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Generating Line Elements from Exported IGES Curves


Malcolm Crowe

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This is a tip for generating complex "Line Element Models" as a single part for structural analysis purposes (such as within NEI NASTRAN for IRONCAD).

 

Creating line element models of complex lattice structures using the "3D Curve" tool within IRONCAD isn't practical.

 

A better way is to first construct these complex models as solids or surfaces (which can be parametric) and then extract the 3D curves from the faces using the "Extract Curve" tool.

 

However, when the model becomes very complex with many faces, rather than selecting all of the faces for extracting the 3D curve, it is easier to export the solid or surface model as a "curve" IGES file, and then import back into IRONCAD (or other CAD or CAE software).

 

Attached is an IRONCAD 2013 PU1 file demonstrating what is possible. In this I have constructed a part model of a lattice section using surfaces. This is parametrically driven with 3 design variations.

 

I have then created a new part within this same file, where I have copied bodies from the first part. That is, I have copied 2 bodies (one after the other) using Design Variation 1, and then copied bodies using Design Variations 2 and 3. I have then used the Tri-Ball to position these bodies relative to each other.

 

This second part (which now consists of 4 "Copied Bodies" from the first part) can then be exported as an IGES file. It is important that the output format is "curve" and that all surfaces are exported as NURBS. This is important if you want split faces to be exported as curves.

 

Having exported this IGES file it can then be immediately imported back into IRONCAD as a single line element model (even though it was created from 4 bodies). This is shown in the 3rd created part within the attached IRONCAD model.

 

This principle can be used with both surface and solid models, and can be applied to any type of application where line element models are needed.

 

NOTE: Wherever edges of "separate" bodies meet there will be duplicate 3D curves overlapping each other in the resulting line element model. These duplicate lines can be deleted within the 3D Curve edit tool by selecting the overlapping line segments and pressing delete. In the attached example I have avoided this by avoiding duplicate edges in my surface model.

 

I hope that this is helpful in demonstrating what is possible.

Generating_Line_Elements_from_Exported_IGES_Curves_130724.zip

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Good feedback!

 

One additional note, you can use a structured part and extract 3D Curves. The only difference in this approach compared to Innovative parts, is that the 3D curves will update as the solid is modified under Structured parts. So it can save some time in recreating the curves due to modifications (however it is a structured part and this is a bit more complex to learn).

 

Best Regards,

Cary

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Good feedback!

 

One additional note, you can use a structured part and extract 3D Curves. The only difference in this approach compared to Innovative parts, is that the 3D curves will update as the solid is modified under Structured parts. So it can save some time in recreating the curves due to modifications (however it is a structured part and this is a bit more complex to learn).

 

Best Regards,

Cary

36454[/snapback]

 

Hi Cary. This was my original approach. That is, extracting the 3D curves within the structured part so that the 3D curve would change with the model. However, NEI NASTRAN for IRONCAD wouldn't allow me to select these 3D curves (for meshing and setting of line element properties) when they were within the structured part. I could only get it to work when the 3D curve was a separate part. Malcolm

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