6 Replies Latest reply on Jun 1, 2018 11:16 AM by Chadli Mascarenhas

    Driving the side of a curve

    Chadli Mascarenhas
    Chadli Mascarenhas Mar 27, 2018 3:26 PM

      Hi,

       

      I'm looking to create an equations driven sketch feature that will sometimes show up on one side or another of an axis/plane. The problem is that I can't find a way to explicitly make my arc stay on "the right side". I am attaching a simple part file with a sketch that exemplifies this. If I have a rectangular-like shape with an arc for one of the sides, then if D2 is toggled between something greater and smaller than D1 (flipping the sides) , then the direction of the arc is automatically flipped to the outside. How can I make the arc stay along the same edge of the "rectangle"?

       

      Similar (same?) question: is there a way to toggle from the set of possible solutions to a series of dimensioned sketch features without triggering the overdefined/unsolvable function?

       

       

      Thank you in advance

        • Re: Driving the side of a curve
          Dan Pihlaja
          Dan Pihlaja Mar 27, 2018 4:03 PM (in response to Chadli Mascarenhas)

          Took me a bit to figure out what you were talking about.   What you want to do is prevent the flipping of the arc when the right side line of a rectangle is dragged past the left side line of a rectangle (assuming that the bottom "face" is the arc itself).  Inside 1 sketch, I am not sure that you could get away with this, as the direction of the arc is flipped to its compliment.

           

          The only way that I can get it to (sort of) work is to make the arc side in a totally separate feature (like cutting a rectangle to make it.   In order to get it to work, NONE of the geometry from the cut side can be attached (constrained/dimensioned) to the geometry of the rectangle.   ALL of the geometry would have to be constrained/dimensioned from the origin and planes (or reference geometry).  This is because the direction of all lines involves "flips" as soon as the "right" side of the rectangle passes over the "left" side of the rectangle.  If this is something that you would want to be controlled via global variables/configurations, you could link both the rectangle solid and circular cut to the same values in your equation manager/design table.

          • Re: Driving the side of a curve
            Rob Edwards
            Rob Edwards Mar 27, 2018 4:16 PM (in response to Chadli Mascarenhas)

            Hi Chadli

            unfortunately Im stuck on 2016

            Could you post a screenshot of your sketch?

            • Re: Driving the side of a curve
              Chadli Mascarenhas
              Chadli Mascarenhas Mar 30, 2018 5:04 PM (in response to Chadli Mascarenhas)

              Thank you so much guys. I had to redirect my efforts a bit, but so far a mirror with an offset seems to get around the curve flipping. I will post a picture and potentially a model of the solution once I get it down.

              • Re: Driving the side of a curve
                Chadli Mascarenhas
                Chadli Mascarenhas Jun 1, 2018 11:16 AM (in response to Chadli Mascarenhas)

                Here is what I came up with. This solves a slightly different question than I originally asked, but it does what I need.

                 

                The idea of a reference line a certain distance away from the actual object came from someone else's post. I'd link it, but I recently lost my bookmarks and can't find it right now.

                 

                Radius <= Diameter still gets into a tricky, and apparently irreversible situation where the arcs start to flip again. So it would still need some modifications to get to full hemispheres (same oversized diameter but with sag/offset compensation), but this works for what I was looking for and seems stable enough. The sine is just for simplicity in case there are several versions of this sketch in the final object, and for "fun". The final version is/would be equation driven for the diameter, radius, vex2cav, and d4, etc.

                 

                 

                 

                Then it just needs to be turned into some sort of revolved feature. It might be too complex of a solution. Maybe the hole wizard be used for this type of thing...