12-13-2012, 10:24 AM

NORMAL defines the direction vector that points in the direction perpendicular to the plane of the circle. For example, if you point the nomal vector in the Z direction and you do a CIRCLE move in the X-Y plane you get a true circle. Now, if you point the direction vector in a direction that is an angle to the X-Y plane and then do a CIRCLE move in the X-Y plane, PMAC computes the CIRCLE in X-Y-Z space, but only makes the move in the X-Y plane, hence you get an ellipse. Think of it like the X-Y plane is cutting a cylinder whose axis is parallel to the NORMAL vector. If you play with this a bit you will understand how to do the algebra to get what you want.