So ever since I learned about dual shield flux core, I had this nagging suspicion. The larger flowrates "required" by some literature might be due (in part) due to the very long CTWD necessitated by the DSFC process. With 0.045" E71T-1C/1M, the process needs about ¾ - 1" of "stickout" from the tip, so I could definitely understand needing upwards of 40+ CFH to make sure the shielding gas covers the spread considering that most MIG guns either have the contact tip flush or just slightly recessed; so the nozzle orifice itself is anywhere from 1" to perhaps 13/16" away if it happens to have a recessed tip. So I thought, what if the nozzle was simply longer, to the point where the nozzle orifice was approximately 3/8" away from the weld joint, similar to what on would use with short-circuit MIG with typical wire diameters? Would it still "work"? I'm only a hobbyist, so "work" has a looser definition for me than a professional, so what they heck, try it out.
So I got bought some extra nozzles, chucked them up in the lathe sliced them up to make a predetermined nozzle length (in order to "bury" the contact tip with a huge recess) and cobbled together a longer frankenstein nozzle to try out.
Here you can see my standard nozzle (the nickel-plated copper one), and the new mega nozzle. 82.2mm vs 92.5mm. With this setup, I only need 3/8" - 7/16" stand-off distance from the nozzle to the work. First try with only 27CFM of C25 worked great. Close enough to really cut down the shielding gas use, but far enough that it doesn't obstruct the view.
I basically took a cylindrical nozzle, and took off a length, and attached the top of standard conical nozzle so as to have them meet on the flat part and not the taper, and just spot welded it all the way around. Didn't use any filler or anything, just autogenous tacks all the way around. It just needed to not fall off.
Other than the nozzle getting hotter because it is closer to the arc, worked out great for me. I guess if I feel really ambitious I could add water-cooling to the nozzle to wick-out the heat, but that will be a project for another day.
mig and flux core tips and techniques, equipment, filler metal
Believe it or not, that idea crossed my mind as well. Honestly it would depend on the gun itself, or rather the configuration of the diffuser/nozzle that would ultimately determine if you could shove a custom made gas mesh screen to straighten out the flow. You can only drop the flow so much even with a mesh screen, due to the size [of the opening] of the typical nozzle used for dual shield. I suspect that even with a mesh screen stuck up in there, you won't be able to go much lower than about 23 CFH, since the standard conical nozzle is roughly 5/8" orifice at the nozzle's end, and a conical nozzle is 3/4"-7/8" opening. But then again, there are also smaller MIG guns that use smaller nozzles since they can typically use 0.035" dual shield wire, so those would use even less. My HTP ProPulse 200A MIGs have Euro style MB24KD guns, so those are more suited to 0.035" dual shield. The weld bead I ran was with my MB36KD mig gun that came on my Pro Pulse 300, but I installed it on my Pro Pulse 220MTS since the wire was Lincoln 71M in 0.045" size running at approximately 220A, gun did get a little "toastier" than it normally would, so that is the only downside. Obviously you wouldn't run this on a production type run with high duty cycles.
depending on the diffuser design, that may or may not work. Some diffusers are separate pieces (like mine) and some are built into the tip holder. One has to carefully evaluate these things since the sizes are purpose-built.tweake wrote:i've toyed with the idea with aluminium mig welding.
even just making a spacer to go behind the nozzle so its pushed forward a bit.
I just made another one for one of my smaller MIGs, that uses an MB24KD mig gun. This is for running 035 dual shield.
In this one, I integrated from the beginning, a slight 2.5° downward droop to the conical tip I welded on. This takes into account the downward slope the wire takes when using the mfg recommended stickout.
Using 0.035 E71T-1C/1M. Ran beautifully. Only needs 5/16" to 3/8" from nozzle-to-work to achieve the mgf required ~7/8" electrical stickout. I only used ~19 CFH for this.
No porosity or any other such purported issues. Just a nice clean weld without wasting a crap ton of shielding gas.
In this one, I integrated from the beginning, a slight 2.5° downward droop to the conical tip I welded on. This takes into account the downward slope the wire takes when using the mfg recommended stickout.
Using 0.035 E71T-1C/1M. Ran beautifully. Only needs 5/16" to 3/8" from nozzle-to-work to achieve the mgf required ~7/8" electrical stickout. I only used ~19 CFH for this.
No porosity or any other such purported issues. Just a nice clean weld without wasting a crap ton of shielding gas.
I have no problem with you thinking that, lol. All I know, is it validated my hypothesis, and it works; even if it wasn't a full-blow scientific experiment. It was solely hobbyist level tinkering, as I call it.
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