Convert an Econotig to a plasma cutter???

[alanaker]

Anyone ever do this? What do I need to do, and what would it cost?

[fun4now.]

what on earth would posess you to do something like that??? plasma cutters are way down in price just buy one. even a cheap import would likely work better.

[slamdvw]

*MY* guess that OCV ( open circuit voltage ) would be too low to initiate an arc (..plasma). Quick and dirty, some 6010 ( or is it 6011 ) rod can be used to cut, but from what I hear it's pretty nasty.

Or if you adventurous (sp) you could possibly air arc it to cut. Again, quick and dirty.

...then again just a wild guess ( way wild, mind you )... cheap plasma torch, air supply, ... and a way to initiate the arc... ( bbq 'click' lighter ). That works for a poor mans "tig arc starter"... of course, your mileage may vary.

But, i'd have to agree with fun4now, Get a plasma cutter and don't look back, you won't regret it. ( I didnt )

[pulser]

99% sure this is not feasible, hope someone else can explain exactly why.

But, in a pinch you can "cut" thin stainless steel (<1/8") with your TIG.
Crank up the current, use the smallest cup size, and crank up the gas flow.
This will melt and blow through in a crude cutting action.
If you are very steady in travel speed the cut can be very clean on one side of the cut. You can try tilting the piece to be cut so that the melted dingle berries collect on the downhill side of the cut, and the uphill side remains clean.
First saw this being done in a small production shop making SS vacuum chambers back in the 70's, when plasma cutting was rather rare and expensive. Have since made several brew kettles from SS kegs by this method.

[fun4now.]

slamdvw how would you start an arc with a BBQ striker ?? there is no flamable gas or even a flame involved in TIG or plasma cutting.

[slamdvw]

don't have to be flamable. I read about it searching for information on TIG welding. Tried it, seems to work OK. My setup involved putting the bbq lighter on the tig torch, about a 3 foot piece of 22ish ga wire from the lighter's ground to workpiece, and about a 8 inch or so from the business end of the ligher to the cable connection inside my tig torch.

The High voltage created will jump about 1/4 inch gap. ( use of auto darken helmet is a blessing here.) Start gas flow, position tip 1/8 or so inch from work, reach over with other hand and press the button.

[fun4now.]

ok i get it now you are talking about a electric BBQ starter and using the HF from it to start the acr just like the welders do on AC when they hF the start then drop off. for some reason i was thinking of a flint lighter like in O/A dont have any idea how i got there its just what i was thinking about. some times the noodle just wonders around and stops where it wants. LOL

[Grahame]

A quick comparison.
Tig arc up 6000 C it melts metal 80 volts open circuit

Plasma possibly 100,000 C, it vaporises metal. Can't remember exact plasma current but trust me, it lots - in the burn you big time league.

This is not intended as a flame- hopefully a caution so no one gets hurt through lack of knowledge.

have a good one mate
Grahame

[alanaker]

O.K.- I guess I need to understand how these plasma cutters work. I was guessing I could remove the TIG torch, and install a plasma cutting torch in place of it. Wondering if the Econotig power supply is good enough. Seems beefier than plasma supply. What kind of voltage (and polarity) is used on a plasma cutter?

I would rather sell or trade the Econotig but if it's going to be hanging around, I might as well see if it is adaptable...

[MicroZone]

Here is the quick answer - call Miller and ask them if you can adapt it. If not, sell it and buy a Plasma.

[fun4now.]

i would just sell it and get the plasma cutter that fits your needs. if it was as simple as just changing uot the torch, plasma would be an available option an all TIG units strait from the maker. wile some are dule purpose TIG and plasma they have seperate controle circuitry built into it to alow for both options.
sell the econo TIG, take a look at what you intend to be cutting and get a plasma cutter size apropreate for what you need.

[pulser]

Hey, someone here ought to be able to explain why a TIG power supply will not function as a plasma cutting power supply. I'm guessing the operation amps/volts are much different, otherwise we'd all have a combo TIG/Plasma cutter.

[fun4now.]

why should some one here be able to explain it?? you would need some one with an electrical engenearing degree that specilises in welding controles. most of us here are just welders, some hobiest some full time, and some that just started to be able to make stuff for fun or buisness. if you want a better anser call a welding comp like was suggested above, but odds are they will just tell you it will not work and not see the need to go into exact details as to why. i supose you could buy a dule unit and take it apart and see whats in it, but again still better and cheaper to just buy what you need.

[DesertRider33]

I dont know about the Econotig power supply, but PowCon used to make a plasma cutter that had no internal power supply and was intended to be hooked up to the outputs of their welding power supplies. As I understand it, I could use my PowCon 300SM DC mig/stick power supply to power one of their plasma cutters. I dont see what is so different about my PowCon than any other DC/CV welding power supply except that mine is an inverter, but there are plenty of inverter welding power supplies out there these days so I think it should be possible to use a welder as a power supply for some kind of home-brewed plasma cutter. The multi-use machines I see that are plasma cutter and welder in the same box probably use the same power supply section for both processes....

[fun4now.]

true you can use the same power suply but its not as simple as just switching out the torches. you need to add the apropreate circutry to get the right volts VS amps to do the job right. so i supose you could build up a controle circut board to do that to the econotig but you would need to know how and would probly spend more than its worth in the end.
best to just put a fresh coat of paint on the old econ and sell it. or maybee give it to a yungster in need of a welder, if ya know one or have kids. eather way i just dont see it as practical to try to convert it.

[awright]

Plasma cutters apply much higher voltages to the torch than TIG machines. I don't know the exact voltage, but I believe it is in the 180 volt neighborhood. TIG power supplies (and other manual welding power supplies) are limited for safety reasons to about 80 Volts open circuit.

The plasma power supply voltage is not regarded as an electrocution hazard because the high voltage is limited to the inner tip of the torch and is only active after a time delay following trigger actuation. Someone would have to be pretty determined to injure himself to grasp the tip, pull the trigger, and continue holding the tip as a high velocity gas jet hissed between (and possibly into) his fingers until the high voltage was activated.

Dual purpose machines are a relatively simple evolution from inverter welding power supplies because the manufacturer is already building a sophisticated inverter controller and it is a small step to provide additional windings on the inverter transformer for the higher voltages and the additional circuitry required for a plasma cutter.

Since the input portion of an inverter welder is a line rectifier and an energy storage capacitor bank, that portion could be replaced by a conventional DC welding power supply (requiring, however, some compensation for variable voltage from your welder and probably a capacitor bank that is not required in a simple DC welder). But then you have to build the inverter controller electronics, provide the expensive power semiconductors (MOSFETS or IGBTs) and the inverter transformer, which is the hard and costly part of the plasma cutter. The Econotig has no energy storage capacitors so you will have to supply those, also. So having done that you now have an expensive plasma cutter accessory that costs as much as and probably more than a stand-alone plasma cutter (because all you have saved is the line rectifier and it will be a very low production item so you lose the economies of scale) that is tied by an umbilical cord to your DC welder. Doesn't sound like an attractive option to me.

But try it out. We'd all love to see a successful adaptation.

awright

[comp]

lurking

[MotoFab]

Originally Posted by alanaker

O.K.- I guess I need to understand how these plasma cutters work. I was guessing I could remove the TIG torch, and install a plasma cutting torch in place of it. Wondering if the Econotig power supply is good enough. Seems beefier than plasma supply. What kind of voltage (and polarity) is used on a plasma cutter?

I would rather sell or trade the Econotig but if it's going to be hanging around, I might as well see if it is adaptable...

Hey there Alan -

If you want to give it a go . . . here are a couple of initial things to consider.

- There will be research and testing for you. That takes time and a few dollars.

- A willingness and ease about risking damage to a newly purchased torch is useful.



From my perspective, I think the reason a plasma cutter power supply has a high open circuit voltage has more to do with the economies of building the supply as inexpensively as possible. Not that there is anything wrong with that.

The reason I'm saying that is that once the arc starts, the arc voltage IS the power supply output voltage. It does not seem reasonable that 100 volts is necessary to maintain an arc length of one half inch say. Sure, the HF/HV starter circuit can start an arc a good distance from the work.

So Alan, if you want to walk through this, we can give it a shot.

I am sure the shills are watching, you may even be one

- Jim

p.s.: How did you do at the boat races?

[slamdvw]

It'd be handy to have both machines available for testing purposes. By this I mean finding one in a scrap heap, or landfill ( you'd be surprised at what people throw away!! ) Im sure a plasma will be a bit tougher to find, but I can find welders all day long at the local recycling yard...

Another option would be... have someone measure the voltage and current of your welding machine while you're running a bead. That'll give you an idea, loaded and unloaded.

Do the same with a plasma cutter... ( standard warnings apply, high voltages, high currents, capacitors, other nasty stuff,... you get the idea, you've been warned ), if your meters can read high enough, starting voltage, 'pilot voltage', loaded voltage and current, etc..etc.

As motofab put it, the willingness to spend some money, cause no doubt something will get destroyed. Judging that a welder is a high current, low voltage machine, I'm guessing that it'd survive.

Im all for experimentation, that's how a LOT of what we use today was invented or discovered. Im all for it, just can't afford to experiment as I'd like to.

Check scrap heaps, landfills ( if you can scrounge their piles ), ya never know, might just get lucky and find the necessary parts.

[fun4now.]

might find one that works with a fuse replaced 8^))

[alanaker]

Thanks for all the constructive replies on this thread!

Now that I've read up a bit more on how plasma cutting works, it makes sense to me to pretty much just not do it. Some said that initially, but now we at least know why. So, I'll most likely acquire a plasma cutter as soon as I can. I've noticed a couple of decent deals on Ebay recently. Should I stay away from the older ones? I'm sure someone out there locally can end up with my Econotig for a good deal.

I did manage to get that modified Mercury racing outboard together. My kid and I loaded up the race boats and motors and we went up to Maine last weekend. Saturday was windy and rough but we ran anyways. Sunday was much better. My "new" motor ran awesome and made one Ell of a lot of noise. There were 2 other mod motors there, plus a bunch of other "stock" motors and hydroplanes and a couple of runabouts. I do have a few pictures, and also a short video taken from a digital camera of a friend falling out of his hydro (he was o.k.) on Sunday in a race. These were unofficial races, not the regular APBA sanctioned stuff. Sort of a season ender finale get-together.

[pulser]

quote: "Another option would be... have someone measure the voltage and current of your welding machine while you're running a bead. That'll give you an idea, loaded and unloaded."

I can tell you that a current of around 150 amps, with Argon and an arc gap of around 1/16", the TIG welder will run about 10 to 12 volts (measured at the power supply). Don't know any data on the plasma cutter.

[MotoFab]

Originally Posted by pulser

I can tell you that a current of around 150 amps, with Argon and an arc gap of around 1/16", the TIG welder will run about 10 to 12 volts (measured at the power supply). Don't know any data on the plasma cutter.

Arc voltage is an interesting topic pulser, and is very relevant to fitting a plasma torch. Thanks for posting.

You measured 10 to 12 volts for an Arc Length of 1/16" in Argon. That's what it'd be. That's the only voltage it could be.

Argon gas has a specific Ionization Potential just like it has a specific molecular weight.

And, the Ionization Potential (call it voltage) for Argon is close to Oxygen and Nitrogen.

So-o-o-o . . . . the Arc Voltage for a plasma cutter electrode (or stick electrode or MIG wire for that matter) will also be 10 to 12 volts for an Arc Length of 1/16".

What can change the arc voltage? Arc Length.

Using a piece of scrap, if pulser pulls the electrode back from the work a little more, to make an Arc Length of 1/4" say, then the voltage he reads with his voltmeter will rise. Well, it will if the supply is capable of making that voltage at that amp setting. If not, the arc will go out.

If the supply cannot make that voltage at that amp setting, then he can turn the amperage down until it can hold an arc at the example length of 1/4". Maybe he will do that experiment for us.

(For clarification, I do not mean reading the voltage display on the front panel of the welder, but the DMM or voltmeter that pulser used to take the measurement.)


* * * * * *

Every 'arc process' behaves the same way. If the Arc Voltage for a TIG electrode is 10 to 12 volts at 1/16", then the Arc Voltage for a plasma cutter electrode (or stick electrode or MIG wire for that matter) is also 10 to 12 volts for an Arc Length of 1/16".

Do you see this? The voltage required to hold some particular Arc Length in any given arc welding (AW) process is the same.


* * * * * *

But a Plasma Torch operating from a TIG supply, how can that be? It'll never work the open circuit voltage of a plasma torch is too high. etc.

The Arc Length of a plasma torch electrode to the work is about the same as for all the other Arc Weld processes. And the voltage required to make that arc is also the same.


* * * * * *

Then why is the open circuit voltage of a plasma cutter so high?

Here is a way to understand that The voltage regulator that regulates the open circuit voltage in a TIG welder say, is sort of a practical necessity, not an absolute necessity.

Consider that arc voltage of a stick welder is regulated only by the welder's hand holding an arc length. And a MIG arc voltage is also typically regulated only by arc length (via the wire drive).

It is a fact that any type of power supply has a maximum open circuit voltage. It is a practical convenience however, for a TIG welding supply to have a regulated and adjustable maximum open circuit voltage.

But a plasma cutter power supply does not need a regulated maximum voltage, and in certain cutting instances a lower maximum voltage might be an inconvenience.

This is why I'm saying from my perspective, the reason a plasma cutter power supply has a high open circuit voltage has more to do with the economies of building the supply as inexpensively as possible.

If a regulator circuit isn't needed or wanted, then putting one in is a needless cost to the manufacturer.

And if having a high open circuit voltage makes it appear as though the various welding process power supplies are very different from one another, well that's all the better.


* * * * * *

Will it be as simple as hooking up a plasma torch to a TIG supply? May be. There is no reason why it couldn't.

I mean, the gas valve in the TIG supply can be set for post flow, just like on the Plasma supply.

What about pre-arc? I don't know if the 'plasma gas focusing' channels inside of any particular torch would work better with pre-flow, no pre flow, or a gas flow that starts a moment after the arc initiates. But that is discovered easily enough by examining the operation sequence of the plasma supply for the prospective torch.

That and a couple of other things like verifying the gauge reading on the pressure regulator in the plasma supply.

I for sure cannot tell from the advertising, maybe someone with an ET can chime in. Does the EconoTIG initiate its arc with a spark? If so, what sort of distance will the spark jump to the work? And, does the supply automatically attempt to reinitiate the arc if it goes out?

- Jim

[awright]

I agree that the voltage across the plasma arc is determined by the properties of the gas in which the plasma is formed and the length of the arc. However, I think it is a mistake to assume that the TIG arc is about the same as the plasma cutter arc. The cathode of the conventional home or small shop plasma cutter is up inside the torch, not at the visible torch tip, and the anode is the workpiece. Without running down and clamboring over my stacked stuff to find and disassemble my plasma torch, I'd guess that the cathode is, perhaps, 1/4 inch or more back from the visible tip. This makes the plasma arc longer and the voltage higher than for a TIG arc. This higher arc voltage may make the supply voltage necessary for a plasma cutter higher than is required for a TIG welder. I have no guess at this moment what the exact voltage required for achieving a stable plasma cutting arc might be, but it will be higher than TIG.

I disagree that the reason for the higher plasma cutter arc voltage is due to the desire of the manufacturers to make the machine cheaper (although they are certainly always striving for that). Consider that both the inverter welder and the plasma cutter typically rectify the raw line voltage, store the DC charge in a capacitor bank, chop the stored energy into an AC waveform of the desired duty cycle, pass the AC through the inverter transformer, rectify the AC waveform to DC (in the case of a DC welder or a plasma cutter), and apply the DC to the welding or cutting task. Both machines will simply rectify the incoming line voltage and process it for the end task, so I fail to see how the output voltage of the plasma cutter power supply affects the cost of the power supply. Both machines will transform the chopped waveform to the voltage/current required for the specific task at hand, and that voltage transformation is simply a matter of the number of turns in the secondary winding.

Sure, there are costs associated with the choice of output voltage, but I don't think they select the higher voltage of the plasma cutter to create a cheaper machine. I may be naive (although I yield to nobody in my degree of cynicism regarding manufacturers pricing strategies), but I believe that the plasma supply voltage is selected for stable arc characteristics, not for cheapness. For a given power rating, I would not expect the voltage to have much influence on machine cost.

awright

[slamdvw]

Just a hunch, higher voltage supply translates into lower current ( remember ohms law )... heavy copper windings ( or aluminum ) mean higher cost. They can get the same kVA rating out of a high voltage transformer as a low voltage unit.

This is an interesting thread... I'll hafta measure some voltages.

I know my Miller 375 does not like it's tip touched to the workpiece, namely after the main arc is established. It seems to like it if you touch it when you pull the trigger, you better keep it touched. And same if you have a stand off when you strike it...

... heh, wish i could find a plasma torch in the recycle yard... i'd put this myth to bed.

Im just guessing that the higher voltage is used to initiate the arc. If I knew my volt meter would survive it ( might just have to try it, theyre cheap ) I'd read voltages from my plasma... looks like i have a project this weekend.