Flat Layout of pipe question

Tim Neumann
Tim Neumann
in BricsCAD Mechanical

This one is a "out in the weeds" type question.

In Bricscad how do you set the parameters for unfolding a pipe? What about K factor?

For an example I extruded a 2" pipe (2.375" OD x 0.154" thickness) turned it into a sheet metal part and added a single break line. When it unfolds the material width is 6.95". The circumference of the pipe OD is 7.46", is there supposed to be that much of a difference from the unfolded width? Any insight on this would be appreciated thanks!

Comments

  • Virgil
    Virgil

    Hello.

    Most likely, after converting to sheet metal, a lofted bend was created.
    Lofted bends are unfolded in a different way, not like regular bends which use a k factor or a bend table.

    For lofted bends, the base of calculation is the median diameter, which is 2.221" in this case.

    To see the parameters available for unfolding lofted bends, select the lofted bend in Mechanical Browser and notice the lower side of the panel - there are some properties listed there.

    Mainly, it is about the number of subdivisions and the unfolding mode.

    In my testing, by default, there were 10 subdivisions and the analytical mode.

    The analytical mode assumes a formula like L = PI * D.
    For Dm = 2.221", the length is L = 6.977"
    Considering the split in the pipe - in my case sp = 0.018" - the final length is Lf = 6.959" or 6.96" when rounding to 2 decimals.
    There could be some small differences in values if you got 6.95".

    Further, you could experiment with adjusting the number of subdivisions and other unfolding modes.
    Triangulation and Quadrangulation approximate the circle with a polygon whose number of edges is equal to the number of subdivisions.

  • Tim Neumann
    Tim Neumann

    Thanks Virgll for making it "plain". I'll try the different options just to see what it spits out.

  • RSW
    RSW

    Another quick option could be to create a fake sheet metal object to unfold the pipe.

    Assuming you use a circle and a centreline to create the pipe… then also create a square (or rectangle in case of an oval pipe) that has the same dimensions as the pipe, in your example a square of 2 inch by inch.

    Extrude that square over the centreline, convert it to sheet metal and then use the sheetmetal unfold command.
    There is one catch depending on which version of BricsCAD you are using, if the version is 22 or higher it no longer gets is right at first conversion of square extrusions as the first conversion will have the face perpendicular to the the actual bend direction/path. In that case convert to sheet metal again and you will get the faces correct, then dissolve the face perpendicular to the bend path and then you can unfold like normal sheet metal. (Versions before V22 got converting extruded/swept squares with bends right at first conversion every time, so what has been changed since V22 is a mystery to me).