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amps / volts welding ratio
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Posted by: Jon K.
I am attempting to understand the mig welder that we run with our robot.
I can adjust both the volts and the amps on this machine. Lincoln 450 Powerwave.
Right now we are running 20 volts, 300 amps. It is a bit hot. I have been jacking with the amps a bit, but am having trouble finding the sweet spot.
.035 wire, .120" steel
Is there a "magic ratio" of amps to volts?
Posted by: ZOMBIE666
whats wrong with the weld that makes you think your not already in the "sweet spot"? just hot? try dropping down your amps to 120-160, raise the voltage to ~30. also mind the wire speed. ,120 steel is pretty thin, 300 amps seems way to high for that. your not running it in pulse weld mode are you? ive heard these thing dont like thin metal in pulse mode
Posted by: Jon K.
Thanks Zombie;
It turns out to be a funny thing.
The robot uses a program to match the wire speed to the amps / volts. I can't tune the wire speed at all.
We backed the amps down to 200, left the volts at 20, and did not get enough deposit of metal, as the machine turned down the wire speed for me. We could slow the travel speed a bit to match, but do not wish to, as we are running production, and need a fast speed to turn out enough parts.
We have upped the amps back to 250, and are looking a bit better.
I haven't changed the volts yet.
I still have no understanding on what increasing the volts will do to the arc.
This is turning into trial and error, I was really hoping someone could give me a clue.
Bewildered;
Jonny
Posted by: ZOMBIE666
well most MIGs start out around 14 or 15 volts ive seen this simple formula:
14 + (Amps x 0.05)=VOLTS
so by that formula, @ 250 amps you should be running around 26.5 volts
is it a Fanuc?
Posted by: Jon K.
Yes, it is a Fanuc. On old Arcmate Jr.
RG controller.
Lincoln 450 Powerwave.
I am in no way qualified to run this thing, but that has never stopped me from doing anything before. 
Thanx a bunch Zombie!! I will crank up the volts a bit, and report back here!!
Jonny
Posted by: Jaybird
jon,
I have been a bit reluctant to comment, as I have no experience with the robotic migs.
I am curious though...is the stinger set to push or drag? Dragging tends to get a little better penetration.
And what sort of gas are you using? If you are using straight Co2, you way want to try a 75/25 argon/Co2 mix. Or visa versa. I think Co2 welds a bit hot.
When I mig 10ga, I will normally not change the settings from what I was welding 1/4" or bigger carbon steel. But then, I have full control of the weld speed.
I have seen a guy on the web that offers robot welding tutorials and books. May be a good investment. http://www.weldreality.com/eds_training_materials.htm
Posted by: VintageDirt
I don't know the first thing about welding but I'm curious how you can change current and voltage independantly. Doesn't Ohm's law apply to MIG welding?
Posted by: Jaybird
When voltage is constant, amperes is more of a current flow requirement, dependant on the load asked for.
Two 440volt motors could require different amperes depending on the HP rating of the motor and how much power it asks the voltage for.
I think manipulating the amps is simply "asking" for a greater, or lesser, rate of flow at a given voltage.
That's my ignoramous take on the thing. (shrug)
Posted by: matt-itude
well if you push the voltage up it will create the arc with the wire or rod further from the surface. so that is an increase in resistance just bridging the wider gap. so ohms law will automatically apply itself to welding just like you turn the amps up for a hotter weld/more penetration. remember a 12 volt battery may have 600 amps on tap but the voltage isnt high enough to make the connection through your body (thank goodness).
Posted by: motometal
so, the welder is manipulating the wire feed and either V or I regulation to manipulate the other variable (V or I) where you set it.
dumb question: is this AC or DC? If it's AC or even pulse/partially rectified DC the waveform, frequency, etc can also be manipulated
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