907
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| posted on 25/2/06 at 10:27 AM |
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Setting up a MIG
Hi All,
Firstly I must point out that I don't own, or have never used a single phase Mig from,
how can I put this, the cheap end of the market, so I may not understand the problems
involved in setting one up, so feel free to ignore anything I say.
A successful setting, (that sound of frying bacon), is a question of a perfect balance between volts and wire speed.
Every welding machine is different but you may have a rotary switch (say 1 to 10) for wire speed, and another rotary
switch or stepped settings, (hi/lo 1 2 3 4) for volts.
Wire speed = amps
Volts = power
Too high a wire speed and it will feel as if the torch is being pushed away from the metal.
Too high on the volts and the arc gap will be to long, to the point when it will burn back to the tip.
To set up...
select a voltage setting, say 75% (if you have 1 to 4, then No3)
Set the wire feed at 75% (if you have 1 to10, then 7.5)
Try it, then turn the wire up and down and find that middle position where the sound is a nice even crackle, (frying bacon)
You've now found a setting for a given thickness of metal. On a 180amp machine this might be, say, 4mm to 4mm.
On a small machine this might be 16g to 16g.
Repeat, starting with a lower voltage setting, then again with a higher one.
Try to end up with a range of settings for your machine that will cope with a range of thicknesses.
Your test welds will have to be on suitable thickness plate. You won't find a setting for 3mm by trying it on 1.5,
just blow a load of holes.
So you now have a range of settings, say 4 or 5 to try out on various thickness metal.
Tips.
When you find a good setting write it on a piece of masking tape and stick it on the side of the welder.
A setting higher for vertical down, a setting lower for vertical up.
Try not to alter two things at once.
Only pull the torch when going v/down, all other welds push it.
Thick to thin, play the arc on the thickest metal, the pool will flow onto the thin side.
If your welder is on the limit, then set the job up so you weld uphill at 45deg. It will aid penetration.
A machine that will weld 6mm plate will weld 10mm vertical up.
Hope this helps someone.
Paul G
ps. gas mix is argon / CO2 (not argon / oxy) sorry
pps. I assume your welding equipment is in good condition. If not this is all a waste of time.
[Edited on 25/2/06 by 907]
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Syd Bridge
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| posted on 25/2/06 at 11:00 AM |
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Something often overlooked, but some have mentioned, is the EARTH and the quality of the earth connection and its significance.
The old fella who taught me would NEVER trust one of those spring clamp things. I saw him cut one off the end of a new earth lead, cut back the
insulation, and use a G clamp to secure the earth.
This gives a bigger earth area, and a much more secure connection. He showed me the difference between the two methods, and there was definitely no
argument as to which sounded better as he welded, and looked better as a result.
When the end gets straggly, just cut back and you have a nice new earth connection! The people he was working for were forever at him for doing this,
but there was no doubt that he produced the best work of anyone in the 'shop.
To watch this man weld paper thin titanium in a fish tank was akin to watching a fine artist at work!
Just something else to think about. 
Syd.
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ERP
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| posted on 25/2/06 at 06:27 PM |
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This topic is extremly interesting.
I've just started welding too, and my trial and a lot of error seems to point to the fact that there are basically 3 variables involved.
Voltage, feed speed and distance the welder is from the material and speed which you mive the nozzle.
I started by setting everything on 50% or so, and destroyed 3 tips in a row before I realiased that the first 5 settings on my welder were pulse
settings, so I actually had the wire feed on minimum <doh>
With some practice I managed to run a few OK looking beads on a piece of plate, then tried doing the same on different thicknesses at 90 degrees to
eachother and had all the same problems all over again.
I can get the frying bacon sound at a massive range of voltages sat 3 through 7, but I fee rushed at the higher settings, so I've been turning
the volts and the feed down, and doing things more slowly. Is this the right approach?
My welds don't look completly horrible, a bit too much material, and I seem to be getting OK penetration.
I'm using 75% argon 25% CO2 as a shielding gas, I just set it at about 17psi and haven't touched it since. Is there a rule of thumb about
gas pressure?
[Edited on 25/2/06 by ERP]
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Mr G
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| posted on 28/2/06 at 06:52 PM |
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Good info and diagrams of weave techniques etc:
HERE
Cheers
G
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NS Dev
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| posted on 28/2/06 at 07:26 PM |
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quote:
Originally posted by ERP
I can get the frying bacon sound at a massive range of voltages sat 3 through 7, but I fee rushed at the higher settings, so I've been turning
the volts and the feed down, and doing things more slowly. Is this the right approach?
[Edited on 25/2/06 by ERP]
Yep, that is EXACTLY the right approach! You should avoid ever feeling rushed during the weld, that's when the results will take a sharp turn
for the worse.
The gas pressure you mention does sound high, unfortunately I have no idea what it should be! I have no gauge or flowmeter, I set it by the
hiss/whooshing noise, and just know what it "right" by the sound! (I just use an old pub regulator that adjusts with an allen key, was a
temporary fix that has now done 6 years!!!!lol )
Retro RWD is the way forward...........automotive fabrication, car restoration, sheetmetal work, engine conversion
retro car restoration and tuning
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NS Dev
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| posted on 28/2/06 at 07:27 PM |
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PS apologies for my rather strange post further up, I believe I was rather under the influence when that was "written" 
Retro RWD is the way forward...........automotive fabrication, car restoration, sheetmetal work, engine conversion
retro car restoration and tuning
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JC
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| posted on 2/3/06 at 08:10 PM |
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Tried all the things suggested the other night. On a test piece I managed gorgeous welds but when i went to the 'real' thing, much better
but not as neat, although a more experienced welder sade that they looked plenty strong enough. I found that with the wire feed set to
'2', the wire disintegrated when it touched the weld pool, forming a blob on the end of the wire. The wire then fed down, touched the
weld pool and the same happened. With the feed on '2 and a tiny bit' it seemed a bit fast. I also found that one weld would be really
nice, then without altering anything, the next would not go so well. Ahhh the joys of self-building!!!! 
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907
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| posted on 2/3/06 at 08:49 PM |
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It's soooo hard to diagnose what someone is doing wrong when your the other end of a pooter.
Are you trying to weld with too long a wire extension.
Get in close. The shroud should almost touch the weld as you progress.
If your liner or tip is restricting the wire feed rate this will have the effect of high volts / low wire.
When you move position to go from test piece to job you may be twisting the lead, making the
wire speed lower. Keep the lead as straight as you can.
The test is to disconnect the earth, (so you don't get a shock) and hold the wire as it comes out
of the tip between thumb and forefinger, pull the trigger, then squeeze the wire. I you can stop it
with ease and make the feed wheels slip, or stop the motor, then somethings wrong.
Try this with the lead out straight and again with it bent, as it would be while welding.
I may be way off here, but it would explain why one weld is OK, the next one poo.
Paul G
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