make a plasma machine-torch?

[Tony]

greets all.. work is progressing on the CNC plasma table.

I'm surprised to see how much machine torches cost!

I have no experience with a machine torch.. but am quite familiar with a manual plasma torch.

anyone know how hard it might be to make a machine torch? or can tell me anything about them?

-tony

[Ries]

Plasma machine torches cost $500.
Doesnt seem like a fortune to me, but I have only bought two, and the first one still works- it just doesnt work with my current power supply. Life span for them seems pretty indefinite. I have thousands of hours of use on my current one.

Certainly not impossible to make one- they are vertical in format, instead of a right angle like a hand torch. Obviously you want to use the guts from a hand torch that you can get consumables for. Then make your own cylinder to mount them in, with a rack screwed on the side for up and down adjustment.
Mine have both been made from a heat resistant plastic- some kind of fancy fiberglas, I think. Cast, then machined.
You should be able to download a schematic free from one of the big suppliers- I think hypertherm and plasma dynamics make the best torches, so I would copy them- just go to their websites, and find the manuals for machine torches. Worst case, email them and have them email you the manual and schematic.

[Tony]

Ries,
thanks for the tip. in these neck of the woods, though, any machine torch i could get consumables for (at a reasonable price) is about 900euros (~$1200).

checked the Hypertherm site and all i find is breakdown for marchine torch consumables.

makes me wonder, since i'd be using the same inverter-plasma cutter (1/2" capacity), you think a machine torch would even be worth it?
-- i could water cool it, but i'm wondering if that would change the duty cycle any, in the box.

-tony

[KENZ]

I'm not sure exactly what you are looking for but maybe this site can help.

http://www.plasmacam.com/

[ibewgypsie]

Guys, I am working on a trolley system for a friend. Using inline roller skate wheels running in track, cable drive. YOU can use really small stepper motors since the friction/mass/weight of the torch is not high at all.

I need two more pieces of aluminum stock to complete it. Then, since I am using a discarded calcomp plotter I will have to figure out how to calibrate it. Pretty neat so far, about $30 invested. I am using the factory stepper drives. Non-regulated Speed should be comparable to a plot.

My cnc bridgeport has been successfully hooked to a cutting torch and a plasma cutter with no problems, cutting size is limited to the table stroke of 18"x8".. Also the room my cnc is in I have books on the shelves that I worry about setting ablaze.

A plasma table can be light enough to set on a barrel head, or set onto a sheet of steel, fastened to the steel by magnets. I have three of the release style pick-up magnets from Harbor freight I have considered using.

End result? streetrod parts I can ebay. It is starting to get hungry around here. (damn attorneys)

David

[Ries]

Like any tool, how stout you build it depends on what your expectations are.
Ibewgypsies mini plasma cutter, magnetized on a piece of steel, will work fine for the scale of work he wants to do.
I often cut 4x8 sheets, or even 5x8 sheets, of 3/16" or 1/4", so my whole setup needs to be a little bit heavier duty- strong enough to hold the steel, and get bumped by the forklift loading the steel. And dumb enough so I can teach a new employee how to run it in an hour, and he can run it for 6 hours with no fiddling or mysterious fixes only I know.

As far as a machine torch goes- I think watercooling is overkill for less than a couple hundred amps, running all day long.
I run a thermal dynamics Pak 75, and we can cut 1/2" plate for hours with no problems with an air cooled machine torch.

The cheapest approach is to go like the plasmacam, linked above, and just make a clamp for your hand torch. There are two drawbacks to this- first, you have a harder time adjusting the height of the torch off the sheet. This is not a real big deal- its just handy to have a rack and pinon drive when you are using it a lot, and running big stuff in and out often.
Second, a real machine torch has no switch on it- it is turned on and off by the cutting machine, remotely. You can just put a hose clamp over the switch on a hand torch, so it is always "on" then switch it at the machine- it will work.

I didnt realize you were in europe- 900 euros? man, thats a lot of money. I suppose you could mail order one from a big internet welding supplier over here- doesnt weigh much, you could have it air shipped for not much- but then you would have the consumables problem- and have to order them by mail too. Sometimes I buy CD's from Amazon UK that arent available in the US, and freight is usually under 10 bucks for fed-ex, so I cant imagine it would cost much to ship an envelope full of tips and nozzles.