17 Replies Latest reply on Dec 16, 2014 9:55 AM by Nenad Simonovski

    Need some pointers on sketching a log. spiral in SW2008

    Troels Bertelsen

      Hi all


      I'm a 22 year old student who uses some spare time getting acquainted with using solidworks to tackle the design of speakers for later optimization. Please do note that i'm not very skilled so you may have to elaborate on your answers.


      Well, the task at hand is to model a speaker with an interesting design, namely the B&W Nautilus as seen here:




      What i'm trying to sketch is the bottom part which resembles the shape of a logarithmic spiral. I've then made a function in excel and extracted a couple hundred points to describe the curve and used the spline function to get a baseline. Now, to make a surface of the speaker enclosure, i want to draw a skeleton like seen here:




      I've tried some of my ideas to do it, but haven't suceeded. I've tried using the curve as a guidecurve and made two  circles sketches as a profile for the loft-feature and a few others. It seems very very time consuming to do a sketch like the one above by defining points and creating planes for each, onto which to draw a circle and finaly use a surface feature to connect them. This is what i have in my initial design phase:




      Any help will be greatly appreciated.


      Best regards, from Denmark, Europe



      PS: Can i use the final model to make a cut-extrude to make a primitive mould?

        • Re: Need some pointers on sketching a log. spiral in SW2008
          Charles Culp



          I have attached how I would create a Nautilus. I did not plot the path very well as you did, so I could not finish it. If the path were to be mathematically correct, it should finish just fine.


          You will want to use the least number of ribs possible. You can see I only used one per revolution, that would be best. The tool you need is centerline loft. Use each rib as a loft profile, and then the spiral path you generated as the path. Make sure to add a "curvature to face" end condition at each transition to get a very smooth transition. Good luck!


          And yes, you can make a mold with solidworks. There is an entire toolbar dedicated to making molds. Create a parting line with the parting line tool. Then create the mold shape (turn of "merge entities" if it is inside the part file, or do it in an assembly as a seperate part), then use the mold split tool. There is a very nice tutorial in the SolidWorks Tutorials about how to do this, and is a good quick lesson.

          • Re: Need some pointers on sketching a log. spiral in SW2008
            David Paulson



            I have experienced similar issues when trying to create volutes for centrifugal pumps.  Loft features in SW can take on a life of their own.  Charles Culp created a rough approximation of your B&W speaker, but I don't think that with a lot more work he could ever make it look like the B&W speaker.  For some reason the curve generation is not smooth.  I was lucky with a pump volute because it did not need to spiral down to "nothing" like a naulitus.


            While I would start with the same spiral guide curve that you are using, I would break my nautilus into maybe 50 distinct lofts (based upon the number of ribs on your model) so that I can adjust the diameter of the nautilus as needed.  I could also then add the rib features between each loft without too much difficulty.  This may sound like a lot of work, but it does give you control at each step and enables you to get to the finish line with the result that looks like B&W's nautilus speaker.  Trying to accomplish this with one step would be incredibly difficult in SW.


            I will add to my post as follows:  The actual model is a tapered tube that is just rolled up to form the nautilus.  In reality the tube cannot overlap itself.  But in SW I do not believe that you can specify this parameter.  There would need to be a command like wrap tight, or wrap to a 6mm gap to allow for the ribs.  I am still on SW2009 so I do not know if this capability may exist in SW 2010........but if not it would be a great enhancement request.

              • Re: Need some pointers on sketching a log. spiral in SW2008
                Troels Bertelsen

                Hi David


                Yeah, i've just tried to do it but it seems the loft feature needs a lot of small sections to provide a decent output.


                The reason why i'm doing this is because i want to measure the internal volume (Which is an important parameter when choosing a speaker driver) and possibly export to Ansys 12.1 to investigate both mechanical loads and the flow inside via CFD analysis, which is the main topic of my semester. I'm just doing this as a side project to hone my skills because i find it a valuable skill to have as an engineer, even though we don't have any lectures in CAD-modelling.


                One way of achieving what i want could possibly be doing the following and lay out points for every 5 degrees, which to use for making a plane on the curve, and then continuing onwards making the ribs. Then possibly use a suitable surfaceing feature to connect the ribs to form a solid body.



              • Re: Need some pointers on sketching a log. spiral in SW2008

                Hi! You can download log.spiral generator from this forum:


                1. http://fsapr2000.ru/index.php?showtopic=34593&view=findpost&p=316502 , post #18 - this is mathcad document. Document creates txt-file with coordinates of 3d-points.SolidWorks reads them and creates a curve; (#23 has videofile with instruction)
                2 http://fsapr2000.ru/index.php?showtopic=34593&view=findpost&p=316627 , post #44 – macros for log.spiral generation



                • Re: Need some pointers on sketching a log. spiral in SW2008

                  It is rough example. Examine this.logspiral.JPG

                    • Re: Need some pointers on sketching a log. spiral in SW2008

                      Modeling with sweep:

                      1. Create curve.

                      2. Create  sketch for plane.

                      sketch for plane.JPG




                      3. Create sketch for path.

                      Sketch for path.JPG

                      4. Create sketch for guide.

                      Sketch for guide.JPG

                      5. Create sketch for profile. Insert two points.

                      Set Coincident relations with circle and points.

                      Set PiercePoint relations with first point and path.

                      Set PiercePoint relations with second point and path.

                      Set Vertical relation with circle center and any point

                      sketch for profile.JPG

                      Circle may change radius.

                      6. Create Surface-Sweep or Sweep-Boss/Base

                      sweep creation.JPG

                      7. Result


                    • Re: Need some pointers on sketching a log. spiral in SW2008
                      Troels Bertelsen

                      Hi Guys


                      Thank you all for your help. I really wish i could award points to more than one answer because not only one person deserves it.


                      Thank you again - i will return if i have any more difficulties in SW2010 - thats right, my school just upgraded to SW2010 (Even though 2011 is soon released..)


                      Again, thank you all!