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To set up these additional parameters, the Input Commands (left side of the table) need to be added to the optimisation model in the Advanced User Settings Text Field. In the picture below an example is shown. By adding these Advanced User Settings, the first (coarse) resolution level will be skipped and the optimisation starts directly at the second level. You might want to add more iterations to the remaining levels to give the optimisation the chance to reduce the material accordingly and reach a convergence in each level. Especially level 2 can use more iterations in this case.
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Restart (Start Space)
With the Advanced User Settings a Restart is possible. A Start Space needs to be chosen with which the optimisation will re/start.
Therefore, an already optimised STL-file is needed as a Start Space. This can be exported directly from the post processing and be selected as a Start Space by clicking on the browse button. Therefore, the unit of the exported STL-file needs to be in meters (SI-Units). In most cases the Strut Density and Shape Quality settings must be changed as well using the Advanced User Settings. For a restart the same resolution level and number of to be completed iterations have to be filled in. You can find a Tutorial to how to perform a Restart here.
Advanced User Settings Commands for a Restart with Start Space:
schedule.startCandidate.candidate=<restart-file.stl> geometry.startCandidate.path=<restart-file.stl> | Specifies the Restart/Start Space file. Provides the information for the correct path to the Restart/Start Space file. |
This way a two-stage optimisation is also possible. For a two-stage optimisation the resolution level and number of iterations must be chosen wisely and will need some fine tuning.
A Start Space can be marked as a Non-Design Space, thus the Start Space cannot be removed during the optimisation and will be part of the final design. Therefore, the following commands (where StartCandidate is the name of the Start Space file) command need to be added as well:
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nonDesign.StartCandidate.geometryName = StartCandidatestartCandidate |
Activate Automatic Non-Design Growth
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Sometimes this can lead to issues which are described here.
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Soft Symmetry
The soft symmetry is activated per default. It influences the design generation so that the part is symmetric in all three dimensions if they were symmetric in the respective dimension to begin with. This is achieved for geometrical symmetrical design spaces even without symmetric LBCs and the hard symmetry constraint.
Equivalence Delta Value:
This governs how far the optimization value of two symmetric elements is allowed to differ while still being considered equivalent. In theory any value works: the higher the value the more zealously the algorithm will try to keep Soft Symmetry, possibly degrading the quality of the produced geometry compared to a non-symmetric one. The default value is 1e-6.
Attempt Soft Symmetry:
Whether or not Soft Symmetry is attempted at all can be (de)activated here.
off: Soft Symmetry is deactivated.
always: Soft Symmetry is always on.
dynamic: The optimisation will start with Soft Symmetry activated but turn it off once no dimension’s symmetry can be salvaged. Note that “dynamic” will never turn it back on once it has turned it off once.
Soft Symmetry Threshold:
Specifies how many asymmetric voxels are sufficient for the "dynamic" setting of attemptSoftSymmetry to turn off soft symmetry. Values between 0 and 1 are allowed, where the number represents the proportion of voxels.
The default settings can be changed with the following commands:
configuration.equivalenceDelta = 1e-6 configuration.attemptSoftSymmetry = dynamic configuration.softSymmetryThreshold = 0 |
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You might also be interested in these tutorials:
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