5 Replies Latest reply on Jul 4, 2013 4:03 AM by Igor Rybalka

    Loft profile with hole

    Igor Rybalka

      Hello everyone,

      I'm sorry if this was already answered, I didn't find such topic on forum.

      My problem is that I want to make a loft for a profile that have a hole.

      I cannot use loft cut after a loft because I do not have a guide curves for inner hole profile. I do not even know what shape this hole actually should become after a loft.

      My two guide curves are complicated and they are adjacent only to  outer profiles and if I try to use them for inner hole profile - SW goes crazy and twists inner cut loft in a very strange way. My guess that this is because they are too far away and actually not applicable for it. What should I do?

       

      loft.png

       

      Thank you for any suggestions.

      Igor.

        • Re: Loft profile with hole
          Anna Wood

          Post your part with what you have tried.  Use the Advanced Editor link in the upper right of the dialog box.

           

          Cheers,

           

          Anna

            • Re: Loft profile with hole
              Igor Rybalka

              Hello Anna,

              Please see part attached. What I am basically trying to achieve - is to have a inner loft cut that will follow the shape of the outer loft base.

               

              Thank you.

              Igor.

                • Re: Loft profile with hole
                  Kieran Choy

                  I'm not sure if this is possible with the geometry you've supplied. The reason you can't loft the two circles together with the existing guide curves is because guide curves must pierce (touch) the sections. Centerlines (like sweep paths) do not have constraint, but you can only use one curve at a time.

                   

                  I've attached my attempt, which is a potential start.

                   

                  The Surface loft is used to create an edge, which can then be selected as a centerline (or guide curve) for the Loft cut.

                   

                  The problem, as you can see, is that because the two profiles are circles, the cross section remains circular throughout the loft, and end up cutting through the original body. This is because the original body has two elliptical ends but does not have an elliptical cross section throughout. So you would need to try and work out what shape the circles would become as the outside profiles are deformed, which as far as I know is impossible to do in SW.

                   

                  If this was a sweep and your geometry was slightly different this would be much more easy to solve - is this possible?

                    • Re: Loft profile with hole
                      Kieran Choy

                      I lied. Here's an attempt with a deformed hole. It's possible, but not necessarily pretty or "correct". If you understand the general method below you can try tweaking how the guide curves are made to maybe get a better result.

                       

                      Basically I'm using lofted surfaces as a way to create edges that are curves that are the "average" between two existing curves. So the ruled surfaces allow me to create an intersection curve along the outside edge of the part, and then we can use our loft surface to create an edge that theoretically is the ratio between the circle center and circle edge, to the circle edge and the outside of the part.

                       

                      Hope this makes sense. I still if it's possible a sweep would be a better option.

                        • Re: Loft profile with hole
                          Igor Rybalka

                          Hello Kieran,

                          Unfortunately I cannot use sweep as the real part is a wing and airfoil does change its shape along the way. Nor hole is a simple circle - it's a bit more complicated. But I've got the main idea - use lofted surfaces to approximate curves for some "key" points that can be used later as reference when lofting a hole.

                          You are right that I have know what shape the hole would become to make the loft "correct", but approximation based on distance to the edges is good enough in my case.

                          Thank you!