QTPlasmaC with fourth axis - rotary

Has anyone implemented a fourth e axis for rotary tube cutting yet? I read some old posts that seemed to indicate that PlasmaC will not allow that. According to the Sheetcam tutorial, the THC will take care of cutting over the corners of a square tube.
I also saw something about QTPlasmaC having a setting to allow Z axis movements.
Can anyone shed some light please?
 

linuxcnc.org/docs/devel/html/plasma/qtpl....html#_keep_z_motion

That will do it then for the Z axis moves.
The only question then is can I have a fourth axis? Although it is a rotary axis but it is setup as a linear axis in order to accommodate the Sheetcam plugin requirements.

mariusl wrote:

According to the Sheetcam tutorial, the THC will take care of cutting over the corners of a square tube.

 

Yeah ... no!
At very slow turning speeds, yes
Made it work at normal cutting speeds, but required building a new Z axis with float switch that can do 6m/m at least, for it to be usable, for up to 60x40 oval, not square.
If you have a look at industrial 4 axis machines, they all have the tube stationary while cutting with plasma. Lasers are a different beast, so there are some that do cutting and moving at the same time.
All this can be done, it just complicates things a bit, and must settle on the main thing, what will the machine be cutting, from this to that, no "i would like to .. later".
Using 4 full axis absolutely works, the CAM is the issue there. SheetCam did have something for it, never used so no idea how good it is.
Also radius's cause issues, so must be accounted for.
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If we can agree on what we need the machine to do, say from 30x30 to 100x100 with 2,3,5 and 10mm radii, maybe we can convince Phill and Snowwy to make a wizard for it, for most uses the wizard is OK.
As for cutting complicated stuff on square tube, no need for 4 axis, cut one side, turn, repeat. We do this a lot.

Have a look at this video. It is using Mach3 at fairly high speeds. I am of the opinion that if they can do it in Mach, I don't see why it can not be done in Linuxcnc.
I unfortunately don't have enough insight into the inner workings of QTPlasmaC to comment at all.

Would be helpful to see their gcode file.