when there are enough welds, it stops pulling together to the point of massive warpage.
I am not saying this is the right way to do it, I know first panel we did closed up and we just kept welding. There was alot of grinding, grinding thru weld since the panels were on top of eachother and there was no place left for the weld to go.
Dont have anything fancy, but panel ]v[ panel with v as filler stays flatter and wont separate when ground flat. When its ][ the novice grinds and panel separates.
I consider myself a novice.
To be fair, we are all novices. I try to learn something new with each new job.. If you're not learning, you're sitting still. (why do I hear that in a Ricky Bobby voice?)
First off, it doesn't sound as if you are planishing the welds. If that is the case, it would explain the massive warpage. If you are seeing a separation of the panel (visible joint) after grinding with the panels tight together, then your heat setting is too low. You should have a full penetration weld with each individual weld dot so you have weld proud on both sides, this lets you planish that weld dot by it's lonesome without affecting the rest of the panel. As pointed out elsewhere in this thread (or was it Chris' thread?) a hotter weld will typically get you a flatter weld for less grinding and less pin holes, and controlling the heat the panel actually sees by limiting trigger pull duration, you will actually have less HAZ showing. Just filling in a gap void may take less heat, may give less immediately visible distortion, but the biggie is that it also takes shape away from the panel as it closes tighter, you lose crown. On hoods, roof, etc, that equals oil canning in most cases.. Hey, I get it, a dozen different ways to get to town. I've even modified the way I initially started this "dot welding" method to overcome some issues that arose. But in the grand scheme of things, I respond to countless threads a year on here and other car forums where someone's MIG welding efforts have caused an oil can or a _________ (fill in the blank). In 99% of the cases, following what I have written in this thread resolves it. The process addresses the weld from start to finish, which begins at panel fitment and ends at planishing. It's all part of the weld process. Only focusing on the little bit of distortion that a tight butt weld may give is ignoring all the rest of the concerns, and is a recipe for oil cans.
If what you're doing is working for you, then that's all that matters. But I can't see how you can do that without losing crown or causing a low area. If it's in an area that doesn't rely as heavily on crown to hold the shape, then perhaps oil canning wont be an issue for you. I would also offer, if you're ever in the Southern MD area and want to do some weld practice to try it out firsthand, let me know, I'll be glad to help out. Afterward we can try TIG or even gas fusion welding and show you how enjoyable it is to do less grinding.