Two-Stage-Optimisation - Removing Material/Struts

The Advanced User Settings give the possibility to (re-)start an optimisation with a Start Space. With this option already optimised results can be modified, e.g. struts can be added or removed, and this new geometry can be used as the starting point of another optimisation. With this Two-Stage-Optimisation already optimised geometries can be highly influenced and steered in the desired direction.

In the following, the final result of a previous tutorial will be modified and a Two-Stage-Optimisation will be performed. In this case a strut will be removed.

Step 1: Transfer of the already existing geometry

The first step is to transfer an already existing geometry. The result from the following optimisation was used:

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The last iteration of the nominal geometry is selected and transferred to the Pre Processing with the Transfer Design Candidate Shape to pre-processing button. Open the Conversion Settings and select the option Facet. The selected geometry is transferred as a faceted solid to the Pre Processing.

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In general, every previous iteration can also serve as a Start Space and can be transferred.

Step 2: Removal of a strut

With the Sketching and Geometry Tools inside MSC Apex Generative Design a square can be created to remove one strut of the structure. The square is created by drawing a rectangle on the plane using the Sketching Tool. The Push/Pull Tool is then used to create the volume of the square.

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Tip: In some cases it is easier to create a plane first and then draw the rectangle or the Push/Pull Tool can be used to move the rectangle to the correct location to enclose the strut.

Step 3: Creation of the Start Space

To create the new Start Space the just created volume and the transferred optimised shape can be subtracted with a Boolean Operation.

It is not a problem if the square isn’t perfectly removing the full strut. It only has to disconnect the strut with enough distance for the algorithm to remove it. The optimisation will redefine the structure accordingly to the Boundary Conditions and Stress Goal.

The resulting faceted solid needs to be exported as an STL-file.
Attention: The unit has to be in meters!

Step 4: Start of the optimisation with the modified Start Space

In the last step the optimisation can be (re-)started with the new, modified Start Space. Therefore, the previous Scenario can be copied.

For the copied Scenario the Advanced User Settings have to be set-up. These are used to adjust the number of iterations for each Resolution Level. In most of the cases a Two-Stage-Optimisation should start directly on the highest Resolution Level or at least on the last two Resolution Levels.

For this tutorial the following settings are input:

schedule.level.0.iterationCount = 0
schedule.level.1.iterationCount = 0
schedule.level.2.iterationCount = 3
schedule.level.3.iterationCount = 3

schedule.level.0.eventSafetyCoefficient = 0.3
schedule.level.1.eventSafetyCoefficient = 0.4
schedule.level.2.eventSafetyCoefficient = 0.9
schedule.level.3.eventSafetyCoefficient = 1

schedule.startCandidate.candidate= <restart-file.stl>
geometry.startCandidate.path= <restart-file.stl>

Also, the path to the modified Start Space has to be selected in the respectable field.

The optimisation starts with the modified geometry as the first iteration. At the end of the optimisation the strut is removed and the rest of the structure completely integrated into the design. The algorithm might increase material elsewhere to compensate for the loss of the strut.

You can check the status of the optimisation in the GD Status and get more information on Warning and Error messages. This can be done directly in the Post-Processing as well as in the Studies tab for an optimisation that has already run.

The complete MSC Apex GD project with all results can be downloaded here:

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