Would this really work?

[oddbob]

This looks too good to be true...

https://www.youtube.com/watch?v=lrpQtijqe0g
I know little of such things ...but I thought MIG was voltage dependent and stick and TIG more about the current.

 

[mr migwire]

that looks like a handy little bit of kit.

 

[JayRS4]

Kinda like a Miller Suitcase, only more chinese

 

[rich r]

Yep the arc welder is just providing a constant current supply at whatever the OCV is (say 80 volts maybe). The converter's then just producing a constant voltage output to the Mig torch in exactly the same way as a normal Mig machine uses a 230V mains supply. It's probably an inverter type setup based around a boost converter.

As JayRS4 mentioned, these things have been around for a while from other manufacturers - quite a neat solution too.

 

[oddbob]

If it's worth a punt, I might get hold of one then (just found it on hebay). There are occasions when I wish I had a mig at my disposal, but I know, if I bought one, it would be collecting dust most of the time.

My skepticism is probably due to buying one of those Kel-ark gismos back in the 70's ...and finding it worked more like a kango than a welder!

 

[rich r]

Shifting voltages up and down and converting between ac and dc and back again can be done much more efficiently and effectively these days.

 

[Cobbler]

My skepticism is probably due to buying one of those Kel-ark gismos back in the 70's ...and finding it worked more like a kango than a welder!

I had one of those Kelarc things, in fact it's still on the shelf in the garage. It's a bit like the old joke "tried it once & didn't like it" perhaps I ought to put on the 'bay as a historic relic as dug up by Time Team.

EDIT, it didn't take 3 days to find out it didn't work either

 

[Bill Edwards]

If they designed it so you didn't have to carry the weight of the wire spool (by fitting the feed mechanism to the 'converter' and fitting a Eurotorch) it would have a good market.

Then they could compete with these: http://www.technicalarc.co.uk/index.php/tecarc-mig/wire-feed-units?page=shop.browse&category_id=26
Run off a generator welder too.
I think that unit be technical arc could be copied and sold for far less, if it wasn't for the price it would be popular.

 

[mr migwire]

If they designed it so you didn't have to carry the weight of the wire spool (by fitting the feed mechanism to the 'converter' and fitting a Eurotorch) it would have a good market.

Then they could compete with these: http://www.technicalarc.co.uk/index.php/tecarc-mig/wire-feed-units?page=shop.browse&category_id=26
Run off a generator welder too.
I think that unit be technical arc could be copied and sold for far less, if it wasn't for the price it would be popular.

the good thing about the spool gun is it tends not to birds nest the wire as it is the shortest distance from spool to gun which makes it ideal for ally welding.
I saw one of these on fleabay for around £70 which aint bad for what it is.

 

[mike 109444]

There has been an example of just a spool gun and fluxed? wire being used from car battery(s) to do repair to a 4x4 on an event day think there is even an example of one being used to repair a car in a car park on youtube somewhere.

 

[oddbob]

I've found an image of its innards...

...does anyone know what's going on in there?

 

[rich r]

Can't really see a lot other than a toroidal transformer and some capacitors I would guess there's some switching FETs on those heatsinks though.

 

[oddbob]

Toroidal transformer? ...that's good isn't it? ...Mararantz make a big deal of there being one in my amp!

 

[mike 109444]

I've found an image of its innards...

...does anyone know what's going on in there?

Lectric Magic now put that lid back on.......
.

 

[mike os]

Lectric Magic now put that lid back on.......
.

Yeah... don't let the magic smoke escape

 

[oddbob]

Well, I've got hold of one of these, thinking it might be worth a punt and if I didn't get on with it it could go straight on hebay.

It's fitted with very small dinse connectors, and although it comes with two adapters for 'proper' sized sockets, you actually need three ...unless you happen to have an earth lead with a 10-25mm plug on it kicking around ...so a bit disappointing that I couldn't use it straight out of the box.

Anyhow, all things considered, I'm reasonably impressed with it. I've had to run it using pure argon, 'cause that's what I've got, but it did manage to put down some tidy-ish (albeit very tall!) beads. It'll butt weld 1.5mm mild steel with ease and no likelihood of blowing through, but got a bit jittery when I put the amps down low enough to try some .9mm. I'm not sure if it's something inherent in it's design, but it really doesn't like the inverter being set below about 50/55amps. It also takes a lot of faffing with the wire speed to find the sweet spot, but that might be me to an extent as I haven't used a mig in a fair few years. The gun itself feels a bit on the flimsy side, so probably wouldn't be up to constant or heavy use, but the drive motor (16 watts) sounds and feels like it's up to the job.

I shall get some aluminium wire to try. If it runs that ok, it'll be worth having just for that, but it ain't no substitute for a proper mig ...so that's still on m'wish list!

 

[Jim Davey]

Looks to me like that control box doesn't do anything to change the fact that the power source has a drooping voltage characteristic and all the circuitry inside does is provide a variable voltage for the spool gun and a supply for a gas valve. The welding cables go in the back and straight out the front.
It's always been possible to MIG weld with the appropriate feeder connected to a stick set, but it's always been a pain to get a steady arc condition in dip transfer because the volts drop when the wire touches the job.
This is why you are struggling to set the wire feed speed correctly for the amps selected as stick welders do not make good mig power sources (unless of course they are designed from the start to be dual purpose, in which case they which case they will have a selectable CC or CV output mode)
By the way, the Tech Arc gun isnt a patch on the original and still in production JSF / Rowan Arc SP3 spool gun made now by its new owners MS Welding. It's been around for ever and the Globe motor alone is more than Tech Arcs whole gun but I've got ones out there near 40 years old still going strong.

 

[oddbob]

Looks to me like that control box doesn't do anything to change the fact that the power source has a drooping voltage characteristic and all the circuitry inside does is provide a variable voltage for the spool gun and a supply for a gas valve. The welding cables go in the back and straight out the front.
It's always been possible to MIG weld with the appropriate feeder connected to a stick set, but it's always been a pain to get a steady arc condition in dip transfer because the volts drop when the wire touches the job.
This is why you are struggling to set the wire feed speed correctly for the amps selected as stick welders do not make good mig power sources (unless of course they are designed from the start to be dual purpose, in which case they which case they will have a selectable CC or CV output mode)
By the way, the Tech Arc gun isnt a patch on the original and still in production JSF / Rowan Arc SP3 spool gun made now by its new owners MS Welding. It's been around for ever and the Globe motor alone is more than Tech Arcs whole gun but I've got ones out there near 40 years old still going strong.

Yep, that all seems to make perfect sense ...although I'm not sure what you're saying about the Techarc gun ...is the gun that comes with this a clone of that?

Anyhow, I think I'll have the cover of that 'converter' on Monday and see if I can see just what is going on in there

 

[Jim Davey]

Somebody mentioned the price of the Tech Arc gun and said they'd be more popular if they were cheaper.
I disagree, I think it's quality is already compromised by its price, the drive mechanism has some serious issues, the gun itself is flimsy and the motors lack of torque makes for inconsistent feed.
I like the fact it has a euro connector and will retrofit to virtually anything but having used the Miller and SP3 spool guns extensively (we've had SP3 guns on various Camarcs for 25+ years for the guys doing aluminium lorry body repairs and we're only just pensioning them off now because we have push pull guns and mini-feeds on the EWM pulse MIGs.) I'd say that in the long run the extra quality makes for greater VALUE which has nothing to do with price.
I just think that you can make any product cheap enough if you try, but getting it to work properly will be nigh on impossible. I've sold two or three TA 250 and 350 guns by the way and nobody was happy after they'd used them for a while, I discovered problems with them and was fed the usual line "nobody else has this problem", despite the fact I had the same fundamental issue with each gun I sold. I've had others in newer and older from other customers with the same problems too.
Certain things can be made on a budget and work really well, but I've not seen a spool gun yet that can be.

 

[Bill Edwards]

It was me who made the comment regarding the Tech Arc unit. Not having used one, but seeing them for sale while weighing up buying some welding gear. I didn't know they're poor quality, I assumed they'd do what they're sold to do.
The idea is great - any inverter, generator etc can be turned to a MIG unit that should be built to work properly, rather than the cheap spool gun that this thread is about which gives the impression that it does nothing to sort out the CC to CV problem that arises from using MMA sets.

I was thinking that if a unit that takes a Eurotorch could be made for a nice price that can concert a MMA inverter to a MIG with good results (as good as a dedicated MIG) then it ought to sell well.