is it possible?

I have another post: http://www.pirate4x4.com/forum/showthread.php?s=&threadid=68276 showing where I got my on board welder and my on board air all hooked up, someone said now it is just time for the onboard plasma cutter.

my question is: is this possible? I would be interested in trying to do it if someone could point me in the right direction.. I know a plasma cutter is pretty much just a controlled leak, so how would I control it to start cuttin?

anyone?

Plasma cutting is a simple concept but requires fairly high toleranced and designed components and controls. Plasma cutting can take ordinary shop air and change it to its fourth state, plasma, which is blown through conductives to cut them. There is careful air metering through the nozzle, a venturi effect, power switching and ramping (oh yeah, this is DC too, not AC that is required). This is why they are so darn expensive.

I am not sure how you could even go about building a backyard plasma cutter without lots of time and money!

from http://www.plasma-cutter.com/technical.htm


Plasma cutters work by sending an electric arc through a gas that is passing through a constricted opening. The gas can be shop air, nitrogen, argon, oxygen. etc.

This elevates the temperature of the gas to the point that it enters a 4th state of matter. We all are familiar with the first three: i.e., solid, liquid, and gas. Scientists call this additional state plasma. As the metal being cut is part of the circuit, the electrical conductivity of the plasma causes the arc to transfer to the work.

The restricted opening (nozzle) the gas passes through causes it to sqeeze by at a high speed, like air passing through a venturi in a carburetor. This high speed gas cuts through the molten metal. The gas is also directed around the perimeter of the cutting area to shield the cut.

In many of today's better plasma cutters, a pilot arc between the electrode and nozzle is used to ionize the gas and initially generate the plasma prior to the arc transfer.

Other methods that have been used are touching the torch tip to the work to create a spark, and the use of a high-frequency starting circuit (like a spark plug). Neither of these latter two methods is compatible with CNC (automated) cutting.

The photo at right shows consumables from a Hypertherm Powermax 900 plasma cutter. The electrode is at the center, and the nozzle just below it. The orange piece above the electrode is the swirl ring, which causes the plasma to turn rapidly as it passes.

While these parts are all referred to as consumables, it is the electrode and nozzle that wear and require periodic replacement.




The part in bold sounds promising...

Okay, first person to build an affordable plasma cutter that can cut through say....1" steel, using OBA, OBW, and commonly available auto parts, with a few acceptable high $ components for saftey's sake.....

.....Shall be referred to as "Big Chief Large in the Pants King of all Wheelers Grand Exalted Pooh-Bah" for the next year, or until the next big thing hits the sport.

http://www.plasma-cutter.com/plasma_process.jpg

Initially, the electrode is in contact with (touches) the nozzle.

When the trigger is squeezed, DC current flows through this contact.

Next, compressed air starts trying to force its way through the joint and out the nozzle.

Air moves the electrode back and establishes a fixed gap between it and the tip. (The power supply automatically increases the voltage in order to maintain a constant current through the joint - a current that is now going through the air gap and turning the air into plasma.)

Finally, the regulated DC current is switched so that it no longer flows through the nozzle but instead flows between the electrode and the work piece. This current and airflow continues until cutting is halted.



Granted, this is a different starting method, you still need the air and power required precisely metered. Not saying it can't be done, but I can't see of a way of doing it cheap like an OBW.

Why not just use carbon arc rods along with your onboard air?

Originally posted by Scout Dude
Why not just use carbon arc rods along with your onboard air? Not enough juice from the on board welder.

Originally posted by Scout Dude
Why not just use carbon arc rods along with your onboard air?

That'd make the most sense rather than fabbing a scratch start PC. Now for the real question. why?

i can't think of too much cutting I'd need to do on the trail, why not just a damn hacksaw?


oh, and 6013 makes a good hillbilly plasma cutter at 225 amps :flipoff2:

TEAMRUSH doesn't visit this board, but the man knows his shit. He might just be "big chief" someday.

http://tellico.off-road.com/ubbthreads/showflat.php?Cat=&Board=offroadjeepshort&Number=826216&page=3&view=collapsed&sb=5&o=0&fpart=

Damn, sounds like we might have a winner, I could tell he was smart by first name alone. Have to keep an eye on this, not sure what I'd ever need a plasma cutter on the trail for, but I'm too cheap to by one for my garage, so If I can make one for the Jeep, well wo-ho! I'm there!

I saw a safe cut in half with a system called "Slice".
12V, O2 and a rod to start cutting. Full portable systems were ~$350. Small and compact, hardly seems worth the trouble or $ to build one.

Originally posted by hybrid
I saw a safe cut in half with a system called "Slice".
12V, O2 and a rod to start cutting. Full portable systems were ~$350. Small and compact, hardly seems worth the trouble or $ to build one.

looks like a nice litte unit.

Right page: http://www.cigweld.com.au/pages/images/catalogue/section2/2_CUTEQUIP.pdf

I'm not sure how much juice you need for Air arc, but it's sure fast, and you also get the windblast to blow the slag out. It's not that good for plunging, but you can blow through 1/2" fairly easily... As I recall, you do need alot of air, but you could probably figure out some sort of piggyback inductive sensing circuit that would open up an air solenoid ONLY when you're cutting. Ok this sounds way too hard already.

One thing - air arc is louder than the rapture, which automatically makes it super cool. It's as loud as thunder combined with jetwash.

Bob

That's it! I don't remember it being that loud but I was in total testosterone overdrive playing with it so mabey it was.
I cut a 3/8" plate 4" long and could put my hand raight on the plate and not even close to getting burned.
Then I used it to plunge drill a hole through a fireplace lining firebrick... OOOHH the testosterone rush..

Phoenix Welding Supply is where I saw it at one of their demos.
Anyway - GaJeep94YJ, it may be an option for you.

has anyone pursued this futher, sounds interesting.

http://www.brocoinc.com/

Check this stuff out.

MJ:eek:

Originally posted by hybrid
That's it! I don't remember it being that loud but I was in total testosterone overdrive playing with it so mabey it was.
I cut a 3/8" plate 4" long and could put my hand raight on the plate and not even close to getting burned.
Then I used it to plunge drill a hole through a fireplace lining firebrick... OOOHH the testosterone rush..

Phoenix Welding Supply is where I saw it at one of their demos.
Anyway - GaJeep94YJ, it may be an option for you. I'v been on fire air arcing, literaly. You need alot of amperage ( bobcats and traiblazers can't put out enough juice) and alot of air. As far as air arcing on the trail, you would need serious containment of the spray. Use 6010 3/32 rods and crank up your obw, it'l be messy but it'l work. My 2c

My two cents:

:eek: portable oxy/acetylene (NOT PROPANE) torch:eek:

Cut (damn near anything, WITHOUT ALL THE NOISE) , braze, weld, bend/or straighten< depending on your lead foot ,etc.

All that for just a couple hundred :)