3 Replies Latest reply on Jul 29, 2013 3:32 PM by Tom dunn

    The Shell From Hell.....

    Joel Rapoport

      hello all,


      im having some trouble with a part I am designing.

      this part is made by surfaces, and after making it a solid im trying to shell it to 2mm thickness with this surface open:

      each time im making some changes-im having problems in different surfaces....

      I also tried splitting it in different places but with no results.

      these are the areas that I usually have problems with:


      so I tried changing the lofts, splitting the original single loft to 2 lofts and a boundary between them (you can see it in the part features) but now the shell is showing me problems in different areas.

      im pretty frustrated.... this is not the most demanding and complicated surface ever made but im having a whole lot of shell problems which is burning up my time. I really need to go forward with this project and im getting stopped by this problem.


      I usually try to offset the surface after I do it to 2mm offset in the direction of the shell to see if I will have problems. usually it does produce the offset, but sometimes the offset looks "bad" and deformed. I guess that's why im getting the problem shelling.


      my main problem I guess is that I don't see (or understand) where is my problem. the lofts that im making look fine to me so I don't really see what im doing wrong and why im getting all these problems with shelling. I have done in the past parts that are much more problematic surface wise and I didn't get so much hassle.


      if anyone can help me with some pointers it will be great.

      if you want to download the part and play with it I would really appreciate it (I'm running SW2011).


      with thanks in advance,


        • Re: The Shell From Hell.....
          Jerry Steiger



          I'm still on 2010 so I can't open up your part. Have you tried offseting individual faces, then sets of faces to see if you can isolate the problem? Have you checked the radius of curvature? You might also try switching Lofts to Boundary Surfaces, as they tend to cause less problems. (Although there are the rare occasions when a Loft will work better than a Boundary.)


          Jerry S.

          • Re: The Shell From Hell.....
            Theo Holtzhausen

            It's not liking the fact that the loft you're pointing at is recessed 1.3mm. When I suppress Surface-Extend 64 it shells fine but then there's no recess. Before suppressing this feature the minimum radius of curvature is 0.04mm and after suppressing it's 0.4mm. Below is a band aid way to get something close to what you want. This is probably not the right way to do it but you may have to pull similar tricks to get the geometry you want.


            - Shell without the recess


            - Create plane and sketch above the part and convert entities of the edges of what will be the recess


            - Knit surface to offset from


            - Extrude, offset from surface


            - Cutt extrude, offset from surface


            • Re: The Shell From Hell.....
              Tom dunn

              Hi Joel it looks to me that solidworks is having a tough time with the inside lip. SW does not know what to do with the surface in dark blue. What I am trying to show is I took a section on the front plane then started to offset surfaces to the inside of the part by 2mm (shown as 3 light blue lines). The dark blue surface gets eliminated. I think that is where the error is coming from.