3 Replies Latest reply on Aug 22, 2011 8:24 AM by John Withers

    Archtop Guitar..Still can't get it right....driving me nuts!

    John Withers

      Hi All,

       

      I posted something similar in the part forum, but I think the surfacing forum is more appropriate...still struggling with this, I thought I had it!

       

      Anyway, I have attached by curves file, to give you all an idea of what I am trying to do...this is one of the hardest things I have had to model , and I am not sure where the H___ I am going wrong, as SW refuses to co-operate with me, and it is fighting me all the way! (sw2011 x64 SP4)

       

      I am sure I am doing something really stupid, but for the life of me, I am not able to figure it out...anyway, as you can see from my curve model, I am simply trying to "drape" if you will, a surface over my curves, and I have tried every tool in the book, as well as different approaches, but I never seem to be able to get a smooth surface.

       

      I would appreciate it if someone could take a look, and tell me what I am doing wrong, or give this a shot, and post the file of your method?

       

      Thank you all for any help you might be able to offer, or ideas!

        • Re: Archtop Guitar..Still can't get it right....driving me nuts!
          Ravi Teja

          Hi John,

                              Please see the attached file and comment.The curves can be modified (if thats an option) to get better surface.

           

           

          Regards

          Ravi T

          • Re: Archtop Guitar..Still can't get it right....driving me nuts!
            Matt Lombard

            You can't do this correctly (in SolidWorks) in a single feature. What Ravi showed is fine if you're just looking for an approximation, but the attached image shows 3 places where it is wrong. You can't get the curl around the outside correct using a single Boundary feature. I notice the concave spot is caused by the original curves provided.

            wrong.png

             

            The curvature that comes to a point does so on both ends. This is maybe an ok first approximation, but you can't really use this technique to get it right. The curl goes around the whole body, but the feature is set up from a grid, and the grid changes relation to the curl. That kind of thing never works. So You put it in, and then you take it out, and recreate the curl in some other way that goes around the whole body - use a method that flows the way the geometry flows.

            better.png

            In the center, you're ok with the XY grid until you get to the curl, then you need a second feature to flow around. The center area was made with a 3 sided degenerate boundary, the way you set it up. But I cut off the degeneracy (where it all comes to a point), and made a second boundary of two closed loops. There's a ruled surface in there used as an angle reference to get the curl without doing a lot of sketching.

             

            I can see too that you are trying very hard to constrain splines. Maybe too hard. I used all 3 pt splines with handles. I try to avoid internal spline handles. I've had them freak out on me too many times, changing the shape of the spline without warning.

             

            Anyway, I would be more careful about the shape of the trimming spline (sketch2) if this were anything but an example.

             

            Best of luck.

            • Re: Archtop Guitar..Still can't get it right....driving me nuts!
              John Withers

              Thank you Matt and Ravi, for taking the time to work with this.

               

              Yes, I began to realize that trying to constrain the surface in all the directions you mention, was something which was not going to work.  I also needed to work on my curves better, and I am doing that now.

               

              Like you mention, I will need to deal with each segment seperately, and then stitch the whole thing together. In areas where I need a better blend, I will probably delete small areas and then patch to achieve a better result.

               

              I never reall though that something like this will take the amount of work it does, not that it would be so complex.  Modeling a car seems easier than this!  LOL!

               

              It even gets more interesting, since the bottom of the surface, will now also need to vary in thickness from the re-curve, to the center.  Which means it needs to be constructed seperately again, and then lofted...and that is only for the top of the guitar, as it would require an equal amount of effort for the back!  WOW!  LOL!

               

              Anyone have a laser scanner I can borrow for a week?  :-)