Need help w/ spray transfer on MM251

[Alex]

Andy or HAWK (on anyone else for that matter),
Some time ago I read a post on spray transfer using a mm251. Now I've lost the thread. I'm excited about the possibility since I've never owned a machine before that had enough snot to make it happen. I intend to use 90/10 for shielding and seem to recall HAWK said something around 27-28V. My questions are: Would .035 be more appropriate than .030? What wire speed would you start with? Do I need to jack up the gas flow? Am I correct in thinking that with .030 wire, I'm getting about 1 Amp per 2" wire speed?

Thanks a heap,
Alex

[GunLocators]

Alex here is a post off the Hobart forum that Dan started. http://www.hobartwelders.com/mboard/...ead.php?t=8516
Maybe it will help a bit.

[Danny]

Alex,

Crank the gas flow up to around 35 CFH. You're going to be holding a longer stick out then with short arc, plus the gas helps cool the gun. Also, i d recommend switching your nozzle on the gun to a nozzle that recesses the contact tip by an 1/8". The part # for the nozzle that i use is 169 724. For spray arcing with a MM 251 an .035 solid wire would be a better choice then an .030. The .035 solid wires spray arc range is roughly 165 - 300 amps, were as the .030 wires range is roughly 135 - 230 amps. The .030 is a good choice for spray arcing with a 210 amp unit like the MM 210, but limits you when your unit has the potential to spray @ 250+ amps. Machine setting are really going to depend on the material thickness and joint design. However as a starting point for 1/4" try somewhere around 450 on the wire speed and around 26 loads volts as a starting point. I don t have 90/10 yet ( still have a pretty full bottle of 98/2) to verify these settings. However, several months ago, i test drove the unit with 90/10 and if i remember right the above settings are pretty close to what i was running on 1/4" steel.

Also, no matter if it's short arc or spray you should be cleaning your basemetal to bright shiny metal. However, with spray this is even more important. Trying to spray arc over mill scale kills the arc quite a bit.

[Alex]

Dan,
I really appreciate the input. I'm with you regards .030 and .035 on 1/4". Stickout about 3/4", right? Have you tried spray on 1/8" yet? Also, I have a true 240 volt input, does that make a difference?

Thanks again,
Alex

[HAWK]

Dan,

Good advice. I really like the weld bead you have posted here and over on the Hobart forum. You mentioned really cleaning away all mill scale. Are the brown spots on this weld from mill scale or is that coming form you copper coated wire? Depending on the conditions I have seen both cause this. NO criticism here. It's a great bead. I am just curious about the spotting.

[Danny]

Dan,

Good advice. I really like the weld bead you have posted here and over on the Hobart forum. You mentioned really cleaning away all mill scale. Are the brown spots on this weld from mill scale or is that coming form you copper coated wire? Depending on the conditions I have seen both cause this. NO criticism here. It's a great bead. I am just curious about the spotting.

Hawk,

If you are referring to the silicon islands, I suppose it is a combination of the mill scale that i couldnt remove from the material, because of it coarse surface, plus the fact that I am using 98/2 oxy, which is going to require the silicon to scavenge more oxidizes from the weld puddle, then it would have to if i was using a 92/8 CO2 gas like you do. Now that i have a unit that can spray with a less oxidizing gas mix, once i empty this bottle of 98/2 , Im thinking about switching to 90/10 CO2.

[HAWK]

Dan,

Sometimes I get them too on 92Ar/8CO2 no matter how well I clean the material. The only time I am assured of getting a clean bright blown spray arc weld is when running National Standard bare wire with 92Ar/8CO2. Of course the material still needs to be reasonably clean.