9 Replies Latest reply on Jun 22, 2017 10:53 AM by Nuno Marques

    Invalid geometry

    Nuno Marques

      Hi again, community!

       

      Back with my next issue. After successfully replicating a couple of 2D drawings to 3D parts thanks to you wonderful bastards, I am currently trying yet another. Seems simple enough:

      Fmv4G28.jpg

      However, note the red marked basic dimension. Whenever I try to set it I get an invalid geometry error.

       

      Part file with the sketch so far attached.

       

      Can anyone explain why I'm getting this error and maybe offer some help or guidance?

        • Re: Invalid geometry
          Jim Paige

          I believe that you have a dimension rounding error.  Basically, the dimension on the 2D drawing may say 11.29 but in reality it's more like 11.30422...etc.  I added a tangent constraint (red arrow below) to your sketch then added driven dimensions for the end radius and center location (yellow boxes) and then increased the decimal places so that the issue is better illustrated.

           

            • Re: Invalid geometry
              Nuno Marques

              I just noticed those 2 diagonal lines on the 2D drawing in the photo, right under the 93º angle to the left and again between the R30,8 and R14,2 (under the right side large hole). I'd never noticed this and don't know what that means. is it possible part of the sketch shouldn't be an arc but rather a straight line?

            • Re: Invalid geometry
              Dan Pihlaja

              Don't assume that the hole and the arc are concentric to each other.

               

              The circled points are fully defined, which fully defines the outside arc.

              The hole is also fully defined, which means that they cannot be concentric to each other.

              The drawing should have been clear on this (by not making the radius of the arc have an extension line to the center, among other things).

              • Re: Invalid geometry
                Nuno Marques

                Thanks Dan Pihlaja and Jim Paige. I'll keep this in mind moving forward.

                • Re: Invalid geometry
                  Dan Pihlaja

                  OK, I just tried to create this part from the print.  This thing is seriously over-dimensioned.  Even if you assume that NONE of the arcs are coincident to any holes.

                   

                  I would say that you have to pick and choose which dimensions to use.....or make nothing tangent to almost anything else.  This means that things are open to interpretation for the person modeling/manufacturing it.  Which is NEVER a good idea.

                   

                  Whoever drew this does not know what he is doing.  (Or was in a serious hurry and bypassed the checking process).

                    • Re: Invalid geometry
                      Nuno Marques

                      I couldn't tell you. I just find this stuff and use it to try and improve. I find I have learned a lot over the last few weeks since I started doing this. I knew close to nothing of CAD when I started. I feel I am improving considerably with this method and your help.

                        • Re: Invalid geometry
                          Dan Pihlaja

                          I agree...what you are doing is great!   Honestly, it is good practice in the beginning, once you have created a print of something......now have someone else try to model it using only your print dimensions.  If things go wonky, then there is something wrong with your print.

                            • Re: Invalid geometry
                              Nuno Marques

                              That's actually a great suggestion. I've been so worried trying to hone my modeling / drawing that I haven't stopped to think if they are correct. I have to find someone that's willing to "exchange" so that we can test each other's work. Thanks for the idea!