Plasma CNC Pipe Cutting Machine

 
Hey everyone,

I am retrofitting a CNC Plasma Pipe Cutting with 6-axis. XYZABC. I am wondering what Kinematics module to use. I have encountered two types of pipe cutting machines.

1. The pipe is placed in a chuck and rotates the a-axis
2. Plasma torch head navigates around the pipe.

These to me are totally different calculations and I would assume would be handled by the CAM software? Would i just use genhexkins and the rest is just mapping each axis and joint?

What I am trying to understand is who is in control of the machine path, the CAM software or the linuxcnc kins module. 
I want to cut a line in the pipe at point x1=0 a1= 300deg to x2=100 a2=300deg, who calculates that trajectory?
 

If you want to draw a line on a pipe, it does not matter if you rotate the pipe or rotate the pen.

Here is your homework. I've already done this. Google coping calculator and review the maths and graphics for a notch in a pipe to be butt joined to another tube. print it on light card and cut the outline out. Wrap it around your tube, trace it with a felt pen and cut that notch out with an angle grinder. 90 deg join is easy to cut. 45 deg is a bit harder (as its deeper) with the angle grinder but it can be done fairly easilly. The maths creates the desired outline and won't care how you cut it! Options 1 & 2 are identical.

If you are cutting a length of RHS, it still has a standard profile defined in an engineering standard so you can still follow the surface to cut it with similar maths.

I think Its predominately a CAM problem but when you want to angle the torch, some kinematics might help. Not sure if it will help but 2.10 now includes some tangential headings which may assist. I think the full 6 axes may let you cut I beams

Thanks for that @rodw. your contributions in this forum is a godsend. I am still a newbie, nonetheless plan on contributing as much as i can.

The geometry makes sense, i didn't struggle with that. i always unfolded the pipe in my head. the geometry of the pipe is the same but i guess the g-code produced by the CAM is different.

In option 1, where the pipe is on a chuck its a mere single axis rotation command of -60 degrees, and then a movement along the x-joint for notch.

In option 2, the torch would have to maneuver along the pipe which is both a y-axis, z-axis movement, and also c-axis rotation, then a movement along the x-axis for a notch.

Writing all of this has made me realize it is CAM dependent as you said. so nothing would change but I would need to use the genhexkins for full 6-axis. I'll have a go at it then.

Note that 'genhexkins' is meant for hexapods, which may or may not be what you are using.
linuxcnc.org/docs/html/man/man9/kins.9.h...Hexapod%20Kinematics
 

I am not. I just read trivkins and it also supports xyzabc. so ill have a go at that.