In BikeCAD, we set the angle of the handlebars with respect to the horizontal. As the angle is adjusted, we can also play with the position of the brake levers. If at some point down the road, we change the head angle (exaggerated here for demonstration purposes), our handlebars will remain at the prescribed angle with respect to the horizontal. However, in the case of a one piece bar and stem, this is not a realistic scenario. As our head angle changes, the angle on a one piece bar and stem must change as well. This is why, in BikeCAD version 15.0 we have a checkbox for One piece bar and stems. When we check this box, the angle of the handlebars is set according to ∠2 which is the angle of the handlebars with respect to the head angle. As we make changes to our head angle, the one piece bar and stem will move as a unit.
As always, we can save handlebars and stems as standard parts. However, because handlebars and stems each have their own menus for standard parts, standard one piece bar and stems will still have to be saved as two separate parts.