Waaaaaay too many variables to say it's X% weaker or whatever. Every time weaving comes up on the forum some/all of the reasons why it's a poor technique in most situations get explained. For starters the weld will be more prone to LOF (lack of fusion) defects and LOF at the root makes a MASSIVE difference to the "strength" of fillet welds. While LOF may be fixable (with practice and by macro etching a bunch of test welds) the "pretty" weaved weld will still have a higher input than doing it properly which can have all sorts of metallurgical downsides and make distortion more of an issueI have heard all the arguments against this type of "decorative" weld and I am not swayed by them.
Can someone put some numbers against these "weak" welds? How much weaker are they than a like-for-like normal uglier weld?
Lets ignore of all that and pretend that a tensile test shows the weaved weld is as "strong" as a conventional weld. In the real world parts don't fail because they weren't "strong" enough unless someone reeeeaaaaaally screwed up. They fail from fatigue. Every single one of those exaggerated "dimes" (whether the result of 'drawing the letter e repeatedly' with a MIG gun or exaggerated movements with TIG) is a massive stress riser for a crack to propagate from
Look at any world class motorsport fabrication and you won't see this sort of weld (whether manually pulsed or weaved) for example a BTCC roll cage pic (origional url https://btcctechnical.files.wordpress.com/2012/02/photo-2-roll-cage-installation3.jpg)
with the possible exception of the odd bit of sub 1mm sheetmetal where it may be manually pulsed for the same reasons as done when patching up a rotten car. Grass roots motorsport, especially on the internet, is more often about appearance than science, the colour of welds indicate quality and the size of the HAZ and the attitude is more often one of "parts break"
Looks are a subjective thing, Septics especially often have an odd take on the subject* and often place appearance over everything else. Even when things like "strength" or fatigue life don't matter the silly weaves still lose everywhere else; the whole point of MIG is that it's a fast, semi automatic process that can deposit more metal in less time so lets slow it down and waste most of the speed advantage while using more wire and gas
* for example grinding away the surface healthy teeth and sticking veneers over them for a "hollywood smile" that to any sane person looks like a badly made (too white, too straight,
That's kinda, sorta how sets with pulse capability work but with an important difference. The arc isn't broken between pulses which is why manually pulsed welds are typically full of crater defects on the surface and would show LOF & inconsistant depth of fusion if sectioned and etched. Machine pulsed TIG welds can have the same flaws when the pulse frequency was set too low for the travel speed i.e. not enough overlap resulting in a series of tacks next to each other instead of overlapping enough to result in a continuous weldBut would using a much higher power setting ie on the point of blowing through with a tack not make up for the lack of continuous weld?