weld pass". Feeling the panel after cooling, you can also detect a slight ripple at these changes. Welding sheet metal with a Mig is one of the worst methods going, based primarily on all the cleanup work it entails. The best going is a no-gap, no-filler fusion weld using either Tig or O/A. The fusion weld also limits the distortion as the starts and stops are at the ends only, and HAZ between is about as consistent as you can get, from consistent heat and not stopping...

So yes, even though the "dot" method takes a bit of time, it's intent is to provide a full penetrating weld each and every time, and promote consistency in weld size and thus HAZ size. On a lengthy weld there will be a number of welds tacked in place, preferably spaced evenly, where once you get done with the last weld, the first should be cool. Same effect with grinding. So there is a somewhat "assembly line" to the process, it's not like we're only working one weld at a time, start to finish. The initial planishing should remove any shrinking issues. A short burst of a weld pass is not the end of the world, but I'd venture to say that from start to finish the weld size will be difficult to maintain in sizing and weld penetration consistency. Any larger welds or larger areas on weld passes will affect both HAZ and distortion.

So as you can see, the process is done to promote an almost OCD effect of welding dots all the same, planishing all the same, overlapping all the same, etc. Even though Mig is the worst process to use, the methods to my madness are an attempt to bring more consistency to the processes throughout, for more consistency in straightening the panel out in the end, for HOPEFULLY less filler needed. And again, if someone has a method that works, by all means, use what you're comfortable with.