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Posted by Bob La Londe on July 28, 2008, 3:05 pm
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Practicing corner joints and T joints.
Ok... Welding misc thin aluminum sheet (upto about 10 or 12 gauge) I can
pretty much go right off the settings on the card on my Miller 212 and
adjust for thickness... except, if I start right at the end and weld all the
way to the other end I melt the stock at the start and end. Worse at the
end. If I start 1/4 to 1/2 inch from the end and stop about 1/2 inch from
the end I get a nice neat weld. Then I can wait for it to cool and go back
and do tiny little micro burns to finish up the ends of the joint. Seems to
me that would leave a lot of room for a bad weld in that little stretch at
each end.
Is that the best way to do it?
If I used some kind of backing at the joint would that work out better or
would the backing material just contaminate the weld?
I'm still playing with scraps and drops, but I have started doing some
material layout planning for my first boat repair project.
Bob La Londe
www.YumaBassMan.com
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Posted by Curt Welch on July 29, 2008, 2:23 pm
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> A paint marker on the metal as a guide might be a good idea too so I have
> a good idea where to speed up and slow down.
That sounds like something worth trying. I never heard of that.
Aluminum is just so damn tricky because it doesn't change color like steel
to make it easy to see how hot it's getting. It goes from normal, to
slight sag, to big gaping hole in your project in about .1 seconds. :)
> That will be tricky though.
> I am already moving about as fast as I can and still keep the gun pointed
> in the right general direction to make decent welds.
Yeah, MIG is really great when you have to do large sections fast. But I
never really did get it down for thin aluminum. It really did feel like
you had to get up a running start and point the gun at the weld as you ran
past because it was so damn fast. Trying to go slightly slower or slightly
faster was almost absurd because you were moving the gun so fast to start
with it was hard to get any sense of how fast you were really going. I was
doing this with a Miller 251 with a large spool gun and 030 wire. Maybe a
smaller MIG unit with smaller wire would make it easier? Do they make
smaller wire than 030 for aluminum or does it just get impossible to feed
when smaller than that?
If you had to do the same weld, every day, with the same material, and the
same welder, I could understand how someone could master MIG on thin
aluminum. Otherwise, I'd just use the very slow TIG if I had to make a
good weld.
A 4 inch mig weld was maybe 1 second of welding. A 4 inch tig weld would
be maybe 20 seconds. (haven't timed it and that might be off but that
sounds about right).
> I want to tackle some projects that will take some long continuous welds
> (several feet at a time) and I figured the MIG would be a lot faster.
Yeah, it surely would. If you can master the weld, that's the way to go
for speed.
> Besides I wanted the MIG for welding steel also.
Me too. :) Still trying to figure out how to justify buying it. :) The
fact that it could do aluminum is nice as well.
> I have a Chinese flux
> core from Harbor Freight (hence my references to the "china welder"), and
> I have pushed it to and beyond its limits for steel welding.
>
> I have been looking at a TIG for small spot repairs, hole filling, etc,
> but right now I haven't enough cash and honey do points to get away with
> it.
Yeah, building small robots is one of my desired goals and being able to
work with aluminum to save weight and battery power is a big win for that.
Because of the small size of the projects and the fact it's just hobby work
I don't need to make a profit on, the slowness of TIG wouldn't be an issue
for me. So for that, I'd like to get TIG (and would end up with Stick as
well at the same time). But I'm looking at the $3K range machines for that
and can't justify the money yet for the same sorts of reasons you mention.
In the short term, I'm looking at MIG mostly for small steel projects
because MIG is just so easy and fast and fun for sticking stuff together.
There are a lot of little projects I'd like to be able to do that I can't
currently do because I have no welding equipment yet.
And, MIG gives me the option to do some aluminum work for an extra $200 or
so for a spool gun without having to wait until I can justify the TIG
machine. So that too is a win.
I've looked at the harbor freight stuff multiple times just to give me
something to use for now like you have done, but I keep telling myself it
will be better to wait and buy something bigger and better that I won't
outgrow so quickly.
> You know, your reply had a lot of good information and ideas to make me
> think about. I had to read it a couple times to get everything out of
> it.
I hope it's of some help. Good luck...
> Bob La Londe
> www.YumaBassMan.com
--
Curt Welch http://CurtWelch.Com/
curt@kcwc.com http://NewsReader.Com/
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Posted by Bob La Londe on July 29, 2008, 6:52 pm
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> Yeah, MIG is really great when you have to do large sections fast. But I
> never really did get it down for thin aluminum. It really did feel like
> you had to get up a running start and point the gun at the weld as you ran
> past because it was so damn fast. Trying to go slightly slower or
> slightly
> faster was almost absurd because you were moving the gun so fast to start
> with it was hard to get any sense of how fast you were really going. I
> was
> doing this with a Miller 251 with a large spool gun and 030 wire. Maybe a
> smaller MIG unit with smaller wire would make it easier? Do they make
> smaller wire than 030 for aluminum or does it just get impossible to feed
> when smaller than that?
I would think you could go slower with a larger wire. I have been playing
with .030 4043, but I also have a spool of .035 5356 for when I get serial
with it.
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Posted by Curt Welch on July 30, 2008, 11:38 am
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> > Yeah, MIG is really great when you have to do large sections fast. But
> > I never really did get it down for thin aluminum. It really did feel
> > like you had to get up a running start and point the gun at the weld as
> > you ran past because it was so damn fast. Trying to go slightly slower
> > or slightly
> > faster was almost absurd because you were moving the gun so fast to
> > start with it was hard to get any sense of how fast you were really
> > going. I was
> > doing this with a Miller 251 with a large spool gun and 030 wire.
> > Maybe a smaller MIG unit with smaller wire would make it easier? Do
> > they make smaller wire than 030 for aluminum or does it just get
> > impossible to feed when smaller than that?
>
> I would think you could go slower with a larger wire. I have been
> playing with .030 4043, but I also have a spool of .035 5356 for when I
> get serial with it.
For thicker wire, but the same size work material, you would feed the wire
slower, but I think you would tend to weld (travel speed) faster. It would
depend on actual the settings you used.
The thicker wire takes more amps to melt and as a result, puts more heat
(and metal) into your weld quicker. For short circuit mode, if you set the
volts and wire speed to get the same "buzzing" rate (say 200 contacts per
second), each "buzz" melts back a chunk of wire. With the thicker wire, it
takes more energy to melt it back for each "buzz". The result is more heat
and wire into your weld as the wire size gets thicker for each "buzz" and
for each second of welding (200 contacts).
You can slow down the feed for either size wire, but for a constant buzz
rate, you will always get more heat and wire with the thicker wire. The
optimal setting for each wire size will likewise give you more heat and
material per second with the thicker wire, meaning you have to go faster to
keep it from burning through or depositing too much metal.
The smaller wire allows you to weld slower. Think of what it would be like
welding with thread sized wire for example. You would have to hold it on
the same spot for a long time to get enough metal and heat to build up.
And if the thread was too thin, it wouldn't even be able to transfer heat
fast enough to your weld unless it was feeding like a bat out of hell.
And think of what it would be like to weld with 1/4" wire on 1" plate.
Each "pop" from the burn back after contact would transfer a ton of heat
into the plate.
But hey, I just now ordered myself a mig welder so I'll finally be able to
do welding projects at home now!
--
Curt Welch http://CurtWelch.Com/
curt@kcwc.com http://NewsReader.Com/
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Posted by Bob La Londe on July 30, 2008, 1:04 pm
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> For thicker wire, but the same size work material, you would feed the wire
> slower, but I think you would tend to weld (travel speed) faster. It
> would
> depend on actual the settings you used.
Makes sense when I think it through.
> You can slow down the feed for either size wire, but for a constant buzz
> rate, you will always get more heat and wire with the thicker wire. The
> optimal setting for each wire size will likewise give you more heat and
> material per second with the thicker wire, meaning you have to go faster
> to
> keep it from burning through or depositing too much metal.
Which makes me think of another thing. I have been practicing with 4043
.030. I bought it mostly to play with. I have a spool of 5356 .035 which I
bought just for my first marine project. If this logic follows through when
I switch over to the thicker wire for the thin stuff I plan to weld I'll
have more problems with it, and perhaps I should order a spool of .030 or
even smaller if available in the 5356.
Dang it dude. Give me 20 or 30 years and I just might get this stuff
figured out. LOL.
Bob La Londe
www.YumaBassMan.com
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> a good idea where to speed up and slow down.