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The Mesh to CAD functionality is transitioning the optimisation result from an STL-file back into a NURBS CAD-file. Therefore, a surface quad mesh is modelled on the optimisation result geometry and patches for bigger planar surfaces are merged intelligently.

The Retransition should be performed on a non-intersected optimisation result. After the Retransition a boolean intersection with the Design Space can be done to create all functional surfaces and sharp edges. The resulting NURBS CAD-Geometry can be manipulated by MSC Apex (Generative Design) or any CAD software. The Retransition ensures and simplifies the continuing workflow to the FE-Reanalysis, further CAD modification and process simulation.

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The workflow to achieve this transition is as follows:

1. Import a non-intersected optimisation result. You can find this file in your project folder: Project → Meshless Generative Design Scenario 1 Step 1.v1 → buildSpace_MC_MainData_Loop_64.stl

2. Create a NURBS CAD geometry with the Facet Body to NURBS Geometry Tool (Geometry Edit Tools)

   1. Let the software determine a suitable Quad-mesh size

   2. Choose your own suitable Quad-mesh size

3. Nurbs not fully generated. Status message: …

   1. Use Geometry Cleanup tools

   2. If necessary use the Filler tool to restore missing NURBS-Patches

4. Boolean Intersection between the NURBS geometry and Design Space either in MSC Apex Generative Design or MSC Apex

You can find a step by step tutorial here.MSC Apex Generative Design is a design generator. Thus, to verify the results a reanalysis with a high precise FE-Analysis Tool as MSC Apex (Nastran) should be done after deciding on a design. We recommend a reanalysis for all critical parts to include the relevant boundary & overload conditions that aren’t taken into account during an optimisation.

There are two ways to realize a FE-Reanalysis. One based on the created STL-file and another by creating a NURBS-Geometry (Retransition). For both methods an intersection has to be done to create functional sharp edges and surfaces on which the boundary conditions can be applied. Either automatically during the optimisation or manually with MSC Apex Generative Design. Since major improvements regarding speed and robustness for the Retransiton and the following intersection, the NURBS-Geometry workflow is recommended.

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NURBS-Geometry Workflow

1. Create a NURBS-Geometry with the Facet Body to NURBS Geometry Tool. We recommend to use a non-intersected geometry for this. Therefore, the smooth geometry can be exported from the Post Processing.

2. Boolean Intersection between the retransitioned NURBS-Geometry and Design Space either in MSC Apex Generative Design or MSC Apex.

3. Import the NURBS CAD-file to MSC Apex.

4. Remesh the geometry with a solid mesh (Tet-elements).

5. Apply the boundary conditions

   1. Make sure that the applied boundary conditions are the same as in the optimisation (Loads are applied as RBE3 elements and fixations as RBE2 elements)

STL-file Workflow

1. Export a design candidate from the Post Processing.

   1. Make sure the intersected geometry is used. Otherwise a manual intersection needs to take place in MSC Apex Generative Design or MSC Apex.

2. Import the intersected STL-file into MSC Apex as a mesh.

3. Use the Geometry-from-Mesh tool to create a faceted body.

4. Delete the imported surface mesh.

5. Remesh the geometry with a solid mesh (Tet-elements).

6. Apply the boundary conditions:

   1. Make sure that the applied boundary conditions are the same as in the optimisation (Loads are applied similar as RBE3 elements and fixations as RBE2 elements)