NURBS Retransition - Manual Intersection

For this Tutorial the project of the GD-Bracket with different complexities is used. The retransition of the final optimisation result of the second scenario is already performed.

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.

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.

If this happens the Design Space for the Intersection needs to be manipulated to make a boolean intersection possible. In most cases a reduction of the Design Space for the intersection is successful.

For this part all bore hole radii are increased by 1 mm from r = 5 mm to r = 6 mm.

Furthermore, the surface at the bottom is decrease (pushed) by -0.2 mm (in negative z-direction).

Now, the boolean intersection between the optimisation result and the modified Design Space can be performed.

The last step is to bring back the original dimensions for the bore holes and the down surfaces.

With the Push/Pull Tool all radii can be set back to r = 5 mm.

Moreover, the down surfaces have to be increased by 0.2 mm.

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 post processes.

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

Workaround: Boolean Subtraction

For some really complex parts it might not be at once clear which areas are the critical ones for the intersection. In these cases boolean subtractions can help to create the functional surfaces and sharp edges.

With the project sketching tool solids can be easily created from the Design Space which can be subtracted from the optimisation result.

The result of the boolean subtraction are functional surfaces as well as sharp edges.

The example geometry used here is from the GD-Bracket Tutorial. The input file is the result of the second scenario.