looking for the best way to build one of these tables

[chiliuno]

i'd like to build a cnc plasma table. i already have a good cutter (esab 1500), but i'd like to have something that works the way the plasmacam machine advertises that it will- auto height control, precision cutting, the works. i would like mine to have a 4x8 cuting area so i can use standard sheets.
what do i need? i see alot of opinions on here, but i want to get the best stuff around and not have to upgrade or get agravated with junk that saves me a few bucks but doesn't do the job reliably. i'd like to build this thing so i can learn what it takes to build one, and i'd like to save some money, but mostly i want to build it myself because i want to know how to fix it when it gives me trouble. i have the use of a plasmacam machine now, and it's great when it works right, but so far i've had more trouble with it than it's worth. it's probably my fault, but just the same i'd rather learn from the bottom up and take care of things myself.
any input would be appreciated, and specific directions would be really appreciated, lol. thanks!

[Javelin276]

I would recommend building your own, if you have access to some machine tools to cut the parts out on. It will cost about $1500 in motors, controllers, mechanical components, and some structural material if you are careful. I'm using an older 333mhz PC running EMC on Linux, mostly because it was all free. It works pretty well so far. That's many thousands less than a PlasmaCam. Get a couple of key friends to help, and it goes together pretty fast.

[chiliuno]

thanks for the response.
that's just what i'd like to do, i just don't know where to get started. i need to know what to do first- i'm thinking that i'll nuild the gantry first and install the computer/motors/software later.
anybody have a proven frame design that they like that they could tell me about? i can build pretty much anything but i'd rather use a plan that somebody else already made work well to avoid waste.
more input would be much appreciated.

[Javelin276]

Glad to hear you're thinking of building your own! Mine has been a real hoot. All I have left is to get the torch switch wired in so the computer can operate it, and I'll be cutting patterns out this weekend.

I put up five pictures of my gantry in the "Home Made CNC Machines" section titled "Javelin's XYZ Gantry" for you to look at just in case you're interested. It's a mid-range machine, bigger than the small routers, but simpler to build than most of the big gantries in the photo albums. It has a 4 ft x 5 ft work area, but a 4' x 8' wouldn't be much more effort. This one was sized to fit the available area in my garage.

My sketches are all on engineering paper, but I suppose I will eventually draft it all up properly anyway. My helpful friends would like to build the second one a bit faster once we get some cash flow off the first machine. I'm a mechanical robotics engineer, and my buddies include an electrical engineer and an ornamental welder.

A good place to start would be to get a basic table design in mind, then search for cheap sources of materials like the local metal scrap yard and army surplus stores. You'd be surprised what you can find cheap. The motors and controllers are probably best purchased new to fit the design you select. You will need to select a motor and control style as well. I chose steppers for simplicity and overall low cost, but servos are smoother and give you better performance.

There is another thread currently comparing ball screws versus rack and pinion you might find useful. Ball screws work great on smaller machines, but getting an 8 ft long one to behave can be challenging. I went with rack and pinion for that reason, and also because they can hit higher speeds and cost less.

Study all the pictures you can, then make your decisions and go for it!

Thor