Rotary cutting square tube with PlasmaC?

I'm building a couple of new machines, one of which is a 4 axis rotary tube cutter with RPI4 2.8.1 and 7I96.

As a novice level LCNC user I am wondering would I be better off not installing PlasmaC on the tube cutter and instead use Sheetcam rotary plugin & postprocessor with the base machine config to control the Z axis?

You will need to use PlasmaC, sheetcam and post-processor can not control Z axis during cutting, using both will be the best solution.
I am pretty sure you can use it without PlasmaC and THC, but any misalignment will end up with the torch dragging on the material or not cutting at all due to it ending up to high.

here is a recent post from Les at sheetcam on rotary + square tube (4 axis recommended, you can normally get away with 3 with a rotary axis as you can repurpose one of the axis to drive the rotary motion device stepper)

forum.sheetcam.com/viewtopic.php?f=2&t=8458#p28054

THC is best left off and run blind (no height control) with the z being controlled by gcode.

just something to consider, best ask Les if you have any questions about it / his thoughts on the subject

robertspark wrote: here is a recent post from Les at sheetcam on rotary + square tube (4 axis recommended, you can normally get away with 3 with a rotary axis as you can repurpose one of the axis to drive the rotary motion device stepper)

forum.sheetcam.com/viewtopic.php?f=2&t=8458#p28054

THC is best left off and run blind (no height control) with the z being controlled by gcode.

just something to consider, best ask Les if you have any questions about it / his thoughts on the subject

It would be worth testing to see if the Plasmac THC can lift the torch fast enough to follow the surface. If you have a good Z axis, I think it would be able to do it without crashing. say you are cutting at 2000 mm/min, my rough calcs says your Z would need to accelerate at 1000 mm/sec/sec to follow it. But I'm a horrible mathematician!

rodw wrote:

robertspark wrote: here is a recent post from Les at sheetcam on rotary + square tube (4 axis recommended, you can normally get away with 3 with a rotary axis as you can repurpose one of the axis to drive the rotary motion device stepper)

forum.sheetcam.com/viewtopic.php?f=2&t=8458#p28054

THC is best left off and run blind (no height control) with the z being controlled by gcode.

just something to consider, best ask Les if you have any questions about it / his thoughts on the subject

It would be worth testing to see if the Plasmac THC can lift the torch fast enough to follow the surface. If you have a good Z axis, I think it would be able to do it without crashing. say you are cutting at 2000 mm/sec, my rough calcs says your Z would need to accelerate at 1000 mm/sec/sec to follow it. But I'm a horrible mathematician!

2000 mm/sec do you mean 2000 mm/min :ohmy:

I saw that post about a month ago when Tom said something about cutting square tube.

Do you think Les was talking about a 4th axes in terms of one rotating the torch as it rounds the corner?

Told you I was horrible with maths!

But I'm not sure Les is right here.

If you have THC this also guarantees that the torch will crash into the work.

I would calculate the perimeter distance which you can do if you know the tube dimensions and the corner radius and just cut it as if was pipe. I think the Plasmac THC would look after the rest.

I've not tried it but I think in CAD, you could cut a 0.001mm slot in the square section, convert to sheet metal and flatten the pattern to create a cuttable unwrapped DXF.