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Thread: Creating a simple precast family - not so simple!

  1. #1
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    Creating a simple precast family - not so simple!

    Hello, this is my first post on here, though I have been using Revit for some time.

    I have to create a precast riser family that has dropstems (in pink in the images) and a slab part. The dropstems are cut back shorter than the slab for bearing on a concrete beam.

    So far I have tried extrusions, generic models, sweeps, and I also opened up a double tee in Revit and dissected it to see how it works and used that.

    What I need is a beam family (so I can cut geometry in plan with reference planes) that has grips for the length, and also grips and different lengths for the dropstems.

    It seems like I have to have the drop stems be a separate family, so I can control the lengths accurately, but I would much rather have the one family.

    Having trouble with the grips, the parameters, and other things too. so if anyone knows a good resource for this, that would be great.

    Thanks!
    Attached Thumbnails Attached Thumbnails 3.JPG   2.JPG   1.JPG  

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    Hello!
    Separate family, then combining into one element using assemblies or parts.
    Why do you need it as one family?

  3. #3
    Forum Addict Andres Franco's Avatar
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    Quote Originally Posted by Dlowery View Post
    I have to create a precast riser family that has dropstems (in pink in the images) and a slab part. The dropstems are cut back shorter than the slab for bearing on a concrete beam.

    So far I have tried extrusions, generic models, sweeps, and I also opened up a double tee in Revit and dissected it to see how it works and used that.

    What I need is a beam family (so I can cut geometry in plan with reference planes) that has grips for the length, and also grips and different lengths for the dropstems.

    It seems like I have to have the drop stems be a separate family, so I can control the lengths accurately, but I would much rather have the one family.

    Having trouble with the grips, the parameters, and other things too. so if anyone knows a good resource for this, that would be great.

    Thanks!
    Hello, as previously said by Nurlan, separated families can do the trick, that way you'll have less reference planes and less problems.

    you've also mentioned that you need some grips to control the length of the family, you can achieve this by using reference planes set as "Strong Reference" and by adding a length parameter "by instance", this allows you to have those grips that you need to pull the dimensions of your beams without duplicate each time, if you want those grips to be visible in 3D don't use reference plane but Reference lines.

    I strongly recommend you to set the reference planes and the dimensions before to model the extrusions that way you can test if your constrains are working or not, hope this made sense

  4. #4
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    Thank you Nurlan and Andres!

    This technique works.

    However, I have am having other problems. Maybe you can answer some questions. I'll try to be as specific as possible.

    Here is basically what I did to create this: File: New Family: structural beam type...

    I went to the left view, deleted the square generic beam and picked create extrusion. While in Sketch Mode, I drew reference planes, dimensioned and locked (blue dimensions), all my chamfers, then dimensioned and added labels (red dimensions) THEN I drew all the lines, snapping to reference plane intersections, then pulled the lines off the reference planes then back to them and locked them, and finally clicked finish sketch.

    When I load it into a project and try to change a parameter, it usually blows up and Revit has to delete it to resolve the issue, or if I can change a parameter, my chamfers stretch. I thought they were locked in with the blue dimensions.
    Attached Thumbnails Attached Thumbnails 1.JPG  

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    Reference planes can be locked to each other only when they are parallel. Your chamfers won't stay 1" and 3" when you change stem thickness. Try with reference lines instead of reference planes, they work similar to regular lines, so their end will remain together, also you can create dimensions between their end intersections unlike ref planes.

    you can try to modify the parameter values in the family editor and figure out what's wrong before loading to project. With this plugin you can add random values to parameter so you can check if it works with strange values: https://apps.autodesk.com/RVT/en/Det...80106470667663

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    Forum Addict Andres Franco's Avatar
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    Quote Originally Posted by Dlowery View Post
    ... While in Sketch Mode, I drew reference planes, dimensioned and locked (blue dimensions), all my chamfers, then dimensioned and added labels (red dimensions) THEN I drew all the lines, snapping to reference plane intersections, then pulled the lines off the reference planes then back to them and locked them, and finally clicked finish sketch....
    I'll have a tendency to draw all my Reference planes or Reference lines OUT of the Sketch mode! is a way simpler to test if your "Future Sketch" will work or not, otherwise you'll find the same problems!!

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    I sometimes wonder why there are so many techniques for this. I have seen plenty of videos that recommend NOT using reference planes, and currently, my family has none and it seems to work perfectly, not to mention it looks cleaner. I wonder if it's going to bite me later.

    Another question I have is about the family crashing. If a parameter is set to an invalid value in the main project, it gives an fairly unintelligible warning and deletes the instance of the family. Is there a way to generate the warning myself, such as "concrete slab cannot be less that 2" thick."

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    Moderator Robin Deurloo's Avatar
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    Quote Originally Posted by Dlowery View Post
    I sometimes wonder why there are so many techniques for this. I have seen plenty of videos that recommend NOT using reference planes, and currently, my family has none and it seems to work perfectly, not to mention it looks cleaner. I wonder if it's going to bite me later."
    I would really wanna see those video's, because thats the dumbest advise anyone could give.

  9. #9
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    Quote Originally Posted by Robin Deurloo View Post
    I would really wanna see those video's, because thats the dumbest advise anyone could give.
    Yep! Ref Planes OUTSIDE of Sketch, so they can be used for multiple things.

    No RP's = Family goes in trash (yes, it will bite you later, in one of any number of ways...).

  10. #10
    Mr. Revit OpEd
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    Build the Bones (ref planes/lines), attach Muscle (dimensions/parameters) then add the Skin (solids/voids/lines).

    That word..."simple"...so rarely does it mean what we think it means (cue Inigo Montoya).
    Last edited by Steve_Stafford; August 7th, 2019 at 05:52 PM.

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