15m Industrial Plasma Cutter

What is the thicknes of the material to be cut ?
Asuming it is very thin, you will have to make the gantry very light, cutting thin materials with plasma requires very fast movements.
You can use the parallel port for that but considering the overall price you should really buy a Mesa 7i76E or at least a 7i96.
Also the price of Mesa THCAD is so low that you will regret not having it the second day of use, it is imposible to cut thin materials without it and making manual adjustments during cutting will prove way to dificult.
As for servo motors, use steppers, you will have to deal with a lot of interference and very long cables that might end up waisting a lot of time and unreliable machine.

You could make a machine with a single axis (+ THC) that rolled and unrolled the material under the cutter for the other axis, and with a simple run-out table.
It works for plotters and vinyl cutters. But those don't end up with any loose parts.

It would be neat and compact, but might not be able to move fast enough for thin material, as Tommy pointed out above.

I think that, for a first build, the roll-unroll and cable-bot ideas I have suggested are too untried, and a conventional gantry machine is the way to go. But there is no reason that it couldn't incorporate a coil feeder.

If you are going servos which makes sense given the size, I think you should forget about parallel ports and have a good look at the Mesa cards and add the THCAD-10 board which for $70 with the plasmac config will mean you have a high quality THC which you will need for the thin material for sure. $300 or so here is not going to break your budget.

I think I'd build 2 separate rails (say 100 x 100 x 4 SHS) that are mounted and aligned carefully that the gantry runs along and then build your down draft or water table as a seperate assembly that sits between them. That seems to be how the big tables are built. I'd go with rack and pinion drives and say 5:1 or so reduction drives.

Thinking out of the box here, you might be able to mount the electronics (and possibly even the plasma cutter) on the gantry itself and then all you would have is a mains cable and an ethernet cable to manage so noise on long cables would not be an issue. I don't have any wiring mounted to the table. Its all on the gantry!

The length of the table is not going to substantially add to costs

I would also suggest adding a 433 Mhz industrial quality pendant like I use.

And its not a big table by plasma standards. I have seen one 90 metres long.

The thinnest material to be cut is 8mm. The other is about 12mm.

I am planning to buy a Dell OptiPlex 760 and I am assuming that this will be able to run the program.

The company I work for has just bought a similar product professionally (pictures attached). It isn't cutting the same material and is a bit bigger but I notice that it uses servo motors, are you sure that steppers will be able to handle such a large device?

Also, does LinuxCNC interface with limit sensors (not just servo motor encoders)?

I was intending to mount the plasma onto the gantry, the current plasma cutter being used (by hand) is large and heavy but I was thinking that a more modern one could fit.



Thanks.

I don't think anyone said steppers. As Tommy said, keep the gantry as light as you can.
And yes, Linuxcnc supports max and min limit sensors as well as homing sensors. The gantry is squared during homing in software based on home offsets. I use PNP proximity sensors on the gantry for limits and homing. I have one shared home/limit switch on the Z axis

You'd really need to calculate some weights and see what size motors you need to achieve target velocity and acceleration.

There are some notes here
linuxcnc.org/docs/devel/html/plasma/plasma-cnc-primer.html

and also the plasmac manual
linuxcnc.org/docs/devel/html/plasma/plasmac-user-guide.html

I actually like the idea of having everything on the gantry... Say a 105 amp Hypertherm or 120 amp Thermal Dynamics is not that heavy and both would romp in with 12 mm. The Hypertherm has the advantage of amps and pressure being controlled by software except presently this would require a RS485 cable back to the PC but I think soon this might be able to be managed by a remote control card.