I know this may sound silly, but on a conventional mill, we refer to the spindle moving in X+, the spindle is not actually moving anywhere, but the table is feeding left. When the spindle is feeding in Y+, the spindle is not moving towards the machine column, but the table is moving away from the column.
So you see, it is a "frame of reference" problem. The best way to keep it all straight, is this: if the tool is cutting a path through the part, towards the right side of the part, that is an X+ movement.
That direction defines the universal "zero degree" direction, or start point. The left end of this line could be called X0Y0. Then starting from the right end of this cut line line and rotating around the left end point, counterclockwise, 90 degrees,(looking down on the table), you come to the Y+ axis. Any cut where the tool progresses towards that edge of the part is a Y+ movement.
Confused?
