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Training:

Relevant data for this tutorial:

Step 1: Reimport your already optimised geometry

The optimised geometry can be reimported into a new project or into the already existing optimisation project. For this Tutorial the project of the Bridge is used.

For a Retransition to a NURBS-Geometry a non-intersected optimisation result is needed. Therefore, the Smooth-Geometry from the Post Processing should be exported. The geometry of this file stays always inside the Design Spaces limits except of the Non-Desgin areas, they intentionally exceed the Design Space limits to enable always an easy and clean boolean intersection

After importing the Smooth-Geometry STL-file the optimisation result is displayed as a Faceted Solid inside the model tree.

Step 2: Mesh to CAD

With the Facet to NURBS Geometry Tool under the Geometry Edit Tools the STL-file can be transitioned to a NURBS-Geometry. Therefore, the Automatic Size Calculation and the Partition Preview can stay active. With the middle mouse button (MMB) the operation can be executed.

In a first step a preview of the partitioned quad mesh is shown.

If the partition looks satisfying the NURBS patch creation can be started. If finer, smaller patches are desired the NURBS Face size can be varied manually. Depending on the Geometry this step can take some time.

When the transition is finished, the status bar in the bottom left displays “NURBS is created based on partitioned Facet Body” and a new solid shows up in the model tree.

From time to time depending on the geometry some NURBS patches might fail. These will be displayed in the status bar as well. If this happens the geometry can be repaired manually. How this works is described here.

Step 3: Geometry Cleanup

We recommend to use the Geometry Cleanup Tools after the NURBS CAD-Geometry is created.

Step 4: Creation of functional surfaces and sharp edges with Boolean operations

To create the final CAD-Geometry all functional surfaces and sharp edges have to be created with boolean operations. The best way for this is a boolean intersection between the retransitioned optimisation result and the Design space of the optimisation. A copy of the Design space is needed for the following operation.

With the Transform Tool the Solid of the Design space can be copied by activating the Copy option and transforming with 0.

To create one solid without any cells or partitions the boolean merge function for cells has to be used. With this a Solid only for the Intersection with the NURBS Retransition is created.

The next step is a boolean intersection between the created NURBS Geometry of the optimisation result and the edited Design Space solid.

In some cases this intersection fails due to overlaying surfaces from the optimised result and Design space. In the picture below a critical area is displayed. What to do if this happens is described here.

The result is an intersected CAD-Geometry with all functional sharp edges and surfaces. At this point it is also possible to create machining allowances on functional surfaces which are post processed by milling or other manufacturing processes.

The finished Geometry can be used in any CAD software and for all further steps like a FE-Reanalysis with MSC Nastran.

The whole MSC Apex Generative Design project with the retransitioned intersected CAD-file can be downloaded here: