I'm not defending the way that SolidWorks handles splines, but I think that there is probably an historical reason why the Intersection Curve is in the Sketch Tools menu. I think that when it was first developed, it only allowed for the intersection of a body with a plane and that plane was, of course, the sketch plane. When the tool became more capable, it would have made more sense to put it in both the Sketch Tools menu and the Curves menu, but someone dropped the ball on that.
I've never had this problem with intersection curves. As long as the surfaces intersect, the curves update accordingly.
Perhaps the modified surfaces no longer intersect?
The 2 surfaces are always intersecting.
Just that the intersection isn't updated.
To Jerry Steiger : OK, SW surely evolved, but as soon as the intersection of 2 surfaces beacame a curve, this choice of construction might be suggested in the curve menu.
A similar case with a CTRL C on a surface : as soon as an Offset Surface command with zero offset did a CTRL C effect, instead of saying that this feature is impossible, when a surface in the clipboard, a CTRL C could have a CTRL C effect, as soon as a surface was in the clipboard !!!
Or when I can't flip a sketch, because the sketch has exterior relations, something very useful and userfriendly would be to have the list of exterior relations making obstruction !!!
And to come back with intersection of 2 surfaces, it's really boring that the list of the involved surfaces becomes "an intersection of 2 faces0" !!!!
To adjust a curve, picking among an heap of surfaces would be useful, but with the present version, you have to redefine the entire construction.
I'm not defending the user interface either, just suggesting why it ended up the way it is; just another mistake by SolidWorks. I do have to admit that a couple of times when I have suggested changes to the interface that seemed very simple to me, the guys at SolidWorks pointed out some things that made it not nearly so easy and not really worth doing.
You can click the right mouse button in empty space and choose Display/Delete Relations and then choose External in the box below Relations. You can choose to Delete All. It's not automatically presented to you, but at least it isn't too far to go. Unfortunately, it is sometimes a royal pain to have to delete all of the relations and then add them all back in again. It doesn't seem like it would be impossible to suspend the relations, flip the sketch elements without relations, and then add the relations back in, but I suspect it is harder than I think.
It is very scary to me that intersection curves could get out of sync with the underlying surfaces.
Yeah, I was about to say, sometimes Solidworks is not so good at perserving intersecting sketch relations but as far as a basic two surface interesection curve, it seems to work just fine.
What program did you come from where you were using a curve entitiy instead of a sketch entity? Is it Pro-E or Inventor? Because the 3D Sketcher's in those programs are very limited wheras most of Solidworks curve tools are in the 3D sketcher.
Based on your expressions and tone, I'd say that you recently switched to Solidworks-maybe against your will-and you're trying to rely on your previous experience (maybe with Rhino or Max?) to tell you how to approach modelling. If that's the case, I encourage you to take some offline time away from whatever project you're working on and read up on how the surfacing tools in SW are intended to operate.
I have seen the problem of intersection curve not updating when the surfaces were changed. My changes were small. I think that I just fixed the result and hoped that it does not bite me down the line.