Rotary cutting square tube with PlasmaC?

Since i have built several tube cutters for round tube, they are 3 axis machines and LinuxCNC does not care much that one of the linear axis is actually a rotary one, it works perfectly, and there is no need for THC at all if everything is set correctly.
But square tube has sharp corners and that messes up the material speed a lot making the use of the 4th axis a must, but again can be used without a THC.
I did test using a 3 axis to cut square tube, and it does work if the Z axis and THC are very fast, but not good. It will have trouble on the upslope and downslope as the material will be at a very sharp angle and moving faster than when cutting the side. And cutting any kind of design features messes the dimensions badly.
I have to build 2 of the square tube ones and will have to be full 5 axis machines as i need it to cut at an angle on some parts, the torch will have to rotate ....
Still no final design, but usually i do the design in my head and change it several times during the build.

interesting

would like to see an economic and practical bevel cutter 5 axis. (not in need of one just it would be great to it done by someone other than the big boys)

Some years back had a mock up as a proof of concept, it is doable and frankly mechanics are easier than the CAD/CAM part, but i just wing it in gcode as it is much easier for me to calculate a 1000 things in my head.
The main point of failure for this type of plasma cutting/bevelling is the simple fact that when cutting a 10mm thick plate at 90 degree it has to go through 10mm of metal, but at 45 degrees it has to go through 14.1mm. That goes higher exponentially with angle.
Hence the failure rate is huge as that makes the use of high pressure/high flow rate/high current a must.
Also getting the moving parts to cut in the same spot is easy, if it wasn't for the THC that keeps moving that spot .....
It is doable, i do not care about the complications, i will build two of them, i hope they fail, i still would not care, they will work perfectly for round tube!

tommylight wrote: Also getting the moving parts to cut in the same spot is easy, if it wasn't for the THC that keeps moving that spot .....

It may not just be the THC, the anode spot where the arc terminates to the material oscillates up and down from the top surface to the bottom surface causing those striations you see in a cut. I suspect you would need to be able to control arc current to cut cleanly.

I do remember Grotius showing us one he built.

Round tube.

for round tube I just use one of these with a bracket to hang it underneath / supported to my table + allow me to square it.

i.ebayimg.com/images/g/AwgAAOSwUY9dPzvk/s-l1600.jpg

with a bit of an uprated stepper motor (nema 23, 4.2A, 3.1Nm)
www.cnc4you.co.uk/Stepper-Motor/Nema23-3...Nm-60BYGH301B-Nema23

I don't do a lot of tube, but it works fine for my hobbist needs (beats an angle grinder + flapdisc / file....)