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Spray Transfer!

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  • Spray Transfer!

    I did my first spray transfer fusions this evening before dinner.

    MM 251 w/ M-25 gun; tip barely proud of nozzle for short-circuit transfer.
    Argon tank
    CO2 tank
    Western Enterprises Dual gas mixing Y valves
    Victor CO2 flow regulator
    Victor Argon flow regulator
    Gas flow tester for use at gun nozzle
    Miller Digital Infinity helmet

    Base material: 1/8" carbon steel.
    Filler: LE SuperArc L-56 (ER70S-6), 0.035"

    First, I thought I had some longer nozzles, but nope, didn't. So used a nozzle with a widened mouth, the tip is just proud of the nozzle end.

    Secondly, I increased my helmets darkening to the max and wore some uv-blocking shop glasses which normally block my vision while short circuit transfer welding. Glad I did. Figured that the much higher electromotive force would be a blinder.

    Adjusted the argon regulator to 30 cfh and CO2 to roughly 4 cfh, for a total of 34 cfh, all measurements taken at the gun nozzle. If these gasses both weighed the same, it would be roughly 86/14 mix. Very roughly. Sometimes the Ar flow was measured at 32 cfh with a total of 34 cfh (roughly 94/6 by volume, not weight). So obviously using this kind of mixing is not spot-on by any means.

    First spray weld was a lap joint with two 1/8" pieces at 28v, 350 ipm, run-in at 100%. Wow. Reasonably nice looking weld even with really sloppy technique as I saw a lot of undercut so I was trying to increase my travel speeds. Manipulation was forward then back half way, linearly, but quite jerky. Toes looked smooth, weld was relatively flat, really smooth surface even though I was manipulating the gun forward and aft.

    So I played around with the wire speed and voltage. Found the Spray transfer minimum threshold at 27.6 v. Below that, globular. Very distinctive by the droplets forming just above the puddle. After that voltage, a spray cone was clearly visible. 28v seemed to be the sweet spot on my machine. The cone was very visible after initiation, with it stabilizing at about 0.25" above the puddle. Found that the best tip to base distance was just over an inch. Can't really call it stickout, because I trimmed the wire to the nozzle before each start, and noticed that as soon as an arc was established (before the wire had a chance to extend), a cone would form just below the tip. Within about 0.5 seconds or less, the cone apex would then collapse down to 0.25" above the puddle. Really cool to see that phenomena.

    So after quite a few passes with lap joints and butts, found that 28.5v / 440 imp was the sweet spot for the 1/8" material I was using.
    The wire speeds stated are only machine displayed outputs, not actual wire feed speeds. Didn't have a chance to measure actual as my beautiful wife was calling for dinner. Typically, my machine's actual feed rates are roughly 94% of displayed rates, so a guesstimate would be 413 ipm.

    Also, i normally (short circuit) use thinner mig gloves with a aluminized kevlar heat shield on my support hand, which is positioned near the nozzle for good manipulation control. You can imagine where I'm going, right? Trying to keep myself aware of 'stickout' distance, I used my normal prop position. Within just two lines (12 inches each), that shield that had done so well for so long was completely roasted. I could put a dime through the hole that the wicked heat drilled through the shield. No joke. That spray is hot. The remainder of the beads were done with my prop hand covering my trigger hand. Shield doing a respectable job at that distance. I'm gonna have to get me a couple of new shields. I'll be using my THICK glove on my prop hand.

    I kept the travel speeds high while keeping the welds looking respectable. Experimented with some manipulation. Very nice looking welds. The thin steel did not warp. I don't know why.

    Things to do:
    Purchase longer nozzles.
    Add less CO2 possibly.
    Measure wire feed rate at these speeds.
    Try my polarized sun glasses beneath the helmet for less glare. May or may not help.
    More heat shields!

    Anyway, this exercise was to test the mid-range capabilities of my machine (purchased this well used but in good condition), and to prep myself for some aluminum spraying.


    Edit: Initiated arc with a 0 deg (from vertical) angle, then proceeded with ~10 deg push. Worked well.

    Initial sound was like a small jet engine, but as the cone diminished in size within less than 0.5 seconds, the 'jet engine' sound became quieter, and very smooth sounding.
    Absolutely no splatter! But there was a tan-colored dusting over everything that easily brushed off.
    Last edited by DougM; 03-28-2018, 06:43 AM. Reason: spray, mig, gmaw

  • #2
    Pretty detailed explanation, Doug. I love spray transfer. I have an old MM250, it's a bit of a beast and about as harsh as they come, but it loves to spray as well. I don't use any manipulation when weld with spray transfer. I'm guessing the only reason you're spraying on
    .125 material is that's what you have. You should consider getting something heavier for more realistic practice.


    • #3
      Hey Ryan.
      I was messing with .125 stuff in SC mode, and wanted to see if I could spray it as a whim. I've plenty of heavier scrap laying about, but thought spraying the thin material without much warpage could be good practice for aluminum spraying, practicing high travel speeds.


      • #4
        Also tried zero manipulation, and that worked best on butt and lap joints. Likely heats the base metal less than manipulation does, right? I was primarily doing the linear manipulations as beads to see how it all behaved.


        • #5
          Excellent write up and observations! Thank you for posting. I've not done any spray in a long time. Used to do it with my old PowCon 300SM, and I did get my HH210 to spray with .023 and C3 gas, but only as an experiment, not to really use it for anything.


          • #6
            Thanks Mac, however I discovered this evening that I was mistaken about the base material thickness. It was not 0.125", but 0.135" (10 gauge) mild carbon steel.
            I tried the same settings (28.5v / 440 ipm indicated, 432.5 measured) on 11 gauge 2" square tube, and received completely different results. It was like a fire hose through wet toilet paper with a travel speed similar to spraying on the 10 gauge material. Speeding up the travel speed stopped the plasma cutting, but the weld bead was too stringy, thin, and tall with abrupt toes that didn't look like they fused well.
            I couldn't find any 0.25" material, and I could not find an adequate V / feed rate solution for the 11g, even though I tried to vary current with longer tip-to-work distances (I=V/R).

            I did however try spraying beads onto a 1" (0.992") piece of mild steel. (Now we're talkin'!)
            > 29.1v / 471 ipm indicated (482.5 ipm measured) with 0.035" ER70S-6 wire did a fine job, however after about 8" of bead, I got some stuttering. Would this be from contaminated wire? Wire appeared good though, opened one month ago, and resealed when not in use. Perhaps the nozzle wasn't sealed well, or turbulent gas flow. Don't know. After restart, the spray would sound outstanding for another eight or so inches. Then 'pop' shshshshshshshsh.."pop" shshshshshshsh."pop..pop" shshshshsh.... The beads had externally visible voids where the pops took place. The base surface was sanded bright.

            Of course, at 482 ipm, the 0.035" wire is past the linear part of it's current / feed rate curve and firmly within the exponential part of the curve. I don't know if that has anything to do with the popping.
            The spray cone was most definitely different than on the 10 g steel. Much taller as well as wider at the puddle, just as you'd expect from a larger cone. More voltage, bigger cone.

            Ha. Just thought of something. Could the larger cone create more gas turbulence, possibly introducing the atmosphere into the plasma column? I was running ~38 cfh ~95/5 Ar/CO2, so perhaps I shoulda increased the gas flow up to 45 cfh. Both CO2 and Ar tanks are nearly new and near-fully pressurized.
            Magnetic blow?!

            Also noticed that measured feed rates varied for one feed setting. Wonder if actual feed rate varies slightly with a change in voltage, or perhaps I merely need to change the gun liner?

            Edit: Tried using my dark-gray polarized oakleys under my helmet. What a difference. The arc is much less intense, but the surrounding work is a bit easier to see. But I think I got a little arc-burn on my face. The front of the helmet was quite hot after messing with the 1" material. The digital infinity has a darkening intensity range of 8 - 13, and I put it down to 11 with the sunglasses on. I've some yeller colored polarized lenses i can put in the oakleys, so perhaps I can keep the helmet tinting intensity up to the 13 level.
            Last edited by DougM; 03-28-2018, 07:49 PM.


            • #7
              To answer your question about weaving, yes, it puts more heat into your metal simply because it slows your travel speed down a skosh. That's why a lot of times stringers are required over weaving.

              My MM250 welds aluminum like a bad dog using 3/64th 5356. I made a short whip just for welding aluminum. Granted, I don't do it much because it's really only good for heavy aluminum and I prefer to tig it anyway.

              I also wear the sunglasses under my hood when I spray. ****, I even wear them when I'm doing a lot of continuous welds regardless of the process. But even with the extra eye shields on, I still get the big blue dot in my vision after doing a lot of spraying.

              Sounds like you're having some fun over there throwing some hot wire down though.


              • #8
                Yeah Ryan! Fun fun fun. Any idea on that popping problem?
                Forgot a detail: Initiating the arc on the 1" material was different than on the 10 gauge stuff. As stated before, with the 10g spray, the wire seemed to immediately atomize and form a cone as soon as I pressed the go!-switch, and the wire never contacted the base. On the 1" material, this did not happen. I could feel the wire impacting the base, then the wire became atomized, but the cone never really shrank as it did on the 10g example. It didn't give me that absolutely perfect start like the 10g did, but the beginning of the bead looked fine. After the arc was initiated, everything seemed good, except for that confounded popping after 8 inches or so. I did adopt a different work-to-tip distance, down to roughly 0.5" to 0.75" from +1", and perhaps that was the reason. I'll have to try again.


                • #9
                  Was your 10ga. lap joint laying on a bench so it was backed up by the bench while the tubing joint would have no backing?


                  • #10
                    And check the ground. When I have goofy starts, my first place to look is the ground. Needs to be on bright shiny metal. But it sounds like you might have already solved it with the stick out issue. I would think 1/2" is too close for spray arc. Might be getting some gas turbulence when you're that close. Travel speed inconsistency maybe?


                    • #11
                      Hey guys,
                      Yup, I always ensure the ground is attached to bright metal, and always attached to the base metal, with the heavy, bronze clamp freshly brightened as well.
                      I have been getting very consistent width and height beads with no manipulation, very nice toes that flow out and almost tangent to the base surface.
                      The shorter stickout could be a likely culprit. I was experimenting with controlling the amperage with varying stickout. However, it still happened with a longer stickout of +1". I had been using a tip that had burned back during some bad globular episodes,so I deburred and drilled it and it looked fine. Could be with the short stickout it got too hot and pinched the wire momentarily , and then cooled well enough after I ceased for a moment, then repeated as it heated up again. I believe it was originally a 0.045" tip, and I made sure the orifice with the 0.035 wire felt large enough and smooth-working, but I'll try a new 0.045" tip.

                      Meltedmetal - Yes, the 10ga work was laying on the steel welding bench, but I would say it was NOT laying perfectly flat since it was already somewhat distorted from it's use in another life. And like you stated, the tube had no backing behind the welding surface. Hmmm. Would this really be an issue? I figured it was merely the amount of heat that the thinner metal could not absorb --- oh, gotchya. I see where you're leaning to (the bench absorbs much of the excess heat). Some sort of internal heat sink (square bar?) may work with the tube, eh?

                      Amazing how clean proper spray transfer can be. No crud on the tip or nozzle, no splatter, nothin'. Just some awesome looking beads, intense heat and lots'a UV radiation (prob'ly additional rads worse than that). My long-sleeved, dark blue, heavy carhart shirt was lookin' like it was well bleached after my experimenting yesterday.

                      About the grounding again.... would it be beneficial to have multiple ground clamps, each connected to it's own lead, each lead connected a few feet from the machine? Or heck, all the way to the machine's terminal? Due to operating in DC(EP), I wonder if that would reduce magnetic interference? Especially in corners.

                      Thanks guys!


                      • #12
                        If you have some more 10 ga. tack up another lap joint and put it in a vice or lay it so it is only supported at its ends and retest. That should tell you if the bench was sucking heat away from the weld.


                        • #13
                          I don't think you'll gain anything with multiple ground wires. My machine pops once in a while when spraying too, there's just so many variables that it's hard to get down to one without being there. As long as it's just a pop once in a while and it's not affecting the weld, it'll probably be fine. When abouts on this planet are you?


                          • #14
                            Ryan, I'm near Mt Airy, NC.
                            I figured out the popping. At least I believe i did by attacking on multiple fronts all at once.
                            First, replaced the tip (0.045" tip for 0.035" wire). Yeah, it was probably the culprit. The one I was using while the popping was happening was burred a bit, and i could feel the inconsistencies with a torch cleaner. Frack it, just replace the thing.
                            Also bumped up the gas to 42 cfh.
                            Made sure to use at least 1" stickout.

                            This was on 1" (0.992") mild steel, and it sounded sweet the whole time, like a small, well-tuned jet engine.
                            I was happy that all was good on the steel side of things, so didn't waste any more time and set the machine up for ...

                            ALUMINUM SPRAY!

                            MM 251 w/Spoolmatic 30A

                            Base material: 0.25" 6061-T6, Well degreased and abraded
                            Filler: 0.035" junk 4043
                            0.035" Maxal 4943

                            Started off with the 4043 of unknown origin and age. 26v / 500 ipm indicated. Not too bad. Kinda chunky looking though, even using a 10-15 deg push angle. Think it was due to the age of the wire and it looked as though it had been rewound on the 1 lb spool. Not much wire. Made a few beads, then attacked one side of a lap joint (12").
                            Looked as though their was some small voids. Luckly, the spool ran out and welded the tip before I wasted any more time messing with the controls.

                            Slapped some new 4943 in, adjust the gun, and started with the same settings. Nice.
                            So found that with the base material at room temp, a good starting point is 27v / 600 ipm indicated. Then as the base warms up, go down to 26v / 550 ipm.
                            This spray sounded like a much larger jet engine compared to the steel spray. Also found that the far ends of the aluminum stock became hotter than near the welding point, especially under the ground attachment point. I used an infrared thermometer, but then compared the reading to the bench and was dismayed that the bench read hotter than the aluminum. Duh. Infrared thermometers don't accurately read temps off of aluminum or anything else with a certain amount of reflection. So, who knows if my relative temperature assumptions were correct.
                            That brings me to the question of: how do you guys measure your aluminum base temperatures? Bi-metal thermocouples?

                            Also, got that nice lookin' soot. Played around with different push angles, and none really made a noticeable difference. Bumped the Ar up to 48 cfh and nothing changed. Perhaps turbulence raised it's ugly head, or I need to place a gas diffuser inside the nozzle. Something like scotchbrite.

                            So, I cut the test coupon down the middle, across the lap joint, and all beads and joints looked really good. Zero inclusions. I had gone over the crappy lap I had done with the old 4043 with the new 4943, and that weld looked good too.

                            -doug out.

                            It was good that I got a little experience with steel spray transfer before I explored Aluminum spray transfer. Certainly not the same, but still somewhat similar. Travel speeds are much faster than short circuit transfer, and experimenting with steel allowed me to experience and correct for some issues such as globular transition points, extreme heat, varying the current with stickout distances, etc.
                            I think, however, that the 0.035" aluminum wire is a bit too small, and that 3/64" (0.047") would be better for the 0.25" aluminum plate for T-joints and perhaps lap joints. For a project that I need to complete, I am considering using a one-sided beveled butt joint, since it will be impossible to reach from the opposite side. Perhaps 0.035" wire would be good for the first pass. Err... or not.
                            Last edited by DougM; 03-30-2018, 06:56 AM.


                            • #15
                              I found that I'll have to purchase an IR thermometer that has adjustable emissivity to accurately take the temperature of aluminum and bright steel. Something like a Fluke 62+.
                              What do you guys use?
                              Last edited by DougM; 03-30-2018, 10:27 AM.