Hello All:
This is an intriguing problem. I believe it may lend itself to a simpler solution, but not as visual as a CAM program. If you slice a tube at a given angle, the line at the tube surface is a path in X, (the long axis of the tube) and angle A, the corresponding point as the tube rotates. This is assuming that the tool/spindle centerline, or the plasma torch remains over the tube centerline, Y, as the tube rotates. Therefore, a series of point pairs, X,A will drive the machine along this path. Furthermore, each 90 degrees of rotation is a mirror image of the previous 90 degrees. This path can be calculated in Excell. I can expound on this further, if interested.
Regards,
John