how good Tweco Spray Master 450 Air Cooled MIG Gun?

Hi all
Shop I'm in is 100% dip-transfer and weaving. Everything matches, including torches. Common in UK. Torches rated "300A", but that's a
reluctant 300A and you spent a lot of time coaxing it to work at all. Frustratingly, can't "naturally" and cleanly get an 8mm (5/16th-inch) leg-length fillet, which is often specified for work done in this shop.
Unlikely to be able to change off Ar-20%CO2-2%O2 (get a messy globular transfer, unless on high thickness where very high voltage can drive smooth-ish spray transfer). At least for moment. Say go to 15%CO2 "compromise" or specially for me Ar-5%CO2 for spray only - maybe in future.
However, if could persuade shop to give me a bigger torch...
How good is the "Tweco Spray Master 450 Air Cooled MIG Gun"?
I kitted out another shop a few years ago with high-capacity air-cooled Binzels and changed them to Ar-15%CO2-2%O2 and they loved them and the resulting welding. Changes at the machine passed through in exact proportion to the welds and you could "tune" things, where under-capacity torches "muddied" everything and made cause-and-effect loose and uncontrollable and everything hard work just to get it done at all.
Basically, if I promise that getting one of these torches will do wonders, including "natural" 8mm (5/16th-inch) fillets (machine is rated to 450A), I want to know I'm promising the right thing...
Regards, Rich
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I can't really comment on that gun, but you can generally spray transfer at up to 10% CO2. I use 92/8 here in my shop.
What size wire do you run?
Randy
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Remove 333 to reply. Randy
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1.2mm solid wire (0.045inch?)
Thanks for comment.
You can help me out here. My employers are not believing what I am telling them. Maybe if I cited someone on-the-tools with an abundance of experience doing similar stuff to what we do they might start a process of re-thinking...
What sort of work do you do?
Where are you? There are different cultures in different parts of the world. We in UK FabCo's have the culture of "the dippy weavers" (they dip-transfer all the time and weave to make the fillet size). For them, they cling to an advertising tagline which caught-on from about two or more decades ago "5%CO2 for sheet metal 12%CO2 for general medium fab. 20%CO2 for thick" ("Argoshield Light", "Argoshield General" and "Argoshield Heavy", respectively. Purely a sales line.) You meet "experts" here in the UK who say "Oh no, you must use 20%CO2 2%O2 to get penetration in those thicknesses" (sic.). Looking at the big picture, that's about the world of the "dippy weavers". Just explaining so you can see how we ended up in this situation. Still with a lot of lack-of-fusion defects showing up on magpart...!!!
I'm running between 8m/min for the lightest - eg. 6mm web to 8mm end-plate (low but manageable with careful "push" torch-angle) 9.2m/min for lightest "clean" arc fillet on thinner structural steel 10.5m/min for general use on heavier sections 13.3m/min for 8mm fillets on >10mm smallest thickness T-fillets with a lot of heat-sink. I don't get to measure Amps and Volts as, although I have a tongues-tester / clamp-meter, there isn't acceptance of this stuff and even a few minutes of measuring would get me sacked, where everyone is completely busy "pushing along the cart with square wheels". I think that's somewhere around 300A.
All above I've quoted - that is while dealing with 20%CO2 gas - where with the right gas you might end-up at a different operating-point...
I suspect the gas pushes you to a higher voltage than you'd have with a gas like you mention. The fusion is "monster" - you can see the arc excavating the fillet-corner. That might be giving me big shrinkage pipes at the ends - mega-melts the corner where you finish the run. Tried running from each end and "splicing" in the middle, but they responded with vigorous disfavour to seeing the weld-stop in the middle of the weld-run. Engineeringly - there's usually not much going on stress-wise in the middle of the length of a fillet - so appears an idea solution - plus can get at it with an angle-grinder if you "muff" pumping the trigger to crater-fill - given bit inexact when on 4-way-latch.
Overall though, a messed-up situation.
Would be delighted if you'd let some light into the situation describing what you do in the context of where you come from.
I know even 15%CO2 has a magical effect in enabling the arc condition to become "clean" with a well-defined small (about 3mm-high?) spray-cone and zero spatter. Helped out another UK fabco a while back, in order to know this... There is a bottle of 12%CO2 in the cage "for the site guys" - but again, I'd get sacked if I touched it.
Interested in this 92/8. Sounds ideal. No oxygen in it? Bit of O2 is reckoned to increase weld fluidity and *help* the transition to spray-transfer(???).
My welds are completely "clean" on magpart - not even spurious possibles to discount - which is a new experience for my employer. So in with a chance, if can put to them some real-world experience.
We make mainly quarrying equipment, by the way. Gets rough use, but doesn't have to please a high-street consumer's nor a nuclear-inspector's eye. Do need to be ready to put a UK inspector in their place who has never before seen fusion, wetted-in fillet edges and therefore a divot in the weld at the end. Yes, really! - someone who has only ever seen "dippy weave" welds...!
Thanks in advance, Rich Smith
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I can't be much help, I very rarly do any filets that big. 92/8 is Argon 98% CO2 8% no oxygen at all. 90/10 works good for spray transfer too.
You guys, in my opinion, should be using spray, speed is almost double that of short circuit transfer. You need to get a weld supplier in there to demonstrate that for the boss. It should impress the hell out him.

https://www.youtube.com/watch?v=IHkbh0oKv_g

In this video Miller says you can even use 15% co2 to spray transfer, I was always told keep it to 10% max. O2 only for use with stainless steels.
Faster speed, higher deposition rates, nicer bead appearance, less spatter, what's not to like. It does take more power and your power source has to be up to te job.
I'm wondering if 0.045" wire is big enough for a 5/16 fillet in one pass. I was using .045 for 1/4" fillets.
Maybe even if you have to do it on your own time, lunch maybe?, call Miller's or Lincoln's help support line and talk to them. They can give you real answers.
What brand of power source are you using, start by calling them.
Randy
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Even Ar-15%CO2-2%O2 is so nice compared to Ar-20%CO2-2%O2 - I think it is true that 15%CO2 is the upper limit for good spray transfer. Suddenly getting the spray-cone as lift out of dip at about 220A and suitable voltage.
1.2mm wire is fine. Problems come with using 1mm (0.040") wire especially in an air-cooled torch - can spray fine with 1.2mm wire where same torch "craps-out" with 1.0mm wire. You need 1.4X the wire-feed-speed - as you'd expect (dia ratio 1.2:1 -> area-ratio 1.44:1 -> wfs 1:1.44 - then there is 1/1.2 (83%) of the contact area - plus probably more Ohmic heating in the wire - again 1.44:1 - all stacking up towards making the torch crap-out on the smaller wire.
1.2mm wire is OK for most dip-transfer for low thickness in anything but a sheet-metal shop. Any larger would not be operable for small thinner jobs (?).
In the UK, the sales rep.'s will pedal the "Argoshield Light/Medium/Heavy" lines as if it were written on tablets of stone and handed down to an Earthly emissary from God.
Machines including my machine is "Migatronic". It's a big very heavy copper-and-iron transformer rated to 455A, and I have no suspicions regarding its ability to do the job. BTW - some of the **** I've heard from "experts" is that you can't spray without a "modern" computer-controlled welding machine. Spray transfer volts and amps are as flat as a billiard table even when sampled at 20thousand times a second - I know 'cos I've done it... Doesn't need anything fancy. Copper-and-iron MIG machines with voltage-tap setting and wire-feed-speed "pot" (the knob you turn) works totally fine with spray.
I find especially in cities that you had to finely adjust the WFS pot. every few minutes to keep the welding condition constant. Stopped others copying me, when I was the only one who could spray and the owner of the fabco had instructed the foreman not to put me on welding because I couldn't weld (sic.) :-)))))))))))
Faster speed - well yes - as Amps is proportional to wire-feed-speed, it means I must be running twice the deposition-rate seeing as I have twice the Amps.
You can tell me - what sort of things to you make? If I have to quote an example, knowing that is likely to impress...
Regards, Rich Smith
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wrote:

I am mostly a machine shop. I do a little welding now and then. I used to do more welding, but I am trying to keep to mostly machining these days.
I am using an ESAB DIP-PAK 250, old copper/iron transformer machine and it can spray transfer just fine. ( obsolete machine, getting difficult to find tips and nozzles for it)
These Usenet groups are not what they used to be. I would look for a public forum on a welding supplier site. You should be able to get some real advice from someone in the heavy fab industry.
https://forum.millerwelds.com/
Randy Remove 333 to reply. Randy
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Thanks for chatting with me about this. You gave me some good things about how it works in the world you experience. The one about lower CO2 for higher thickness is a completely different outlook - that as you always spray, the CO2-proportion goes down. Experienced welding engineers here for the likes of oil&gas cite that they have "spray-only" higher power MIG / GMAW setups which use 5%CO2. Which is what you cite. I need to have another conversation with my employer - the time has come. Regards, Rich Smith
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