Hi. Thanks for a swift response!
The cutter is an RTEC P50HF, from R-Tech Welding in the UK.
I tried to post a link but the forum said I was a naughty boy and trying to spam it, so I've had to delete. Sorry.
There is a circuit diagram in the manual, on the page there.
The switch is a control signal, you wouldn't put a plasma cutter power feed through a button. I think the control is just looking for a ground, rather than a voltage.
I guess I am wondering if the board is fairly resiliant against interferance, and how easy it would be to use for this purpose.
I'm aware that shielding and grounding will be crucial, the cutter has a dedicated earth for attaching to CNC benches etc. I'm an offshore Survey Electronics Engineer by trade so routing out and nailing down interference is very much within my day to day work, so the usual things like removing earth loops, grounded cable shielding, twisted pairs, and sensible cable routing will be employed.
I also wonder just how I would actually use a duet as it has a superior spec than that of the black box, but OpenBuilds has some driving software for the blackbox controller that is already delveloped and there.
I don't really want to reinvent the wheel, I tried that once with a 3D printer and ended up with, more or less, an Anet A8 with a fancy frame.