See my setup
http://www.scanalex.com/CNC.html as the table rotates from a smaller diameter to a larger one, you
need to allow for the end mill diameter. Because a screw machine cam is all based from the center point of the cam, the rotational of the degrees needs to make up the diff when the end mill clears the top of the rise and needs to start milling a large radius. If you don't, then the end mill will cut off the top of the start rise and at the bottom of a rise or drop the end mill
will not truly be in the right position.
Picture the X moving the end mill out to make a bigger diameter as the A rotates. If the rise on the screw machine needs to
be 30° then if you rotate the table 30° and move the x out to the next diameter, the end mill will be leaving too much at the bottom of the rise and may be ok at the top.
Then you need to do the flat or dwell on the cam. If its 5° of dwell or flat diameter, and the A axis rotates it only 5°, the next move to a smaller diameter would cut off part of the top dwell. You would only end up with 3-4° of flat or dwell.
See what I mean? I hope. lol