4 Replies Latest reply on Nov 10, 2008 12:41 AM by Paul McGarr

    Dimension Question

    Paul McGarr
      This might sound like an odd question, but I was burned by something a few monts ago, changed my dimension method, and now can't reproduce original problem. Let me explain...

      I've been using SolidWorks regularly for under one year now, so maybe I am asking something obvious, but I've witnessed weird behavior with dimensioning that I want to clear up. Maybe someone can clear this up for me. There are two ways to dimension a rectangle...click a line and place a dimension (length of side) or pick two lines and place a dimension (distance between paralell sides). Recently I dimensioned a rectangle using the first method and got burned by later adding a fillet and the fillet actually increased the length of the original feature. It appeared that SolidWorks maintained the length of the line (as I defined) and added material to the length of the rectangle to allow for the fillet.

      I'm bringing this up because I instantly changed my dimensioning to reflect the dimension between parallel sides to avoid this, but in the SolidProfessor courses I am taking, they use the single line dimension and it makes me wonder what I did wrong because I can't imagine someone teaching something that would be bad practice. Well, I can imagine, but you know what I mean.

      To straighten this out, I dimensioned a rectangle the simple way and added a fillet with no unusual result. I expected to have a problem like I described earlier, but everything worked as expected...the rectangle didn't grow due to the fillet.

      So, now I am trying to figure out what I could have done wrong, and to see if anyone has been burned by dimensioning line length as opposed to distance between sides.

      Any ideas what I might have done? What do you guys do? Maybe because I was new I didn't have the proper rectange with all the relations to avoid this behavior? Does this even make sense?
        • Dimension Question
          Roland Schwarz
          I can't imagine someone teaching something that would be bad practice.

          Happens all the time, especialy from teachers who are disconnected from reality.

          There is an option for sketch fillets that allows one to keep corner relations. Perhaps this accounts for the different behaviors you are seeing.

          I would stay the course dimensioning sides and not corners or endpoints. This is generally more robust, and also truer to design intent in most cases.
            • Dimension Question
              Paul McGarr
              Roland, thanks. I'll have to get farmiliar with that option, but it sounds like you might be on to something.

              I figure the way I started doing it was a safe bet, but I always like to know WHY I do something. I never settle on something "just because". That's why I posted this. I want to be sure I understand fully.

              Thanks again.
            • Dimension Question
              John Lhuillier
              I've had that happen when dimensioning drawings. We had an existing part/drawing that I used for a new part and added a chamfer to the bottom of the plate. The drawing was dimensioned using the single line on the side and it repositioned the dimension to show a shorter base plate because of the addition of the chamfer.
                • Dimension Question
                  Paul McGarr

                  John L'huillier wrote:

                   

                  I've had that happen when dimensioning drawings. We had an existing part/drawing that I used for a new part and added a chamfer to the bottom of the plate. The drawing was dimensioned using the single line on the side and it repositioned the dimension to show a shorter base plate because of the addition of the chamfer.

                  Ahhh! That's what it was. Thanks for posting because that jogged my memory just enough for me to remember.

                  So, caution to anybody that is unaware of this...it can be painful. Hopefully this will help someone else.