Workflow for importing truss geometry from CAD?

IshmaelIshmael
I have a handful of existing truss structures that I wish to compare, similar to this

or this:
http://mecway.com/forum/discussion/423/nonlinear-3d-with-beam-elements-for-spaceframe-car-chassis

They are built using the Solidworks 3D sketcher, which I can export to STEP and open in FreeCAD. However, Mecway only imports solids from STEP files, not lines or curves.

If I want to avoid re-building each truss using the Mecway modeller, which of the formats that Mecway imports will capture this type of geometry, and how can I produce these files? The Mecway manual indicates that it can import UNV files, which is listed as an export format in FreeCAD; however FreeCAD fails to actually export a UNV file. I suspect I am missing a step.

Has anybody done anything similar, and can share their workflow?

Comments

  • SergioSergio
    edited August 2017
    My last project using beams was a pain also, all do it entering the node coordinates for every corner, then unity this nodes to create the beams and then refine it every segment. A real pain
  • VictorVictor
    DXF would usually work for this but apparently SW didn't export 3D DXF in 2011 but maybe does now?

    https://forum.solidworks.com/thread/50774

    Here are some suggestions for exporting a list of point coordinates. You would be able to import that as the very simple .xyz file format in Mecway but would still have to add the elements by hand as Sergio said.

    https://forum.solidworks.com/thread/21628

  • IshmaelIshmael
    Thanks for your quick responses Sergio and Victor

    It sounds like if I can find a way to produce a 3D DXF using whatever tools I can get my hands on, then the wireframe geometry from that file will appear in Mecway?
  • VictorVictor
    Not guaranteed. Mecway only supports some common DXF shapes as listed in the manual. Though a structure like this is probably going to become LINEs which are supported.
  • rhokarhoka
    better use DXF file when doing analysis with beam/truss element, just use LINE command in CAD programs.

    in MW you can assign section element then changing the properties to truss from icon menus.
  • StefanHStefanH
    Hi. New to Mecway and just started using. Seems easy enough to get lines from 3D model: 1. Create multibody Step-file with parts interfaces where need lines. Import the STP file into MW.
    2. Mesh as surface with quad dominant, min. no elements per curve and edge =0, size grading set to aggressive (few elements).
    3. This will give large elements with nodes and edges in all required line locations. Delete any extra elements if you wish to clean up but not required.
    4. You can create new component and create new 2D elements clicking on the nodes you want with the mouse. You can then delete the original mesh component from step 2. if you don't need. Apply properties to the 2D elements and refine as usual.
    Instead of step 4., you can also Edit -> delete elements and retain nodes, to build the 2 D elements, but the elements in step 4. give visual structure better than just nodes.
  • StefanHStefanH
    Also works with 1. Create Step-file from CAD model with surfaces split from eg. the sketches. The split surfaces (faces) come into MW step import fine.
  • ehouleehoule
    I don't know if it could help someone... but usually from solidworks , I delete all my solid bodies so that only the 3d sketches remains. Then I export in step format (using option to export wireframes). Then I open the step using freecad and then freecad could export 3d dxf (even if it is written 2d dxf in the description...)

    I could then use the 3d dxf in mecway and it works fine
  • SergioSergio
    Just to share my procedure, have worked months ago with roll cages made of tubes. The best way that I found was to model the assembly as wires in FreeCAD, using standard 2D sketchs for the tubes lying in a plane (most of them), and 3d curves (Dwires) from the Draft module for the bended tubes that not lie in a plane. After that export all the curves as step, and do a 1D mesh in Salome, then export as UNV and import in Mecway to apply sections, materials and boundary conditions. Sounds complicated, but once you catch it is very quick, and you can trace the image on FreeCAD and Mecway as well.


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  • SergioSergio
    I will try to export as 3D DXF as @ehoule says, maybe the Salome meshing could be avoided.
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