Could I run MMA (Stick) from my Migmate?

[aesmith]

Hi,

Since I've been in about the innards of my Migmate 150DP it got me wondering whether I could rig it for stick welding as an additional option. I was thinking along the lines of wiring a hefty DPDT switch, one position would bypass the switch on the torch with one pole, and isolate the wire feed motor with the other pole.

Before I investigate how to get at the appropriate connections, is there anything fundamentally wrong with this idea, in that the output would be unsuitable for MMA? Also, which polarity should I use, torch +ve or torch -ve?

Thanks, Tony S

 

[Spark plug]

It wouldn't work because mig uses a constant voltage output whilst MMA needs a constant amperage output.

 

[BrokenBiker]

wont work. Only works on inverter migs because they have a separate circuit board for stick welding

 

[aesmith]

Thanks, glad I asked before spending time on the idea.

 

[rtbcomp]

Has anyone actually tried it?

 

[PTvor]

Has anyone actually tried it?

In view of the cost of the bits and pieces to do this and the time, weighed against a second hand buzz box (£20-£30) designed for MMA, I wouldn't be inclined to experiment along these lines. Codging it like this would also make the MIG welder harder to sell.

Don't forget the OCV needed for MMA and the fact that with an arc welding transformer, the OCV doesn't change that much when the current setting is changed.

 

[rtbcomp]

I realise that, but it would interesting to see what would happen. Personally I suspect the rectifier might suffer if the rod sticks.

I'm guessing a buzz-box is operated at saturation so short-circuit current would be limited.

 

[PTvor]

As I understand it, arc welding transformers have a lot of leakage inductance. That is, the windings behave a bit like two chokes and a bit like a transformer. As you more the moveable core section in, it increases the magnetic linkage between the coils and they behave more like a transformer, but the output voltage stays the same as the turns ratio is the same.

There are other ways of adjusting the output current, such as having a variable choke.

A MIG transformer is much more like the ordinary sort of mains transformer you find in a hi-fi say. If you short the secondary, it can produce huge currents, limited by the resistance of the windings and saturating the core. Saturating the core is going to produce problems for the primary, which starts to behave more like a piece of wire connected across the mains.

I think you are right in that it would hurt the rectifier if the rod stuck. You could bypass the rectifier and have an AC arc machine, but it seems like a way to waste a lot of time and wreck a working MIG.

If the idea was a flyer I think we'd see cheapish transformer based combined AC/DC MMA and MIG machines, and as far as I'm aware, there are none.