8 Replies Latest reply on Jul 31, 2014 2:19 PM by Jamil Snead

    Fitting Linear Patterns within a curve

    Shrinath Balakrishnan

      Hi guys,

      I am trying to design an aircraft rib with a diamond like pattern between 20% chord and Trailing edge(TE). I started with the sketch of one diamond and used linear sketch pattern to continue upto the TE. However I would like the linear patterns to fit along the shape of the aerofoil.For better understanding,  I have uploaded the solidworks file where this is shown and also a handdrawn sketch(rough) of how the final pattern fits onto the aerofoil shape. Could any of you please advise me on the easiest way to achieve this.
      My only other alternative right now is to manually draw each diamond to fit to the aerofoil, and this is just impossible since there are about 50 of those.

       

      I am using the Solidworks Education Edition 2013

       

      Thanks in advance

      Shrinath

        • Re: Fitting Linear Patterns within a curve
          Jamil Snead

          I've played around with several different ideas and I can't get anything to work. You might have to just draw them all manually.

          • Re: Fitting Linear Patterns within a curve
            Greg Miller

            You can sketch a curve and then put points on the curve where you want the triangles to go, then pattern the "triangle" cut feature to the points.  It will take a couple of features (the "cut" then the "pattern") to do this.  I'm not sure off the top of my head if you can do the same thing with just a sketch.

              • Re: Fitting Linear Patterns within a curve
                Jamil Snead

                But the shape of the triangles is changing as they move along the curve, because the width is constant and the height is changing. That's what makes it difficult I think. At least that's what I interpret from the original sketch and idea of using a pattern. Shrinath is that what you wanted, or do you want the angle of the triangles to stay the same and have the spacing adjusted accordingly?

                  • Re: Fitting Linear Patterns within a curve
                    Shrinath Balakrishnan

                    Yes, that is right Jamil. So, the width of the triangles always remains constant. The height needs to be adjusted accordingly to coincide with the curve. As far as I checked none of the patterns allow for a change in shape from the original pattern.

                     

                    PS: Have started doing the manual way, but would be nice to know if any solutions for this exist, since I would need to do more like this in the future.

                     

                    Thanks guys

                      • Re: Fitting Linear Patterns within a curve
                        Jamil Snead

                        Here's a method I came up with that might save a little bit of time. In general if the curve is symmetrical it may be quicker to do the top half only first and then mirror everything.

                         

                        First make a sketch of one triangle with a centerline up the middle and the horizontal construction line across the bottom of the triangle. Don't worry about the top of the triangle coinciding with the curve yet.

                         

                        pattern1.PNG

                         

                        Then linear pattern the top edges of the triangle (not the inside edges or the centerlines). Don't dimension X spacing, instead make the sides of the triangle coincident as needed. From here on out some lines will be black even though they aren't fully constrained. Don't worry about that.

                         

                        pattern2.PNG

                         

                        Then do another linear pattern of the centerlines. Again, don't dimension the spacing but instead make the first of the patterned vertical lines coincident to the top point of the triangle.

                         

                        pattern3.PNG

                         

                        Now delete that coincident mate and dimension the spacing between centerlines where they sit. This seems weird now but there is a reason for it.

                         

                        pattern4.PNG

                         

                        Then delete the pattern relation for the triangle lines. Now be sure not to move any lines yet.

                         

                        Now do Tools > Dimensions > Fully Define Sketch. Uncheck the Dimensions box and check the Relations box, so it will only add relations, and deselect every relation except coincident. This will make the tips of all the triangles coincident with the centerlines that they sit on. It will also make the bottoms of the triangles coincident with the horizontal construction lines.

                         

                        pattern5.PNG

                         

                        The next step is to set the top of each triangle coincident to the curve.

                        Then mirror everything.

                        Then offset all of the lines to get the inside of the diamonds.

                         

                        SolidWorks started running slow for me after the auto-relation thing. I think it's because there were so many of the horizontal construction lines and each of those got coincident with each of the triangle endpoints. I think it would be better to do two small vertical construction lines that meet up with the outside of the first triangle instead of the one horizontal one.

                         

                        Anyway that may save you time or it might be too complicated. But that's the best I got!

                          • Re: Fitting Linear Patterns within a curve
                            Shrinath Balakrishnan

                            Wow, yes, does seem complicated, but will try it out neverthless.

                            Thanks for the help !

                              • Re: Fitting Linear Patterns within a curve
                                Jamil Snead

                                I went through the steps and tried again and I have revised the method a little bit. At the end of the steps before I said it might be better to use a couple small vertical construction lines instead of the one horizontal one at the base of the triangle. Now I think even just a point placed at the bottom end of each outer leg might be good enough. Also after you pattern the centerline and the points, I think it is better to delete the triangle pattern relation, then do the Fully Define Sketch, then dimension between vertical centerlines. Dimensioning the centerlines before doing the Fully Define Sketch can make it fail to add the coincident relations at the tops of the peaks because of rounding error I think.

                                 

                                Also at certain points the sketch might get overdefined so you can just delete some relations until it is good again (for me deleting the equal length relation of the first triangle's legs helped).

                      • Re: Fitting Linear Patterns within a curve
                        Jamil Snead

                        I don't know if you still need a solution for this, but I just realized there's a really easy solution using the "Vary sketch" option for a pattern.

                         

                        Start by drawing one diamond, and constrain it with a horizontal position dimension and make the top and bottom coincident to the curves.

                         

                        varysketch1.PNG

                         

                        Then extrude it. Next start a linear pattern, and for the direction pick the horizontal position dimension. Set the spacing you want and number of instances, and in the Options area check the box for "Vary sketch". This will update each instance to keep the sketch constraints of the original sketch.

                         

                        varysketch2.PNG

                         

                        It's as easy as that!

                         

                        varysketch3.PNG