OK you guys, I owe you an apology. I re-read this thread just now, and after reading it today, I have no idea how I read what thought I read yesterday. What I read (or misread) somehow in my mind got taken totally out of context. So again, I apologize for my comments. Today I see that they were totally out of line with what was posted.
I don't know what else to say.
Let's move on, OK?
Or, beat me more if you must...
The difference in welding with AC and DC is not such a fine distinction as to not be noticed by an observant person. The characteristics ARE NOT THE SAME.
Exactly what I said earlier. The arc characteristics are different, but overall, the end results are similar. I did not say exactly the same, but similar.
Lets conduct a little poll and maybe learn something... Do we have any technically trained professional welders here? If not, do we have folks with access to same?
Yes, my father is a professionally trained welder. He taught me how to weld many many moons ago. I still frequently ask him for advice on making two pieces of metal stick together.
Given the availability of a welding machine that can provide either AC or DC, when and how often do they select AC over DC and why?
With the SMAW (stick) process, AC is
almost never selected over DC when welding if DC is available. One exception is when stick welding Aluminum. That must be done with AC. Another time when AC would be selected over DC is when an output higher than the DC capability of the welding machine is required, as I stated in a previous post. Another time when AC is selected over DC is when arc blow is encountered while welding with DC current. Susceptibility to arc blow is a distinct disadvantage to welding with DC current. If you're not familiar with arc blow, I can explain it for you...
Why grind on this issue? Someone asked for help/advice. If DC is as I suspect, better in most instances than AC, then good advice would be to go the extra expense and get a buzz box that also supplies DC. If in certain instances AC is to be preferred then the guy will be prepared as the welder will offer both AC and DC. This is not to say that AC doesn't weld OK but what if DC is better enough of the time to warrant the extra cost? Then it is better to advise the guy to go AC/DC.
Let me dig out and quote from "
Welding Essentials, Questions and Answers, Expanded First Edition". It says it all better than I can...
"In general, which is better to weld with, AC or DC power?
DC almost always provides the most stable arc, and more even metal transfer than AC. Once struck, the DC arc remains continuous. When welding with AC, the arc extinguishes and restrikes 120 times per second as the current and voltage reverses direction. A DC arc has good wetting action of the molten weld metal and uniform weld bead size at low welding currents. For this reason it is excellent for welding thin sections. DC is preferred to AC on overhead and vertical welding jobs because of its shorter arc. Sometimes arc blow is a serious problem, and the only solution may be to switch to AC. Most combination electrodes which are designed for AC or DC operation work better on DC."
"Are there any advantages in SMAW to using an AC arc over a DC arc?
There are no particular advantages to using AC over DC in the SMAW process, except the lower cost of an AC welding power supply and a possible way to get around arc blow. Equipment cost aside, AC has no great advantages."
That's what the book says. I'd liken it to an economy car vs. a luxury car. Both will get you to where you are going, but one is nicer to drive than the other. AC will get the job done, but DC gets it done better. I hate to state it like that, because it really makes AC sound worse than it really is. AC isn't that bad at all. DC is just better. Is DC that much better to pay nearly double the price for an AC/DC machine vs. a straight AC machine? It depends on who's buying the machine. I decided it was, and bought an AC/DC machine. My Dad says that if the money is coming out of his wallet, it isn't. He's the professional welder. He says you can still do anything with AC that you can do with DC... DC is just nicer to weld with... more of a "luxury", not a necessity. And, he says that he doesn't weld enough away from work to justify the added expense of AC/DC when AC alone will get the job done.
Food for thought... If DC isn't needed or useful then why supply buzz boxes that are AC/DC? Why would folks pay more to get a feature that is inferior to the AC only machine which is cheaper? So is there a conspiracy among all the major manufacturers of buzz boxes to hoodwink the public into buying "bogus" extra cost features that perform worse than the cheap version? Probably not. Most likely DC offers utility worth the difference or the units wouldn't sell.
See above... Chevy vs. Cadillac basically. DC isn't inferior to AC... but it's an expensive option...
