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parametric dims in extrude sketches

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    #1

    parametric dims in extrude sketches

    To create a timber frame family, I need to precisely notch the timbers.
    To control the dimensions with parameters, length, width, depth, there is no problem.
    And then flexing the dimensions works just fine.


    Now when I want to make notches in the extrude profile and control the sketch with parameters,
    I get a "constraints are not satisfied" message on attempting to flex the parameters.
    In this case setting 'a = 27' in the parameters properties dialog box.
    And the only option offered is to remove the constraints. What should I be doing?
    Attached Files
    Tags: None
    #2
    The main thing here is you should be using reference planes to constrain your geometry - not applying constraints directly to the geometry. Next up, because you have an angle in there that you wish to control (although indirectly through linear dimensions) you need to use a reference line. I've attached how it should look with the reference line and the required constraints. Create the reference planes first, then the reference line between the constraints and lock the reference line to the reference plane as soon as it is created. Once you have the reference planes and line flexing properly then create the sketch and lock to the references you have created.

    Note: I'm not sure what's going on in your other views so I haven't created any sort of constraint for the width parameter.
    Attached Files
    Michael
    Canberra, Australia

    Comment

      #3
      Hi Exar Khun. Thank you very much for the info. So reference planes is the way to go.

      There are four bevels in a main brace in the traditional French truss, plus the tenon.
      So that is going to be quite a few reference planes. I may be able to use just one per bevel.

      An angle and a distance would be my first choice. Just used 2 distances thinking that the
      angle might have been the problem. I coudn't open your file as I am using RAC 2011.
      Any way you could pack the file in 2011 readable format?

      Anyway, I'll hack it out, and let you know. Could take a while. Thanks again.

      Comment

        #4
        getting there

        OK Following your advice, I was able to get the first cut to flex nicely.
        This was done by using a reference plane to position the starting point,
        and a reference line to define the angle of the cut. Parameters for each.

        Now the method gets stuck when it comes to a second cut.
        I was not able to move the 'b' plane by changing its parameter.
        I get the same 'constraints not satisfied' message. See attachments.

        Also; what can I do to have the sketch and reference lines be less thick?
        I found how to control text size, but not line thickness.
        Attached Files

        Comment

          #5
          You just need more reference planes and reference lines, draw them first then draw your geometry using them. Draw your horizontal and Vertical reference planes first, then place your reference lines starting at those intersection. This will make the RL pivot off the RPs. See attached.

          Capture.JPGCapture1.JPG

          Edit: Also, be sure that your cuts alphas don't cross because that will break the geometry because, well, it's a different shape with a different number of sides.

          Edit2: To control the thickness of the reference planes, just do the majority of your modeling with Thin Lines turned on. If it's not on your options bar, it's in View/Graphics/Thin Lines.
          Last edited by AHutchinson; March 5, 2012, 05:34 PM.
          Adam Hutchinson
          Engineer in Training
          Integrus Architecture, P.S.

          Comment

            #6
            It worked very neatly. Was able to reproduce the procedure
            and expand it to all the notches with all the equatoins.
            Will post result shortly. The key is to use reference planes and
            lines as necessary, and lock everything like crazy. Works to a T.

            Thank you so much. I appreciate your taking the time and making
            the effort. Thin lines work like a charm. What a relief.

            Still having trouble defining one plane as paralel to another if the
            other eventually moves. The first should follow.

            Also, is there a simple way of locking sketch lines to planes?
            When I try to grab the lock, it disappears, so I exit, come back,
            and move the line away and back. Then I get to grab the lock.
            There must be a better way.

            Comment

              #7
              Originally posted by madhaka View Post
              Also, is there a simple way of locking sketch lines to planes?
              When I try to grab the lock, it disappears, so I exit, come back,
              and move the line away and back. Then I get to grab the lock.
              There must be a better way.
              To simply lock here is 2 options
              1. use the "pick line" tool and select "lock" in options bar (image 1). This way just pick Ref Plane and line will lock automatically.
              2. Use "Align" tool. Select "Align", select Ref Plane, select line, then lock. (image 2)
              Attached Files
              Mark Balsom

              If it ain't broke, fix it till it is.

              Comment

                #8
                But when you're sketching the lines the lock will also appear. Don't let it fool you, you can't select it. Only time that's possible while sketching is when you are using the rectangle command.
                Martijn de Riet
                Professional Revit Consultant | Revit API Developer
                MdR Advies
                Planta1 Revit Online Consulting

                Comment

                  #9
                  Great. Thank you very much indeed. Sure appreciate the efforts.
                  Looks like this is a good time to converse with those down under.

                  Don't you just love how nearly 3000 years after the greeks came
                  up with the concept, the word 'forum' takes on its full dimension.

                  Comment

                    #10
                    One timber done

                    Well to thank you for your input, and in the unlikely case you
                    ever need to draw a 12th century French timber-frame truss,
                    as opposed to the more modern and less massive Anglo-Saxon
                    truss, here is a post of the trigonometric solution for the cuts.

                    This is just one of the main braces, there is also a king-post
                    and the base member.
                    Attached Files

                    Comment

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