Rotary cutting square tube with PlasmaC?

robertspark wrote: Just looking at sheetcam now there actually is a LinuxCNC Plasma Rotary post processor listed:

If you look at onPenDown it requires a touchoff routine in a seperate gcode file. You can grab BigJohn's from here:
gnipsel.com/shop/plasma/plasma.xhtml

This will get you going but you can improve on this by probing back away form the material (check the gcode docs).

I put a magic comment in the QtPlasmaC gcode parser, so if anyone is game they can give it a try, it is called #<keep-z-motion>

#<keep-z-motion> = 1,  you can make z axis moves and qtplasmac will NOT make the initial Z move

#<keep-z-motion> = anything else, it behaves as existing

if it is not in the gcode file it means it behaves as existing

I have a feeling that a dedicated square-tube cutter could be completely passive, just a motorised chuck and a roller running on the tube to set the torch height.

Maybe only for straight cuts, though. But the fact that the chuck side of the tube is always supported simplifies things a lot.

And, anyway, where's the fun in that?

andypugh wrote: I have a feeling that a dedicated square-tube cutter could be completely passive, just a motorised chuck and a roller running on the tube to set the torch height.

Oh i did try that, and it did work quite OK for straight cuts.
I need them to cut up to 70 degree angles, and that might be good enough for this also, but then if i need to cut some shapes or slots ....

Tommy, sounds like you need my tangential update to Linuxcnc that Andy made me do that I never finished off.... it could rotate the roller to follow cut direction.

What about a ball bearing? You can get ones to slide material on...

rodw wrote:
What about a ball bearing? You can get ones to slide material on...

That was the general idea, if i could find them.