Welder Problems and Aluminum welding.

A friend let me use his Argon bottle, I'll pay him for at least 4X the amount of Argon I use. I washed off the fender, the welds are on the inside
of the fender, there's a little dirt under the fenders... Then I used one of those spongy abrasive stripper/surface conditioning drill wheels, and the final cleaning was by hand with a new SS wire brush. Since I haven't welded with this machine in a long time, I practiced running some beads on scrap aluminum.
So I get the arc started, the aluminum starts looking sweaty, then a bright shiny puddle, added filler and moved the puddle across the scrap. Worked like I remembered..
Then onto the trailer, the weld is a lap joint, I started heating where the metal was doubled, got the base all melty but never got the bright shiny puddle on the surface. Maybe contamination on the surface? Maybe I should have cleaned with solvent such as alcohol or MEK before the SS wire brushing?
But before I got any further, the welder started acting up. It's a Miller 330A/BP and it seems the weld output became unstable. The HF arc gap would go on and off, the weld arc would go on and off, very erratic. I would suspect the HF but I would think the arc would hold even if the HF went out. When I quit welding for a while to check it out, it would start working again for a minute or so after I re-started trying to weld. Would it be likely that a fan in the unit quit working and would shut down from over heating? Just wondering if it was overheating and shutting down like it might if you went over the duty cycle, I wasn't using over about 30% of rated power but if a fan wasn't working it seems it could cause problems. Any ideas what would make the output erratic like that?
I'm ready to get a Syncrowave 250 and sell the 330A/BP for the scrap copper and use my torch, water cooler, and argon flow regulator on the Syncrowave. I've been strongly considering ordering a brand new Syncrowave 250 welder only, found them advertised for $2590 + $7 shipping + Taxes. It would be nice to have the current version with warranty and all. I have found no stores in the area that stock them but they say they can get them in a couple of days.
RogerN
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On 08/08/2010 03:23 AM, RogerN wrote:

Could be contamination. Could be that the aluminum alloy that the fender is made from is not weldable. Cleaning with lacquer thinner or acetone on both sides of the weld would be a good idea.

Assuming that you are welding with AC (as you should be on aluminum) if the HF goes out, the arc may or may not restart as the voltage passes through zero volts each half cycle. I would check and clean the spark gap points on the HF generation part of your machine. There are some high voltage capacitors that fail in the HF section on old machines, but they are not as easy to deal with.
Bob
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Back when I was welding aluminum, I had two encyclopedic books, which have gotten away from me over the years. One I got in welding school, and just wish I could get the name of it because I'd get another, and it was great.
But in it, there was a listing of the various aluminum alloys and their compatible rods. It was complex. Pure aluminum is not used in many things. Therefore, you have to get a rod that is compatible with whatever base alloy you have. Now, identifying that alloy is the problem. Sometimes nothing short of a very expensive spectrometer will give you the number of the alloy. There are guides that list "compatible" rods to base metals, but getting it exactly right is a shot in the dark.
Sorry I'm not much help, but I didn't have a lot of experience (or luck) in welding aluminum. With aluminum, you can have just one variable wrong in the equation, and it is unforgiving.
Steve
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The original welds looked like they were made with a spool gun and the fender only had maybe 6ea 1" welds holding for a tandem axle fender. Since if was welded from the factory I'm guessing it's weldable aluminum.

I re-gapped the points last night after it started having problems, same thing, worked great for a few minutes and started acting up again. I was suspecting capacitors just because I know they don't last as long as many other electronic components, if I can find them and they are affordable I'll replace them just to have the old caps eliminated.
My first few practice welds did great, or at least the welders part did great, good clean puddle. I never had problems with the HF before on this machine, I did a little reading up in the manual and will take a better look at the points.
RogerN
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You may be right, Roger..it is entirerly possible that its capacitors. Something to check however..is its performance on DC as well as AC. One will use caps..the other is less likely to do so.
Gunner
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Sounds like its time to clean up and readjust your contacts for the HF section of your welder.
Check for a small port or covered control that when you open it..will give you acess to the vibrating points.
Here is the link for the manuals ...you can download and follow the directions.
http://www.millerwelds.com/service/ownersmanuals.php
AC tig needs full time HF
Gunner
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wrote:

There are points with arcing between them, it started off working good but became erratic after welding a while.
My owners manual says there is a fan, when I switch the machine ON I hardly hear any sound at all, should the fan run continuous? I found a thread from 2007 where Ernie said the HF transformers would get weak on these old machines, I'm wondering if that is going on. Whatever it is, HF worked fine and then became very erratic after about an hour of attempted welding. I plan to head back and try again today.
I adjusted the points within their stated range of .004 to .013 (.010 nominal), the shim I used measured about .012 so my gap is toward the wide end.
I'm trying to get the trailer ready to go and trying not to get sidetracked too much, first no argon, next welder problems, heck, I have enough problems just welding aluminum without other problems. I can weld the aluminum if I get a clean puddle before the base melts but that doesn't always happen for some reason.
RogerN
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