CNC Plasma Table

[Colten Edwards]

I'm about to embark on a new CNC project.. I have my electronics (ethernet smoothstepper, Gecko G540, CNC4PC breakout board for the smoothstepper and 270oz/in nema23 motors). Ordered some rails from China. These are heavy rail as I'm used to the mgn12 rails used in my 3d printers. Price was pretty good for 3 1500mm rails and 6 bearing blocks it was just under $200 shipped. Bought a proma THC150 plasma controller as well (controls the Z height according to the voltage on the plasma). Currently shopping for 2in square tubing but because of the holidays haven't heard back from VarSteel. Need about 60ft of it, so princessauto ain't happening. Have some 6" wide 1/4" CRS coming from traverscanada. And got a crapload of stuff coming from china. Belt's, pulleys, sensor's etc which I don't need at this time.

Now I need to decide if I'm going to TIG or stick weld or purchase a tank of C25 for the mig welder and hope it still works. Mig was a freebie from my father. The TIG is new and I'm not anywhere near proficient at it. It's a Everlast 256SI which I purchased earlier this fall. It has plasma in it as well which I hope to use to start out cutting with.

As I start this build I will take pictures and upload them here.

 

[kevin.decelles]

Any thoughts on software? (mach vs linux vs other?)

 

[kylemp]

I've built one of these before, although using 1/4" CRS as the bearing rails and I made trucks..
I don't know how well the smoothstepper will work, it should be fine. I use a G540 for control, which takes a DB25 connection so it can run directly from parallel although I'm sure you can make up or buy a cable from the smoothstepper/breakout that goes to it. You pretty much MUST have a THC, although I've heard mixed stories on the less expensive ones, I used an old one (not sure if its even still for sale, https://www.candcnc.net I think is where I got it). Consumable life really depends on maintaining the correct offset height of the torch, speed and pierce settings.
I had an arc welder when I built mine, and I had to borrow a MIG from a friend at the time which was absolutely required. You'll want a MIG, its much faster and cleaner, and even a TIG in certain spots probably.
I ran Mach3, but I have plans to build a couple more in the coming decade (hopefully sooner, but I'm pretty slow at projects) and I'll likely be running linuxcnc on the ones I make in the future.
If you haven't planned for it, you'll want a water table. They're very gross machines to run without water, and it puts steel dust into the air which is NOT good for you without water below to trap it.
Another thing when building - Make sure everything is VERY rigid. Plasma isn't like rotating tools, if there is vibration in the machine when cutting, it WILL show up as poor cut quality.. and the speeds that you generally cut thinner materials (I ran around 2.5m/min on 1/8" a36 plate because thats the maximum I could reliably get a good edge) cause whipping if there is any slop. You'll also need to learn about constant velocity (CV) mode for your controller - again, its not a rotating tool so if you slow down to get to a corner, it will just eat more material and screw up your consumables.
Just things that I learned over the years of building and running mine.
I sold mine a few years back, and ever since I've been missing it. They're incredibly productive machines to have, although they take a bit of tweaking to get working just right. If you have questions post them here and if I can help I will.

 

[Colten Edwards]

with a smoothstepper I'm limited to Mach. I have both Mach3 and 4 licenses including the industrial license. In order to use linux, I'd have to replace the smoothstepper with either a parallel port or possibly a Mesa board. I've got one in my mill configuration and they are nice boards (running pathpilot). What I like about the smoothstepper is the isolation of ethernet as well as having a couple of spares if needed.

 

[kylemp]

I've never had any issues with backfeeding power if that's what you mean by isolation. I had 2 parallel ports in mine, which was enough i/o to run the machine but a bit more would always be nice.. I'm intending on getting a Mesa setup this spring to use, they're supposed to be incredibly versatile and fast, but that generally isn't an issue for plasma. Are you planning on driving this thing with screws or rack and pinion?

 

[Colten Edwards]

actually belt drive. 10mm wide GT2 belting with 12 tooth pinion's. I've been watching "Making Stuff"'s video's on youtube and this is what he used. Rack and pinion is a possibility if the belt drive doesn't work.. I have a 7i92H board from Mesa. Nice board, you do have to pay attention to the "bit" file you upload to it and make sure it matches your BOB. Or funny things can happen.