What's the difference between short circuit and spray MIG welding?

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I'm taking my first welding class and they are starting us out doing short circuit and then we are going to move to spray, from what most of the advanced students say, short circuit is harder and never used anymore.  Any help or explanation would be appreciated.Thank you
Reply:Short circuit is likely the most widely used MIG process so I'm not so sure where those "advanced" students are getting their information.  There are actually three modes in the MIG process and all are determined by the voltage, wire size, WFS and shielding gas used.Short circuit transfer is where the filler wire actually makes contact with the molten puddle as the weld process takes place.  Short circuit typically takes place in the lower voltage ranges, is evidenced by the famous "frying bacon" sound with C-25 and CO2 being the common shielding gases for mild steelThen comes globular transfer that requires a higher voltage than the common short circuit and can be accomplished with the same shielding gases as with short circuit.  The telltale sound is alternating whooshing and popping and the filler wire drops off into the puddle in globs and only occasionally makes direct contact with the puddle resulting in the popping.And spray transfer requires the highest voltages and WFS and argon shielding gas with 15% or less CO2.  It is obviously the "hottest" of all transfer modes and lays down the most filler wire in a given time and exhibits a continuous whooshing sound.  In spray transfer the wire never makes contact with the puddle but rather "sprays" off the end in droplets as it exits the MIG gun tip.  Proper aluminum MIG utilizes the spray transfer mode and 100% argon as required by the material.This is just a brief explanation and more can be learned in the Miller website resource section.Last edited by duaneb55; 01-28-2014 at 03:40 PM.MM200 w/Spoolmatic 1Syncrowave 180SDBobcat 225G Plus - LP/NGMUTT Suitcase WirefeederWC-1S/Spoolmatic 1HF-251D-1PakMaster 100XL '68 Red Face Code #6633 projectStar Jet 21-110Save Second Base!
Reply:Nice explanation Duane.  I wasn't expecting it, but my MM252 went into the spray mode when I cranked it up to 29.5 volts and over 500 IPM. Definitely no doubt in the change of sound.Miller Bobcat 250Syncrowave  200Millermatic 252Spoolmatic 30ASpectrum 625 X-TremeMaxstar 150SVictor O/A torchesDewalt angle grindersWelded on/off for over 40 years.
Reply:Thank you, is the welding process much different between the two?
Reply:Check out my post #17 for three brief videos.http://weldingweb.com/vbb/showthread.php...ar#post3205261Dave J.Beware of false knowledge; it is more dangerous than ignorance. ~George Bernard Shaw~ Syncro 350Invertec v250-sThermal Arc 161 and 300MM210DialarcTried being normal once, didn't take....I think it was a Tuesday.
Reply:Great vid clips Dave.I would add that even though Miller (and others I'm sure) considers globular to be an undesirable "transition" transfer mode, one can approach achieving spray - let me call it upper end of globular - using C-25.It doesn't sound the same as in Miller's globular clip but more like spray with the "pop" every half second or so.  Basically on the threshold of spray but the gas is the limiting factor so it never quite gets there.This is what I mean:MM200 w/Spoolmatic 1Syncrowave 180SDBobcat 225G Plus - LP/NGMUTT Suitcase WirefeederWC-1S/Spoolmatic 1HF-251D-1PakMaster 100XL '68 Red Face Code #6633 projectStar Jet 21-110Save Second Base!
Reply:Hey Duane, I'm sure people use that form with good results - I just have not done so myself yet. I think you've made mention before of welding that way as well.Maybe someday I'll have tried everything - but then I'd probably be bored Dave J.Beware of false knowledge; it is more dangerous than ignorance. ~George Bernard Shaw~ Syncro 350Invertec v250-sThermal Arc 161 and 300MM210DialarcTried being normal once, didn't take....I think it was a Tuesday.
Reply:These loader bucket repair project welds were done that way with my MM200, .035 ER70S-6 wire, set on 6/High and C-25.  Don't recall the WFS.MM200 w/Spoolmatic 1Syncrowave 180SDBobcat 225G Plus - LP/NGMUTT Suitcase WirefeederWC-1S/Spoolmatic 1HF-251D-1PakMaster 100XL '68 Red Face Code #6633 projectStar Jet 21-110Save Second Base!
Reply:Nice   My MM210 should be able to get in the same voltage/amp range - now I better try it out Dave J.Beware of false knowledge; it is more dangerous than ignorance. ~George Bernard Shaw~ Syncro 350Invertec v250-sThermal Arc 161 and 300MM210DialarcTried being normal once, didn't take....I think it was a Tuesday.