12 Replies Latest reply on Sep 1, 2016 7:36 AM by Gianluca Mattaroccia

    Tangent Mates

    Steve Crompton

      Does anyone else have tangent mates that one day just decide to flip to the other side? It drives me insane when it happens. Is there any plans to get this sorted out Solidworks? For now I have to spend extra time putting reference planes in and using coincident mates on them.

       

      Its bad enough when it happens on a model I'm working on, but I've also had it in the past when the factory has opened a drawing via e drawings for manufacturing and the mates have flipped. Thankfully the issue has always been caught before wasted production happens.

       

      Thanks

       

      Steve

        • Re: Tangent Mates
          John Stoltzfus

          What year release are you using - I know the older releases had that issue - it is best to add a point to the quadrant of the circles (in the sketch) and mate those points...

          • Re: Tangent Mates
            Glenn Schroeder

            I've pretty much quit using tangent mates too.  I usually use distance mates instead.

            • Re: Tangent Mates
              Mike Pogue

              Tangent mates are nonlinear, so they require iteration to solve. It is that nature of most (all?) iteration schemes that they find the nearest solution, rather than the one you meant. Iteration is also very, very slow when compared to linear solution. This is mostly a limitation of mathematics, rather than a limitation of SolidWorks. Fixing this would require adding business logic to the mathematical solution, which would slow everything down and add a new potential source of instability.

               

              Since tangent mates are a) slow and b) unstable, I avoid them if possible.

              • Re: Tangent Mates
                Christian Chu

                It happened to me on some models too

                Here is a trick I used (not always work) - add extra angle or parallel mate

                • Re: Tangent Mates
                  David Sloop

                  I'm designing a conveyor system right now, and am reminded of why I quit using tangent mates 15 years ago.

                  They fail way too readily.

                  Trying to use one conveyor roller level to constrain the next, and have planes set tangent to the last rollers on each section.

                  Has been an epic failure. They keep flipping whenever I change one of the heights, hoping the others would update along with it.

                  I don't know why, but they always end up failing..

                  I try and avoid using them as much as possible.

                  I am looking at ways to re-constrain my model to remove the tangent mates now.

                    • Re: Tangent Mates
                      John Stoltzfus

                      David Sloop - If your rollers are all on the same plane (Z) then you could try to do what I've done in the past  -  In the main circle sketch add a square construction line sketch that is tangent with the circle then you could mate the vertex or any of the straight lines coincident...

                      • Re: Tangent Mates
                        Mike Pogue

                        I don't know if I understand your issue perfectly. But if you want to constrain the position of cylinders, you very definitely want to do it with the circle origin or with the axis of the cylinder, and not with a tangent mate. As to why they keep flipping, see above. There are two solutions to the equation that defines a tangent mate. SW has no idea or interest in which one you want.

                        • Re: Tangent Mates
                          Paul Risley

                          David,

                           

                          From my conveyor design days one tool I found benefecial, and it may prove of no value for what you are doing. Is using the view temporary axis button. This way you can pop the center of a roller on existing geometry planes without too much hassle. I know in 3D world there are a million ways to skin the cat, but I found this useful especially in stepped conveyors or incline tangent plane ones.

                          Hope it helps.

                          • Re: Tangent Mates
                            Gianluca Mattaroccia

                            Hi David,

                            been involved with conveyor design for some time in the recent past and I still do some work in the packaging industry.

                            I am very familiar with what you are saying. I get to work around the problem by creating a plate, tangent to the roller, in the part or sub-assy. In the main assy I then mate coincident planes. Of course there are cases where you need to mate the chordal action of a package in a curved section where the mating is a little more tricky but I use the same criteria and never have a problem.

                            The tangent mate is tricky also in simple sketch mode, you have to make sure all the entities interested by this relation are properly set.

                            Good luck