Voltage vs Amperage?

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I have a lincoln SP250 and many of you may remember the trouble I was having with the welder. Well I figured out the problem when I got the welder the polarity was reversed! Since you can choose flux core or solid wire in the digital panel I figured the machine did it on its own so that never occured to me!! Needless to say I feel spoiled to finally have a "nice" welder finally but I seem to have trouble setting the welder for <3/16. It has presets up to that that seem to go incrementally so if I am welding 1/4 I try and move the voltage and ipm up at the same rate. It welds ok but it doesnt sound right and produces splattery kind of "lumpy" welds.  Does voltage have the same effect that amperage does? I have .030 wire in it (??) maybe .035 and 75/25 gas. Any suggestions? I can get up to around 27 volts and 500 ipmHTP Invertig 201Lincoln Idealarc SP250Miller 180 AC StickBy farmall:They should have held the seagull closer to the work, squeezing evenly for best deposition.
Reply:The voltage is your heat control.   If I remember right this machie is multi-process?  You have the welder in Constant Voltage wire mode  and the polarity set with the torch positive, work negative (reverse polarity) right?   Your controls should be voltage, wire feed speed and inductance.   For .035" ER70S-x wire with 75/25 Ar/CO2 gas and 1/4" plate in flat or horizontal position with short circuit transfer, the chart on my 350P says the setting is 19.5 volts, 330 inches per minute, inductance set at 20 to 40.   I don't know if your inductance control would have the same values as mine.   The higher the inductance number on mine, the softer the arc and more fluid the puddle.  I like it around 30.Lumpy, non penetrating, poor wetting welds indicates to me you don't have enough voltage (too cold) or you're moving the torch way too fast.  Set the voltage first then fine tune it with the wire speed.  The wire speed is your amperage control.  Play with the voltage between 19 to 20 and the wire speed between 300 to 350 to get it welding how you like it.   Set the gas flow around 25 cfh.If you're doing a butt joint, prepare your joint with a gap of at least 1/8" if you're not beveling any edges.   It is best to bevel both plates so you have a 45* angle between them so you get down into the root.Last edited by DesertRider33; 01-26-2009 at 08:57 AM.MM350P/Python/Q300MM175/Q300DialarcHFHTP MIG200PowCon300SMHypertherm380ThermalArc185Purox oaF350CrewCab4x4LoadNGo utilitybedBobcat250XMT304/Optima/SpoolmaticSuitcase12RC/Q300Suitcase8RC/Q400Passport/Q300Smith op
Reply:I dont know what this inductance is...HTP Invertig 201Lincoln Idealarc SP250Miller 180 AC StickBy farmall:They should have held the seagull closer to the work, squeezing evenly for best deposition.
Reply:INDUCTANCE: Power sources do not respond instantly to load changes. The current takes a finite time to attain a new level. Inductance in the circuit is responsible for this time lag. The maximum amount of current attainable during a short is determined by the slope of the power source. Inductance controls the rate of rise of short circuit current. The rate can be slowed so that the short may clear with minimum spatter. The inductance also stores energy. It supplies this energy to the arc after the short has cleared and causes a longer arc. In ”short arc” welding, an increase in inductance increases the ”arc on” time. This, in turn, makes the puddle more fluid, resulting in a flatter, smoother weld bead. The opposite is true when the inductance is decreased. Info from ESAB and the link below.http://www.esabna.com/EUWeb/MIG_handbook/592mig3_6.htmWelding is my hobby, I just happen to get paid for it!
Reply:He made it sound like inductance was adjustable...?HTP Invertig 201Lincoln Idealarc SP250Miller 180 AC StickBy farmall:They should have held the seagull closer to the work, squeezing evenly for best deposition.
Reply:Originally Posted by fordmanHe made it sound like inductance was adjustable...?
Reply:Voltage is NOT 'heat'.The wire feed speed is the amperage, which is the 'heat'.But to get the arc at a certain (range of) wire feed speeds (amperage settings) takes a certain voltage (or range of voltages).Different wires have different 'ranges' of acceptable voltages for any amperage/wire-speed, and sometimes the difference between the correct voltage and too-high or too-low is only 1/2 volt.Also the correct voltage depends on the gas or gas mix being used (plain CO2 typically is 1-2 volts higher than a C-8/C25 gas mix for the same wire speed aka amperage).  And if you were doing aluminum with argon and then argon-helium, the helium mixes use more voltage than plain argon.General troubleshooting:Low arc voltage : wire stubs into workHigh arc voltage : arc is unstable (spatter)Set the voltage midway between high/low voltageWire speed (amperage) controls penetration.Voltage controls height and width of weld bead.Although higher wire feed speeds (amperages) DO need higher voltages, you usually don't have to adjust the voltage for 'minor' WFS/amperage or work thickness adjustments.And there is an appreciable difference between 0.030 and 0.035 solid wire.For short-circuit transfer (as opposed to globular or spray transfer), 0.030 wire has a rough usable amperage range of 40-145 amps and gives you 2 ipm/amp while 0.035 wire has a rough usable range of 50-180 amps and gives 1.6 ipm/amp.  So at an (arbitrary) example WFS of 250 ipm, the 0.030 wire would be approximately 125 amps and the 0.035 wire would be at approximately 150 amps.  Driving the wires faster than those rough usable amp/WFS ranges and you are usually going past short-circuit transfer and into globular or spray transfer, where those nice linear ipm/amp relationships no longer apply and the relationship is exponential instead.  BTW, for 0.023/0.025 wire, the rough usable short-circuit range is 30-90 amps and the linear WFS/amperage relationship is 3.5 ipm/amp.  At the arbitrary example WFS of 250 ipm, that would give about 71 amps for the 0.023/0.025 wire.Spattery lumpy welds?  Leave the WFS alone and turn DOWN the voltage slightly (or to the next lower increment if the machine is a tapped voltage unit and not a continuous voltage unit).  Try the weld again at the lower voltage.  If the wire stubs into the work at the lower voltage, then turn down the WFS/amperage slightly and try again.Lumpy 'wormy' weld bead?  Probably moving the torch/gun too fast.Lumpy wormy and spattery weld bead?  Probably have the voltage too high AND you are moving the torch/gun too fast.Other than that, pretty much what DesertRider33 said about general parameters and such.  Read through the info on the ESAB site on GMAW from the above hot-link.  You can also read info on Lincoln's website about GMAW (search through the info/documents there, Lincoln "GMAW Welding Guide" document c4200 http://www.lincolnelectric.com/products/litrequest/).Generally, change ONE thing at a time and recheck.Hmm, the SP250 manual  (IM397) from Lincoln shows that the machine is a 'fancy' one with touch panel keys/buttons and 'auto' settings.  It looks like you really have to make sure you tell the machine the right input information (wire diameter and gas type) in order for it to adjust the arc parameters properly, especially in AUTO mode.  Also, the manual says that the gun for the SP250 has a control switch on it as well, and you have to tell the machine what the gun switch is controlling.  The best laid schemes ... Gang oft agley ...
Reply:thanks alot for your help guys, I will play with it when I have a chance and show you guys.. So could you weld at a high WFS but low voltage or would that not work to well? Say 400 ipm and 18 volt? Well Ill give it a shot and well see! I need to measure the wire and see what I have in there, ive forgotten hahaHTP Invertig 201Lincoln Idealarc SP250Miller 180 AC StickBy farmall:They should have held the seagull closer to the work, squeezing evenly for best deposition.