Can someone explain a plasma table to me?

[jimluu]

Hi, I've new to cnc in general. I've planned on building a 3 axis router, and would like to be able to do some plasma cutting as well. Could some one explain what the fundamental difference between the design of a 3 axis router and a plasma table is? thanks.

[Torchhead]

Better go back through a lot of threads and read about the dust, smoke and fire that plasma generates. There is a lot more to it than just strapping a plasma cutter to a gantry and hitting the RUN button. Everything from the artwork to the cutting surface is totally different than routing. It is a neat process when you get it set right and watch a 30,000 deg flame slice through solid steel plate like a butter knife. Things can go bad in a hurry and you really do need to understand the plasma cutting process pretty well. A lot of the problems guys have with plasma cutting is they have never cut with a plasma torch or understand how it works or even why all of the parameters are critical. Things like pierce height, variable pierce delay, initial cut height, Torch Height Control, tip volts, tip gap, feedrate, cut flare, lead-ins, kerf-offset, anti-dive, constant velocity cuts are all important for good results.

CNC plasma cutting can be a profitable business but it can also be a source of frustration and lost money if not done under controlled and precise conditions. The result is not precision (in the machinist's world) but the approach needs to be.

The difference in design in the table boils down to this:

Plasma needs needs speed (up to 300 IPM). moderate resolution, good acceleration and is non-contact with a light load. The gantry can be light and not have to worry about any twisting forces as it cuts. The slides can be lighter duty and the motors can be smaller and geared higher. Loss of resolution is not as critical.

Routers need torque (opposite of speed), good resolution, moderate acceleration and is contact cutting with a heavy loading factor. Router gantries tend to be bigger and heavier to handle the cutting forces of the router and it's mass being slung around, and to combat racking and torsional forces (including the twisting forces along the gantry from the cutting tool) The Z needs to be more heavy duty both in the slides and the lifting capability.

It is the difference between a dump truck and sedan.

To build a muliti use table you have to build a table that is Fast, high torque, high resolution, high acceleration, heavy gantry, stouter Z, and easy to convert from one to the other cutting surface.

You have to build a Dump Sedan.

My advice: If you want to cut out a few parts now and then either find a buddy with a plasma table that you can trade time for some routing, or cut the pieces by hand.

Tom Caudle
www.CandCNC.com

[jimluu]

Thanks very much tom. That's exactly what I needed to know. I'll probably buy one of your kits in the near future. thanks again.

[millman52]

Biggest thing to overcome for a dual purpose plasma/router table would be the cleaning up of the plasma black & grit to keep from staining or fingerprinting every piece of wood you turned out. The dust, grit, soot or what ever term you care to label it with is very hard to get completely cleaned up. Not only the machine but every surface around it you might touch before or during a router job. The black would get on your hands then transfer to freshly milled wood.

Never tried it, but I have tried keeping a couple pieces of wood working equipment in the same shop as metal working machinery. That really doesn't work either. At least not without cleaning a couple days first then a couple more days of cleaning wood dust up after.

Just my 2 cents.