7 Replies Latest reply on Feb 6, 2008 6:28 PM by Jerry Steiger

    Tangent Face Constraint

      One important feature of 3D sketch splines that I did not have time to cover in my Curves presentation at SolidWorks World this year was the tangent face constraint.

      The reason that this is so important is that it does not often need a reference projected curve or intersection curve to be used as a "bridge curve." The problem is that it is rather undiscoverable in that you must pick both the spline, the edge it lies on as well as the surface to be tangent to. To see click on the following link. We are working on ways to make it more discoverable.

      click here a face tangent constraint.avi

      To play this video you might have to download the Techsmith codec from: http://www.techsmith.com/download/codecs.asp

        • Tangent Face Constraint
          Kevin Quigley
          Thanks Mark! Didn't know that. Will SolidWorks be posting up the SWW presentations to the customer portal?
          • Tangent Face Constraint
            Charles Culp
            Mark, I have done tangencies to faces before (2007), but it was always awkward controlling the direction it came out. Will it always be perpendicular to the edge selected now? Or is there some other method for controlling the direction of the tangency?
              • Tangent Face Constraint
                Charles, for this particular type of constraint - no, there is no flip tangency. Frankly with a bridge curve (2 point spline) like this it is near impossible to do, and I've never seen it.

                Now on are regular spline tangency constraint to an edge or another sketch element, yes, I have seen it flip the wrong way. In cases like this - Yes, there is a way. click on the spline and over in the PM RMB over the Tangent relation. On the RMB drop down mini menu you will see three choices. "Delete", "Delete All" and "Flip Rotation".
                  • Tangent Face Constraint
                    Charles Culp
                    Thank you for the response Mark, but I was unclear in my question. I have attached a screenshot and a model to hopefully make it more clear.

                    The way tangencies work with faces has obviously changed in 2007>2008, so I was hoping to get some insight, even though I hadn't worked with them yet. I spent some time with it, and somewhat answered my own question. The other half of my question is still unanswered, and seems to have brought up an inconsistency in the sketching constraints.

                    My technique (learned for 2007) to control tangencies of splines to faces was to draw a construction line on the face, coincedent with the edge, and make either the construction line tangent, or the spline tangent to the face, and then make the two lines tangent to each other. I could then constrain the construction line angle as required. This way I could control the direction of the spline "on the face".

                    My point is when you make something "tangent to face" you are only defining two degrees of movement, there is still the 3rd degree that needs to be constrained.

                    So after using the tool in 2008, it does seem to work more fluidly, there were some times in 2007 where my technique would tell me that it was overconstrained, even though it really wasn't. Now, however, I have noted on the attached file that I can adjust the spline by moving the construction line, and it will make the spline non-tangent to the face. This, however, will fix itself upon rebuild after closing the sketch.

                    So am I using a valid technique for controlling the direction of the spline, or is there a better way of doing that?
                      • Tangent Face Constraint

                        The reason that these update after you leave the sketch is the difference you are seeing between two different Constraint solvers that we use; one for our 2D sketch and another for our 3D sketch and therefore it doesn't solve until you rebuild the sketch feature. This is because we're (SW) are doing some of this solving on our own verses the solver component.

                        Construction geometry is nice for defining the direction like you're doing but it is somewhat subceptable to changes that might be made in the existing surface when parent features change (Boundary surf you've defined.)

                        What I do if I want to drive direction of the spline, is to project a curve on to the surface with a simple sketch. Be sure to see the workaround to the bug when doing this that I posted in this same forum (hopefully we'll get this fixed soon.)

                      • Tangent Face Constraint
                        Jerry Steiger

                        Thank you so much for pointing out that we can flip the direction of the tangent relation. Heaven only knows how much time I have wasted trying to fix this problem. Now I've just got to remember how to fix it the next time it happens!
                    • Tangent Face Constraint
                      Charles Culp
                      I saw that post as well, thank you for the insight.