CNC Plasma combined?

[GalaticDan]

Hi,

I've built a cnc router just fine. Now I want a larger work area, I'm thinking of starting again and building from the ground up. I have seen CNC routers offered on the web that have optional plasma cutting heads. After playing with the cnc router I've built with various wood substrates, I'm concerned about making one large machine, routing wood for 2 days over a weekend and then plasma cutting? I mean, saw dust gets everywhere and the last thing I want is a fire? So are these optional heads that people offer, generally fitted once at purchase time on the commercial machines? I've not build a plasma cutter before, is it worth seperating the machines out, one for plasma cutting metal sheet, another for wood cutting? Job wise, I'd probably get away with making one machine, is it safe? I've seen pictures of plasma cutters with sparks flying everywhere.

Thanks,

Dan

[diarmaid]

I dont have either yet and I dont have much experience but FWIW.

Im going to build two seperate ones because:

- From what I gather cnc plasma is VERY messy, and I dont want dirty plasma dust all over my nice clean wood parts.

- At some point you'll want to do both at the same time and it'll be irritating, aswell as uneconomical to have to switch between them. Down time costs money.

- Didn't think of the fire thing, but now that you mention it Im sure while a minor risk, it'd still be a risk.

I suppose its like everything else, and depends on your own circumstances. If your stuck for space, or want both capabilities without the cost of two full machines....

[massajamesb]

Don't have a router up and running yet, but:
CNC Routers need a lot of torque, and not as much speed, whereas plasma needs very little torque, but a lot of speed.
The whole fire issue would kinda turn me off of it, the money saved by not building a separate machine is negated (to me) by monthly fire insurance premiums.

[Torchhead]

A combination unit is like building a sports dumptruck. The design is a compromise. Before I had experienced builders to ask (over 5 years ago), I designed and built a router/plasma table. Believe me, the risk if fire is way down on the list of issues. You need to design a machine that is fast (300 IPM +) AND has lots of torque. The gantry to support a router with minimal flex is a lot heavier and and you have to be able to sling that mass around at 300 IPM while cutting plasma.

The biggest problem is the huge amount of dust and smoke plasma generates. The methods to control that are totally different than for wood. With routing the dust is generated at the cutting point and concentrated vacuum can take care of most of the problem. Plasma smoke (which has vaporised metal suspended in it) spreads under the material and wafts up through the cuts, around the edges and just about every place but the point of the cut. A water table helps, a water table up to the back of the material helps more, but even then some form of exhaust is needed.

After I started cutting steel I only went back once to routing on that table. It takes 30 to 45 minutes to swap out the cut types. Plasma (because of effective Torch Height Control and the tendency of metal to warp and twist, does not have to be perfectly level. Routing on the other hand does or you get some funky cuts. You need better accuracy for routing because even on decorative cuts where you have to make more than one pass any inaccuracy shows up as offsets in the cut walls. Plasma is lucky to hold .020 in accuracy due to the nature of the flame cutting and the wear of tips and electrodes.

I have come to the conclusion that plasma cutting should be done in a closed room/area with agressive ventilation.

I have my larger plasma table designed and in the time allocation phase (I'll start on it when I get time) and my current table will be turned back into a 3D router table since it has the accuracy and torque needed.


I know a lot of the quasi-commercial table mfgs sell combo units. It's what the customer thinks they need. Maybe for the weekend hobby guy it is. For a shop where you are trying to make money it's a less than sterling idea.

That's my story and I'm stick'n to it.

[massajamesb]

I stand somewhat corrected.
As I said, I don't have a cnc router, yet. I wouldn't think they would need huge cutting and rapid speeds, as the wood would start to burn after a certain amount of force and heat.
IMO, it would be best to build two separate machines. Just makes more sense.

[Torchhead]

The observation was that you need high speed and lower torque for plasma (no cutting forces) and the opposite for routing. That, combined with the increased mass of the gantry you need for routing, forces you to have to sling that big gantry around for the plasma cutting. Typical plasma cutting is done from 120 to 250 IPM while cutting with the normal router won't go much over 80 IPM. Since you can't easily shift gears for the two types of cutting your design has to incompass both.

[diarmaid]

So how about the design incorporating a small semi-automatic gearbox at each stepper motor for switching speeds, and design some type of modified-hydraulic operated-frankenstein-giant-automatic tool changer, which instead of changing tools, would change back and forth between a router and a plasma torch with THC. Wire it all up so you press one switch and everything changes automatically and adjusts itself in about 3 mins ??? That would be sooooo cool

[massajamesb]

Wow, Diarmaid. That is an excellent idea.
You first!
I am still trying to design a cnc that takes my place completely. I want it to do all my cad/cam work for me so I just turn it on and it runs my cnc for me.
j/k.

[diarmaid]

lol....Im going to pretend there was no sarcasm in that and just say...thanks for the compliment!

Im sure its possible, but would probably cost a bit, and involve some nifty engineering. Maybe when I have my solsylva machine built I'll try something like it just to see the possibilities! Hey!...if it works it could be sold as a modification kit!!

[massajamesb]

There you go. A perfect way to make your second million.
Sarcasm? me?
Again I say,Attachment 26112

A grand idea, nonetheless. I applaud you.

[Torchhead]

You still need the Automatic Cutting Surface Changer and precision auto-leveler. Oh and don't forget the Automatic Machine Fire Suppression System
(:-)

[thkoutsidthebox]

Originally Posted by Torchhead You still need the Automatic Cutting Surface Changer and precision auto-leveler. Oh and don't forget the Automatic Machine Fire Suppression System (:-)

Is that all? Spoilsport!....actually Torchead, you would be just the type of experienced person to design and implement something like this....