topic Re: Thickness variation_STEP file in Moldflow Insight Forum

Thickness variation_STEP file

Anonymous — Wed, 08 Feb 2017 13:17:40 GMT

Hello,

when importing STEP file to Moldflow, thickness of the part varies from actual CAD part. Has any one faced similar issue?

How can this be resolved. Even tried importing through simstudio, the results are same.

with stl file, the thickness looks good, but the geometry of part especially in radius is bad.

Best Regards,

Anoop

Re: Thickness variation_STEP file

bernor_mf — Wed, 08 Feb 2017 14:15:11 GMT

Hi Anoop,

I have not seen this, and that is Step from Catia V5.

The geometry had quality issues, so fall back to using STL mesher.

This might cause coarser mesh hence thickness issues.

In which order of magnitude is the thickness difference is CAD vs Moldflow mesh on Step imported geometry?

Could you try to export the mesh to patran format and re-import and check thickness if still the same issue?

Regards,

Berndt

Re: Thickness variation_STEP file

harald_goetz — Wed, 08 Feb 2017 22:04:57 GMT

Since you mention that the deviation can especially be seen in radii, I'm pretty sure this is because of the way thickness is determined in a triangle mesh.

From what I know the thickness is determined by taking a face (triangle in STL) and go in the negative normal direction and looking for the opposite face.

Since the mesh is an approximation of the original CAD file there *must* be an deviation, but usually "under the radar".

Let us know the numbers or show some pictures - then we are able to determine where the problem might be located.

HTH

Harald

Re: Thickness variation_STEP file

Anonymous — Thu, 09 Feb 2017 21:33:26 GMT

@Anonymous check whether the STEP file you got is solid model without any open surfaces to it. normally STEP files from CATIA should have this issues due to surface loss or some open surfaces. have couple of questions to you...

1. which software you exported that STEP file..?

2. did you check with *.xt (parasolid format)..?

3. how you are meshing the part..? (using design link while importing or import model 1st & meshing it in moldflow)

Re: Thickness variation_STEP file

bernor_mf — Thu, 09 Feb 2017 21:54:26 GMT

Hi @Anonymous

another way to sometimes workaround CAD and meshing related issue is to import the cad-file, such as step, to SimStudio Tools, and then export to .sat-format and import to Moldflow Synergy. SimStudio does some fixing, and even if not doing Autofix in SST you can actually get an improved geometry quality for mesher.

Give it a try, and share your findings.

Maybe 2017.3 Automatic mesh sizing for CAD models might help in this issue as well.

Regards,

Berndt

Re: Thickness variation_STEP file

Anonymous — Wed, 15 Feb 2017 10:36:56 GMT

Hi Berndt,

Thanks for your reply.

Often i face this thickness issues when importing as STEP file. One reason can be some unpatched surface in CAD geometry. we are trying to fix some surfaces in CAD & see what the outcome would be.

For the present part the magnitute of thickness variation is high (difference from 1mm to 2mm from nominal CAD thickness).

I have tried to import the part through simstudio, still the results was same.

Best Regards,

Anoop