Weave VS Stringers VS manipulating the electrode (My opinion)
When I weld in the vertical position with GMAW or FCAW I have to manipulate the electrode. Even if I am making a 3/16" fillet. This manipulation reduces the convexity of the bead by spreading the heat out from the arc and depositing metal over a less concentrated area.
As an inspector for a steel fabricator in the past I was involved in monitoring the welders techniques in some cases. In ALL cases in which the vertical fillet welds being made showed excess convexity or overlap, the welder was just putting the electrode in the corner and welding uphill.
This effect can be noticed very easily by making a verical fillet weld using GMAW on maybe 2 pcs of 3/16" thick material. Using about 17.5 to 19 volts and some .035 wire adjust the wirefeed speed to your liking. Then make a vertical fillet weld without any manipulation OR triggering the gun.
is an example of weaving.
Then try one with slight manipulation < 1/16" to each side of center. Do the weaving very rapidly but with a distinct pause on each side. The pause does not have to be visible, just enough to feel it in your hands. Also do the pause with enough frequency that you are keeping most of the puddle molten.
Then see if there is a difference in bead appearance.
That is one type of "weaving". Here are some thoughts I have on that type of weaving.
1) welds that are out of position are affected by gravity while they are molten.
2) welds that freeze faster are less affected.
3) if the arc were to stay in the moddle of the puddle, the energy heat must 1st go through the molten weld metal before it is transferred away by the bas metal. If that is the case, the puddle stays molten longer and has more time to be affected by gravity.
4) the weld metal is going to be molten no matter HOW you manipulate the electrode.
5) slight manipulation of the electrode will help spread the heat to the base metal more evenly.
6) spreading the heat out slightly will help "wet the edges" of the puddle.
7) spreading the heat out will reduce the amount of time the center of the bead is hot.
8) for a given size fillet weld or volume of weld per inch, manipulating the electrode has NO effect on heat input if the parameters are the same.
9) all of this is my opinion.
The weave vs striger debate has gone on for a long time. Each has its place. In my 28 years of welding I have always manipulated the electrode when welding vertical. even if GTAW of 1/8" fillets.
However to just randomly weave the electrode from side to side creating a large wide puddle is not suggested. Each joint, base metal, filler metal etc. may need its own techiques. A weave bead fills the joint at the EXACT same rate as stringers. As travel speed slows down, the amount of heat going into the base metal goes up. In some metals this can cause problems that can not be found by inspection after welding.
Regradless of what method you use, be sure that the weld metal and base metal are fusing together. With multipass welds using stringers, the bead profile and placement becomes an issue. With weaving the visible bead contour may be able to be better controlled however the underlying fusion may be a problem if not done properly.
All of the above is just one welders opinion. You can be sure to find many more. There are more details I have floating around in my head but I better stop.