6 Replies Latest reply on Mar 25, 2009 5:02 AM by Matt Lombard

    self-intersecting surface

    John Kreutzberger
      This topic is cross-posted from the surfacing forum.

      I have an imported part that I am doing a core/cavity split for. I kind of use the mold tools, but not completely. I have all of my knit surfaces for core, cavity and parting surfces in the part file but for a few reasons that are not relevant to my problem I choose to do my split in the context of an assembly.

      I create my core and cavity blocks in this new assembly-then bring in the molded part and position it. I then edit the core and copy the core surface and the parting surface; knit them together and do my surface cut. No problems.

      Then when I try to do a similar thing for the cavity, I get an error message when I try to offset the cavity surface by a distance of zero: resultant body is a self-intersecting surface. News to me. I go back to the part and look it over and find no problems. Then I try to offset that same surface in the part file-just for grins. No problem-no error message-everything looks fine.

      I go back to the assembly and edit the cavity part and try to offset either one of these surfaces with no success. Anybody have any ideas on what is going on? A body check shows no problems, by the way.
        • self-intersecting surface
          Mark Biasotti

          In order to understand this of course it would help to have the file posted or an example. If it is propietary, you can send it to mbiasotti@solidworks.com and I'll have a look at it for you. If it's too big email me and I can provide for you an FTP site.
            • self-intersecting surface
              John Kreutzberger
              Thanks, Mark. I cannot post this in a public forum, but both the part and assembly should go through with an e-mail. I have other ways to get this job done, but cannot figure out why I cannot copy a surface when editing in assembly, but can copy the same surface within the part file.

              I appreciate your help with this.

                • self-intersecting surface
                  Matt Lombard
                  are part and assembly units the same?
                    • self-intersecting surface
                      John Kreutzberger
                      Hi Matt,

                      Yes-in a way they are. The part is set to custom with inches as the length unit. The assembly is set to inch,pound second.

                      I tried matching all of that up exactly but the cavity surface will still offset by a distance of zero in the part file with no problems but when I edit the cavity insert and try to copy the same surface at a distance of zero-it errors out telling me that the result is self-intersecting.

                      As usual for a SW error message , there is no arrow pointing to the problem area. I have never been able to figure out how the software can know there is a problem but can't show you where it is.
                        • self-intersecting surface
                          John Kreutzberger
                          OK-so I had to do it the SW way. I don't usually create the solid bodies in the part file and copy them out, but that worked just fine. That tells me there is nothing wrong with my geometry. Everything knit together and the SW feature worked as advertised-I just don't like to do it that way. I am still not understanding why there was a glitch in using my quirky personal method for the split, but SW wouldn't let it happen this time-although I must have split at least 200 parts my way before this.

                          My reason for wanting to copy the surfaces and do the cut in the sub-assembly is that I am fussy about the origin of the core and cavity part files. Imported parts often have the origin off in left field someplace and that was the case here-plus the fact that the planes were rotated from how we will mold the part.

                          Onward and forward. But I am still interested in why I couldn't copy the surface.......