I used the Inventor Design Assistant to create a simple internal cylindrical cam ring groove that I want to mill on the ID of a tube using a 4 axis CNC mill. I plan on laying the 4th axis rotary fixture on the mill table with the rotary axis facing up. I will use a 90 degree head on the spindle to hold the ball end mill in order to reach into the ID of the tube - whose axis is obviously also facing up. I am having a hard time generating the tool path and gcode - confusion on material setup and tool orientations. Any help would be greatly appreciated! Thank you.