5 Replies Latest reply on Jan 29, 2008 12:55 PM by Mark Matthews

    Creating stable sketches

    Carrie Ives
      I have years of experience with Pro/E and am slowly learning Solidworks (2007). One of the things that is frustrating me, when I create a sketch, it forces me to create my dimensions to edges rather than to the faces. In Pro/E, I was taught that dimensions (and other relations) should be created to faces rather than edges because edges aren't as stable. Is there a way to get Solidworks to let me create my dimensions to faces rather than edges? I just feel that I am having too many sketches fail later down the road because of this. Are there general rules for creating stable sketches?

      Thanks,
      Carrie
        • Creating stable sketches
          Charles Culp
          You can indirectly dimension to a face, but if you want it to be more stable I suggest always dimensioning to other sketches. Use the "convert entity" tool to bring those other sketches into your current sketch, and then convert them to construction lines.

          Sometimes this is unavoidable. Then you can "convert entities" on either the edge or just dimention to the edge, like you were doing. You could also possibly use the "intersection curve" tool to create a line where the face intersects the sketch, thus dimensioning to a face. I don't think saying that "faces are more stable" is a very accurate statement though.

          They are both unstable enough that I always dimension to other sketches whenever possible.
            • Creating stable sketches
              Dan Riffell
              Charles is leading you down the right path. I try to use as much other geometry as I can in my sketches. Learn to love the Convert Entities tool.

              My process is pretty straight-forward. I create the basic sketch by either drawing new geometry, reusing geometry, or both. Then I apply as many relations to the sketch entities as possible while adhering to the design intent. Only then do I ever dimension anything. In my experience, the fewer dimensions you can use to capture your intent the better. This should get you on the road to stability in no time.
            • Creating stable sketches
              If you wan't to use faces for dimensions/relations then instead of sketch you have to use 3d sketch. I use it rarely so not sure of the drawbacks if any it may have.
              • Creating stable sketches
                Roland Schwarz
                Add me to the "I feel your pain" list. When SW gets around to meaningful enhancements, this should be one.
                • Creating stable sketches
                  Mark Matthews
                  I share your frustration. Any planar face should be considered a datum. Faces are always going to be more stable in a model than edges. Since you can dimension to datum planes you could always create a datum through the face and dimension to it, but for practical reasons I do what Charles suggests and always try to diemsion to the original sketch entity that created the face in the first place. The sketches are always accessible, unlike the internal sketches in Pro-E. Since the face is identified by the sketch entity that created it, your new dimension or constraint will be stable as long as the original sketch enitity exists; even if you delete the feature that created the face (sketches don't get deleted with the feature unless you specifically check the absorbed features toggle).