Mig welder CV settings, voltage?

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Okay i am a bit confused.  If you take a simple standard mig welder you have a knob for the main power setting that will have numbers or letters ie. 1,2,3,4 or a,b,c,d etc.  This is called the voltage adjustment, right?When you look at a circuit diagram, that big switch will correspond to the different taps on the transformer to let in more or less voltage.Now, you have the wire spped knob.   But my confusion is this.  When you fiddle with the wire feed speed and bring the wire closer or further away this will either give you a smaller arc voltage or a larger arc voltage, right?So then in that case, both the knobs on the welder only really control the voltage?Then also the voltage will change depending on how close you hold the gun to th weld?
Reply:the voltage taps control the voltage. It remains constant no matter the stick out or wire feed speed. The second knob that changes the WFS changes the current.  The faster the speed the higher the current. If you stick weld the current stays constant but varying the arc length varies the voltage
Reply:Would it have not made senses then instead of having 12 3 4 or a b c d that it was labeled as say 17.0v, 17.5v 18.0v etc etc?So that means that say on 17volts i would have an operation amp range of???  Then for 18 volts, 19 volts etc you can workout or estimate an amperage range?
Reply:And regardless of what setting main voltage setting you are on, as you adjust the wire speed the arc gets smaller or larger.  But the voltage does not change?  I say this because on the plasma cutting tables a larger arc registers as a higher voltage and vice versa.  But maybe a plasma power source is not CV and is then different to the migs?
Reply:Hey Peter,You can check the shop manual for whatever unit you have &, generally, there is a chart that shows tap(1,2,3,4/a,b,c,d) voltages. Here is what I did......Denny Attached ImagesComplete Welding/Machine/Fab. ShopMobile UnitFinally retired*Moderator*"A man's word is his honor...without honor there is nothing.""Words are like bullets.... Once they leave your muzzle, you cannot get them back."
Reply:Good idea Denny, SO I think it says 20 23 25 26v?What if you want 22volts then? or any value that is not on the switch position?
Reply:On a MIG unit with voltage taps, as you increase the wire speed (amperage), the load voltage that the tap outputs decreases.The above is also true for certain variable voltage unit.Last edited by Dan; 10-05-2011 at 10:44 AM.ESAB Migmaster 250 Hobart Ironman 230Multimatic 215TWECO Fabricator 181i & 211iHH125EZ - nice little fluxcore only unitMaxstar 150 STH - very nice
Reply:Hey Peter,The older MIG's were individual tapped units & the voltage outputs are fixed. Some of the newer units have a continuous voltage adjustment & can be quite varying. I don't have any problems with fixed taps as I adjust the amperage with the WF dial. You can simply select the closest voltage you need & adjust from there.....it's not hard. Personally, I like the tapped units as there are less issues(dust/dirt) with the mechanics of a potentiometer. Don't let voltages be a main concern. A simple setup run on some scrap pieces of the material you will be using will give you a correct arc & you will hear the smooth burn(bacon frying sound) of wire to material. Popping, interrupted crackling, & burnback are indicators of incorrect settings of either voltage(taps) or heat(amps/w-f). Each unit will have a "sweet" spot for any thickness of material.....you just gotta find it. When you do, do as I do & make a notation in your notebook for future reference. Also, be aware of your gas coverage as indoors, 15cfh will be sufficient(CS) & a bit more(18-22cfh) if in a slight breeze(.023"= 3.5" of wire per amp>.030"= 2"   of wire per amp>.035"= 1.6" of wire per amp>.045"= 1"   of wire per ampIf you want 60amps of weld heat and have .030" wire on hand, the solution is; 60amps x 2"of wire per amp, or 120 inches per minute wire feed. You can work from burn-off charts to determine the best voltage if you have infinate control. With a tapped machine all you can change is stickout which will change the voltage by changing resistance in the circuit (this is limited but real). It also should be noted that the power supplies from all the big US makers assume that the user can "work" with stickouts from 1/4"-3/4" and use the machine... That's the way it is, if you want a tapped power supply that thinks 3/8" only is the pretty stickout... Build your own, they built this one.The big sale point of mig - "Old Timey" - was the power supply was "self regulating" but was easy and productive... Back then there was no chart inside a panel (nothing like set wire to 3 - set volts to 5 etc.)... The feeder was 1-10 the volts were 1-10 and burnoff charts were used starting with amps needed first... Amps needed were always set first by setting wire feed vs time, then the volts were set to make the weld play nice.If you use an O'scope to measure the voltage and amps while someone on the machine is semi-auto welding sweet with some motion on the torch, you quickly see the machine adjusting volts for constant power, it's just weird to watch the electric trace.MattLast edited by Matt_Maguire; 10-11-2011 at 02:26 AM.
Reply:I think that most of the confusion is due to the fact that stick welding (the oldest electric welding process) is done with constant-current machines, while the "newer" MIG process is constant voltage... and yet it's still amps that do the work!Even worse, the transformer type machines that most of us have used for decades do not make a true constant current OR constant voltage, but rather a useable approximation.Newer electronic welders can regulate current and voltage very precisely, but any decent-quality machine will work fine once it's "dialed in".Rather than over-thinking the technicalities, you can simply consult the manufacturer's spec sheet for the wire you're using, and use their recommendations as starting points. You can then tweak those settings as appropriate for your machine and for the job at hand.This is not made any easier by machines that use 1 thru 10 and A thru Z or whatever instead of WFS and Volts  but as shown by others it can be dealt with.JohnA few weldersA lot of hammersA whole lot of C-clamps