Yes SAC is a great program. However, I make a flowchart and I need a for cycle to run the flowchart depending on a condition repeatedly. Unfortunatelly SAC is not give any cycle (For, do while,etc). Also tunnel sections includes big circular arches. SAC produce curves with maximum 100 chords. And intersection point of a point and a circle, catches one of these chords. When I use this intersection points to draw another circle with same center point, circle doesnt occure because of this reason. Because intersection point is not on the circle, it is on the circle's chords. I spent too much time to get enough presicion by splitting arches with many helper points. As a result I wonder preparing subassemlies without SAC.