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Drawing HVAC flexible duct in 2D

Where can I find how to draw circular flexible ductwork in BricsCAD 2D or 3D


  • Charles Alan Butler (CAB) has created a Lisp program for this: Flex Duct Creator. It is available at (you have to log in to be able to download the zip-file).

    An alternative is to use a special linetype as demonstrated here.

  • Two options for creating a simplified 3D duct.
    1. For a simple run use LOFT with the setting ‘normal to both ends’ (set LOFTNORMALS = 4). You need a CIRCLE at each end to create the duct, no need to create a guiding line.
    2. For more involved runs you can use DMTHICKEN in conjunction with a SPLINE, making sure that the spline tangency at each end is parallel to your connection. Using a SPLINE allows you to go up and down in the Z axis.

    I also found previously found DMTHICKEN was useful for modelling metal spouting.

    Jason Bourhill
    CAD Concepts

  • Here is the ZIP file.

    Flex 23
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Origami is the Japanese word for paper folding. ORI means to fold and KAMI means paper and involves the creation of paper forms usually entirely by folding.

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