Stick welder -> plasma cutter?

[davesisk]

Hi folks:

Just wondering here, since a plasma cutter uses a constant current DC output power supply, is there anyway to turn a stick welder into a plasma cutter? Obviously, there has to be an airflow, but that seems pretty simple. Just get a plasma torch and add an inexpensive air regulator somewhere in the line (assuming that your compressor doesn't have an accurate regulator already).

I've seen some info about some older plasma cutters that were "touch start". Apparently, these gadgets had some sort of spring loaded contraption on the torch that, when you pulled the torch trigger, the electrode momentarily touched the nozzle then pulled away to start the arc. I guess then the arc would jump to the workpiece as you brought the torch near it? (This sounds a lot like scratch-start TIG, which I used my little inverter-based stick welder for prior to buying the ESAB Heliarc.) Has anyone ever used any of these older technology plasma cutters? How well did this "trigger-start" work?

Anyway, I've got a pretty decent little inverter-based stick welding power supply (80 amps @ 40% duty cycle, runs off 110V 20amp), and I'm wondering if it's possible to retrofit this guy to function as a plasma cutter? I'm thinking 80 amps ought to cut some pretty thick stuff, eh?

Thanks!
Dave

[Sberry]

Dave,,, dont quit your day job to become an engineer.

[davesisk]

Too late...I'm an industrial engineer by education, software engineer in practice.

I'm reasonably sure this is remotely possible. I've been told "nah, you can't use a stick welder power supply as a TIG power source, it'll never work"...but it worked quite well (they're both constant current power supplies, just had to scratch start and turn the gas on manually), and I even sold a few of those setups on Ebay. Any idea where I would find any technical data that describes the differences between stick welder and plasma cutter power sources? I've read that TIG and plasma cutter power sources are VERY similar, so the transitive property leads me to this possibility... I'd imagine the open circuit voltage might be quite different, but I'd really like to see some documentation on it.

Thx,
Dave

[cope]

Originally posted by davesisk
Too late...I'm an industrial engineer by education, software engineer in practice.

I'm reasonably sure this is remotely possible. I've been told "nah, you can't use a stick welder power supply as a TIG power source, it'll never work"...but it worked quite well (they're both constant current power supplies, just had to scratch start and turn the gas on manually), and I even sold a few of those setups on Ebay. Any idea where I would find any technical data that describes the differences between stick welder and plasma cutter power sources? I've read that TIG and plasma cutter power sources are VERY similar, so the transitive property leads me to this possibility... I'd imagine the open circuit voltage might be quite different, but I'd really like to see some documentation on it.

Thx,
Dave

Don't pay any attention to whoever tolf you that. There are quite a few Stick/Tig combinations around. Adding Tig to a basic stick amchine isn't the best way to do it, but it will work.

[dseman]

I see that you post your same questions on the aws board......

Plasma cutting power supplies are drooping type, constant current. The major difference lies in that the open circuit voltage is around 120-200volts for the PC and 60-90volts for the welder. Of course you will also need a high frequency generator and pilot arc relay contact. Get on google and start searching if you want to learn more....

-dseman

[dseman]

If you visit www.hypertherm.com you can find power supply data. Typically 300-350 volts for open circuit and 100-150 volts to support the arc in the plasma. I guess you need to start winding your own xfrmr.

-dseman

[Hobart Expert Dave]

Plasma and welding are totaly different. Plasma works with High voltage around 250 volts and low current around 12 amps for the small cutter and 60 to 100 amps for the large cutter. so the voltage is what is heating the material for the cut. As for welding the transformer is a low voltage arond 80 volts but the current is high up to 500 amps on some welders or better. So No you can not turn a welder into a plasma cutter.
Dave Evans